Surface Water Interaction Modelling Using Visual MODFLOW and GIS

UNIVERSITY GHENTUNIVERSITEITGENTINTERUNIVERSITY PROGRAMMEMASTER OF SCIENCE INPHYSICAL LAND RESOURCESUniversiteit GentVrije Universiteit BrusselBelgiumGroundwater – Surface Water InteractionModelling Using Visual MODFLOW and GISJune 2008Promotor:Prof. F. De SmedtMaster dissertation in partial fulfilmentof the requirements for the Degree ofMaster of Science inPhysical Land Resourcesby: Jemaneh Shibru Wake

PHYLARES__________________________________________________________________________________________IACKNOWLEDGMENTI would like to express my heartfelt gratitude to my brother Y.S. Wake who has had the biggestinfluence in my life in being with me throughout my study in Belgium and to support my interestthroughout my stay.I would like to thank my promoter prof. F. De Smedt for his important suggestions. I am equallygrateful to doctoral students, A. Christian and G. Adem for their support, guidance, suggestionsand data provision.I like to thank all my class mates and staff members of PHYLARES at Ghent University and thedepartment of Hydrology and Hydraulic engineering of the Free University of Brussels for theirsupport and services.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARES__________________________________________________________________________________________IIAbstractUnderstanding interconnections among the components of the hydrologic cycle is fundamental todevelopment of effective water resources management and policy. The need to assess the effectsof variability in geology, climate, biota and human activities on water availability and flowrequires the development of models that couple two or more components of the hydrologic cycle.Groundwater and surface water resources are by no means disjoint, as knowing where surfacewater recharges groundwater and where groundwater flows supply surface water is an importantaspect of the hydrologic cycle. As global concerns over water resources and the environmentincrease, the importance of considering groundwater and surface water as a single resource hasbecome increasingly evident.Ground water and surface water are hydraulically interconnected, but the interactions aredifficult to observe and measure. In many situations, surface-water bodies gain water and solutesfrom ground-water systems and in others the surface-water body is a source of ground-waterrecharge and causes changes in ground-water quality. As a result, withdrawal of water fromstreams can deplete ground water or conversely, pumpage of ground water can deplete water instreams, lakes, or wetlands. Pollution of surface water can cause degradation of ground-waterquality and conversely pollution of ground water can degrade surface water. Thus, effective landand water management requires a clear understanding of the linkages between ground water andsurface water as it applies to any given hydrologic setting.At some reaches water moves from the land surface to the subsurface and in other areas it movesfrom the subsurface to the land. Lakes and wetlands can receive groundwater inflow throughouttheir entire bed, have outflow throughout their entire bed, or have both inflow and outflow atdifferent localities. In this thesis, surface water and groundwater interaction model wasdeveloped for a study area located in the Nete Catchment, Belgium.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARES__________________________________________________________________________________________Table of contentsAcknowledgment ............................................................................................................................ IAbstract .......................................................................................................................................... IITable of contents ......................................................................................................................... IIIList of figures ................................................................................................................................ VList of tables................................................................................................................................. VIChapter 1:Introduction ................................................................................................................ 11.1 General Overview ....................................................................................................... 11.2 Objective ..................................................................................................................... 21.3 Structure of the thesis.................................................................................................. 3Chapter 2:Approach and Methodology ...................................................................................... 42.1 General overview of Models ....................................................................................... 42.2 Groundwater models ................................................................................................... 52.3 Model Development.................................................................................................... 72.3.1 Model Objectives ................................................................................................... 72.3.2 Hydrogeological Characterization ......................................................................... 72.3.3 Model Conceptualization ....................................................................................... 72.3.4 Model Design ......................................................................................................... 72.3.5 Model Calibration .................................................................................................. 82.3.6 Sensitivity Analysis ............................................................................................... 82.3.7 Model Verification ................................................................................................. 82.3.8 Predictive Simulations ........................................................................................... 82.3.9 Performance monitoring Plan ................................................................................ 92.4 Methodology ............................................................................................................... 9Chapter 3:Interaction of groundwater and surface water ...................................................... 103.1 General overview ...................................................................................................... 103.2 Interaction of groundwater and stream ..................................................................... 123.3. Interaction of Groundwater and Lakes ..................................................................... 173.4 Interaction of Groundwater and Wetlands ................................................................ 173.5 Groundwater and Coastal Environments ................................................................. 183.6. Human activity and interaction of groundwater and surface water .......................... 18Chapter 4:Description of the study area ................................................................................... 194.1 Geographical location ............................................................................................... 194.2 Study boundaries and previous work ....................................................................... 204.3 Topography .............................................................................................................. 224.4 Hydrological setting ................................................................................................. 244.5 Recharge .................................................................................................................. 254.6 Land-use and Soil .................................................................................................... 254.7 Climate of the study area ......................................................................................... 25Chapter 5:Modeling tools ........................................................................................................... 275.1 ArcView GIS ............................................................................................................ 275.1.1 Introduction ........................................................................................................... 275.1.2 Types of data used in ArcView GIS ..................................................................... 275.1.3 Geographical data ................................................................................................. 275.1.4 Spatial data ............................................................................................................ 28III______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARES__________________________________________________________________________________________5.1.5 Image data ............................................................................................................. 285.1.6 Tabular data .......................................................................................................... 285.1.7. Extensions of GIS ................................................................................................. 285.2 Visual MODFLOW .................................................................................................. 295.3. Surfer 8...................................................................................................................... 305.4 Grapher 7 .................................................................................................................. 30Chapter 6:Model Setup .............................................................................................................. 316.1 Description of the Groundwater Flow Model ........................................................... 316.1.1 Model dimensions ................................................................................................ 326.1.2 Layers ................................................................................................................... 336.1.3 Elevation limits .................................................................................................... 346.1.4 Grid ...................................................................................................................... 346.1.5 Elevation data....................................................................................................... 346.1.6 Hydrogeological information ............................................................................... 366.1.7 Aquifer characteristics data.................................................................................. 386.1.8. Hydraulic conductivity......................................................................................... 416.1.9 River ..................................................................................................................... 416.2 Input to the model ..................................................................................................... 426.2.1 Recharge ............................................................................................................... 426.2.2 River ...................................................................................................................... 436.2.3 Constant Head boundary ....................................................................................... 446.3 Output from the model .............................................................................................. 44Chapter 7:Model calibration ..................................................................................................... 467.1 Calibration water levels ........................................................................................... 477.2 Calibrated Aquifer Parameters ................................................................................. 497.2.1 Hydraulic conductivity.......................................................................................... 497.2.2 Water levels .......................................................................................................... 49Chapter 8:Results and discussion .............................................................................................. 528.1 Output from the model .............................................................................................. 528.1.1 Model Water balance ............................................................................................ 528.1.2. Zonebudget ........................................................................................................... 558.3 Groundwater head ..................................................................................................... 568.3 Groundwater - Surface Water Interactions ............................................................... 58Chapter 9:Conclusions and Recommendations ....................................................................... 639.1 Conclusions ............................................................................................................... 639.2. Recommendations and future considerations ........................................................... 64References .................................................................................................................................... 65Annex ........................................................................................................................................... 68IV______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARES__________________________________________________________________________________________VList of figuresFigure 3.1 Flow through a Hypothetical aquifer system ........................................................ 11Figure 3. 2 Interaction of streams and ground water. .............................................................. 13Figure 3. 3 Effects of pumping from a hypothetical aquifer discharging to a stream ............ 15Figure 3. 4 The dynamic interface between ground water and streams. ................................. 16Figure 4. 1 Geographical Location of Belgium ...................................................................... 19Figure 4. 2 The study area and its location in the Nete Basin. ................................................ 21Figure 4. 3 Two – dimensional view and elevation of the study area. .................................... 22Figure 4. 4 3D of Topography ................................................................................................. 24Figure 4. 5 Slope map of the study area .................................................................................. 24Figure 6. 1 Model domain and units of measurement. ............................................................ 33Figure 6. 2 Bottom elevation for layer 1 ................................................................................. 35Figure 6. 3 Bottom elevation of layer 2 ................................................................................... 35Figure 6. 4 Bottom elevation of layer 3 ................................................................................... 36Figure 6. 5 Stratigraphy of the different aquifer units of the model. ...................................... 38Figure 6. 6 Geologic cross – section along the middle points of the model. .......................... 39Figure 6. 7 Geologic cross – section along the river flow route ............................................. 40Figure 6. 8 Two- dimensional view of the river segment in the model domain. .................... 41Figure 6. 9 Spatially distributed recharge ............................................................................... 42Figure 6. 10 Reclassified recharge zones and their values ....................................................... 43Figure 6. 11 Head values of layer 1 used for constant head boundary. .................................... 44Figure 6. 12 Location of the pumping wells ............................................................................. 45Figure 7. 1 Location of observation wells ............................................................................... 48Figure 7. 2 simulated versus field measured water levels ....................................................... 50Figure 7. 3 Scattergram for the measured versus simulated values ........................................ 51Figure 8. 1 The Volumetric water balance of the model. ........................................................ 53Figure8. 2 Volumetric water balance of the model in percentage of components. ................ 54Figure 8. 2 Zone 2 water balance ............................................................................................ 55Figure 8. 3 Ground water heads and flow directions in Layer 1 ............................................. 56Figure 8. 4 Equipotential head distribution of layer 2 ............................................................. 57Figure 8. 5 Equipotential head for layer 3 ............................................................................... 58Figure 8. 6 Cross section along column 328, groundwater flows to the river ......................... 59Figure 8. 7 Cross- section along row 185. Groundwater flows away from the river .............. 60Figure 8. 8 Position of the river water level and the groundwater level ................................ 61Figure 8. 9 North- South water table cross section along column 222. .................................. 62Figure 8. 10 General flow direction of groundwater within the model domain ........................ 62______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESIntroduction / ch.1__________________________________________________________________________________________1Chapter 1Introduction1.1 General OverviewWater covers two-thirds of the Earth’s surface and surrounds the planet in vapor form. Chemicaland density stratification during and immediately following accretionary heating of the Earth’sprimordial planetary body resulted in its present layered configuration. Internal heat andchemical reactions caused water, which was originally bound as oxygen and hydroxide inminerals, to diffuse from the Earth’s interior towards its surface. This degassing (still an ongoingprocess) of both water and other volatile species resulted in the accumulation and eventualcondensation of the fluid envelope of the Earth. Of course, water was also delivered to our planetby infalling comets and other H 2 O bearing planetesimals.The hydrologic cycle describes the complex system whereby water circulates among its variousreservoirs at and near the surface of the Earth. These reservoirs include the oceans, theatmosphere, underground water (including both soil water and groundwater), surface water(lakes, rivers and wetlands), glaciers and the polar ice caps. The Hydrologic cycle is directlycoupled to the Earth’s energy cycle, because solar radiation combines with gravity to drive theglobal circulation of water. This circulation, in turn, plays an important role in the heat balanceof the Earth’s surface. The hydrologic cycle is also closely linked to the geosphere and its rockcycle. Water erodes geologic materials, and the breakdown of these materials releases manychemical constituents that in turn define the chemical nature of the water. Water can also buildgeologic formations, through both chemical and mechanical depositional processes. Water isessential to all life forms in the planetary biosphere. (Mauricie, et.al, 2001).Only a small portion (3 %) of the water covering the earth’s surface is fresh. Of the fresh water77.5% is locked in ice fields and glaciers. Surface water and underground water are the utilizable______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESIntroduction / ch.1__________________________________________________________________________________________2fresh water resources of which groundwater water accounts for 95%; lakes, reservoirs, swampsand river channels 3.5%; and soil moisture comprises 1.5% (Freeze & Cherry, 1979).Understanding interconnections among the components of the hydrologic cycle is fundamental todevelopment of effective water resources management and policy. Ground water and surfacewater are hydraulically interconnected, but the interactions are difficult to observe and measure.In many situations, surface-water bodies gain water and solutes from ground-water systems andin others the surface-water body is a source of ground-water recharge and causes changes inground-water quality. As a result, withdrawal of water from streams can deplete ground water orconversely, pumpage of ground water can deplete water in streams, lakes, or wetlands. Pollutionof surface water can cause degradation of ground-water quality and conversely pollution ofground water can degrade surface water. Thus, effective land and water management requires aclear understanding of the linkages between ground water and surface water as it applies to anygiven hydrologic setting.In this work Visual MODFLOW 3.0 groundwater modeling package is utilized to quantifygroundwater – surface water interaction. Visual MODFLOW 3.0 package is an integratedmodeling environment for applications in three – dimensional groundwater flow andcontaminant transport simulations based on the finite-difference method.ArcView GIS has been used to store analyze and display the spatial data on topography, recharge,and in making the base map for the visual MODFLOW. Thus visual MODFLOW and ArcViewGIS have been used to simulate the ground water flow and consequently the flux between theground water and surface water.1.2 ObjectiveThe main objectives of this thesis work are to:• Develop a steady – state model and calculate the water balance of the area• Quantify the flux exchange between the ground water and the river in the study area( groundwater – surface water interaction)• Identify the loosing and gaining sections of the river______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESIntroduction / ch.1__________________________________________________________________________________________3Specific objectives of this thesis are:• Calibration and validation of the model• Development of a model to simulate groundwater flow in the study area and interpret theflow system using the developed model.1.3 Structure of the thesisThis thesis is organized into three major parts: literature review, methodology and discussion ofthe results and conclusion & recommendations. Chapter 1 is the introductory part which dealsmainly with the importance of the topic and the associated research questions. Chapters 2 and 3deal with literature review on past and existing knowledge about the topic of groundwatersurfacewater interaction and its importance in the study of hydrologic systems. Chapter 4focuses on the detailed description of the study area and available data for the modeling work.Chapter 5 – 8 discuss the modeling tools, procedure, calibration of the model and the resultsobtained. Conclusion and recommendation is presented in Chapter 9 on the ideas and issues forfurther work in the focus area.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESApproach and methodology / ch.2__________________________________________________________________________________________4Chapter 2Approach and Methodology2.1 General overview of ModelsModels are a substitute for a real system. Models are used when it is easier to work with asubstitute than with the actual system. Domenico (1972) defined a model as a representation ofreality that attempts to explain the behavior of some aspect of it and is always less complex thanthe system it represents. Wang & Anderson (1982) defined a model as a tool designed torepresent a simplified version of reality. Banks (1993) defines two types of models (1)consolidative: Consolidates facts regarding the system into a single model used as a surrogate tothe real system and (2) exploratory: a series of computational experiments to explore cause andeffect. Bredehoft et.al. Further subdivided ground water models into (1) Data driven exploratorymodels or “history matching” (2) policy question driven models and (3) conceptually drivenmodels.In studying a groundwater flow model we first develop a conceptual model descriptive of thepresent condition of a system. At this stage we identify relevant processes and physical elementscontrolling groundwater flow in the aquifer, namely: the Geologic framework, the Hydrologicframework, the Hydraulic properties, and the Sources & sinks (water budget) and determine datadeficiencies. Conceptual model dictates how we translate the real world to a mathematical Model.To make predictions of future behavior, a dynamic model is needed that is capable ofmanipulation. Mathematical models are one type of dynamic models and use equations torepresent the interconnections in a system. The simplest mathematical model of groundwaterflow is Darcy’s law. To apply Darcy’s law we need to have a conceptual model of the aquiferand to develop data on the physical properties of the aquifer system, the potential field and thefluid properties. The process of formulating and solving a mathematical model is referred to asmathematical modeling. The methods of obtaining the solution to a mathematical model can be______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESApproach and methodology / ch.2__________________________________________________________________________________________5broadly divided into two classes, analytical and numerical, even though the hybrid of these twoclasses is not uncommon. Analytical methods yield exact solutions to the governing differentialequations. Darcy’s law is an example of an analytical model. To solve an analytical model, onemust know the initial and boundary conditions of the flow problem. These conditions must besimple enough that the flow equation can be solved directly by using calculus.Numerical methods approximate the differential equations with a set of algebraic equations.These recast equations are numerical approximations and the answers obtained are alsoapproximations. The equations are most commonly in matrix form and they are solved on adigital computer, unlike analytical models which can be solved rapidly, accurately andinexpensively with a programmable calculator or a spread sheet on a personal computer.Generally, analytical solutions can be obtained under many simplifying assumptions, such as aunidirectional velocity field, a set of uniform transport properties, a simple flow domaingeometry, and a simple pattern of sink and source distribution. For this reasons, numericalsolutions which are capable of approximating more general conditions, are more widely used infield applications (Zheng & Bennett, 2002). This thesis is a numerical model to approximatesteady state water balance and interaction of surface and groundwater.2.2 Groundwater modelsGroundwater models are computer programs of groundwater flow systems for the calculation ofgroundwater flux and head. Because of the simplifying assumptions embedded in themathematical equations and the many uncertainties in the values of data required by the model, amodel must be viewed as an approximation and not an exact duplication of field conditions.Groundwater models, however, even as approximations are a useful investigation tool.For the calculations one needs (hydrological) inputs, (hydraulic) parameters, initial and boundaryconditions.The input is usually the inflow into the aquifer or the recharge, which variestemporally and spatially.Important parameters are the topography, thicknesses of soil and aquifer layers and theirhorizontal and vertical hydraulic condustivity, porosity and storage coefficient, capillarity of the______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESApproach and methodology / ch.2__________________________________________________________________________________________6unsaturated zone.Initial conditions and boundary conditions can be related to levels, pressures,and hydraulic heads on the one hand (head conditions), or to recharge, discharge, inflow andoutflow on the other hand (flow conditions).In general, groundwater models are conceptual descriptions or approximations that describe thegiven flow system using mathematical equations; they are an approximate descriptions of thephysical system or process. By mathematically representing a simplified version of ahydrogeological system, reasonable alternative scenarios can be predicted, tested, and compared.The applicability or usefulness of a model depends on how closely the mathematical equationsapproximate the physical system being modeled (model calibration).Application of existing groundwater models include water balance (in terms of water quantity),assessing the impact of changes of the groundwater regime on the environment, settingup/optimizing monitoring networks, setting up groundwater protection zones and understandingthe quantitative aspects of the unsaturated zone, simulating water flow and chemical migration inthe saturated zone including groundwater – Surface water interactions.Groundwater modeling begins with a conceptual understanding of the physical problem. Thenext step in modeling is translating the physical system into mathematical terms. Most modelssolve the general form of the three-dimensional groundwater flow equation which is acombination of the water balance equation and Darcy’s law:∂ ⎛ ∂h⎞⎜ Kx ⎟ +∂x⎝ ∂x⎠⎛ ∂h⎞⎜ Kyy ⎝ ∂y∂∂⎟ +⎠∂ ⎛ ∂h⎞⎜ Kz ⎟ ± W∂z⎝ ∂z⎠∂h= Ss∂t(1)Where,Kx, Ky, Kz are hydraulic conductivity values along the x, y, z axes [LT -1 ]h = hydraulic head [L]W = source/sink terms [T -1 ]Ss = specific storage coefficient [L -1 ]t is time [T].______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESApproach and methodology / ch.2__________________________________________________________________________________________72.3 Model DevelopmentA groundwater model application can be considered to be two distinct processes. The firstprocess is model development resulting in a software product, and the second process isapplication of that product for a specific purpose.2.3.1 Model ObjectivesModel objectives should be defined which explain the purpose of using a groundwater model.The modeling objectives will profoundly impact the modeling effort required.2.3.2 Hydrogeological CharacterizationProper characterization of the hydrogeological conditions at a site is necessary in order tounderstand the importance of relevant flow or solute transport processes. Without proper sitecharacterization, it is not possible to select an appropriate model or develop a reliably calibratedmodel.2.3.3 Model ConceptualizationModel conceptualization is the process in which data describing field conditions are assembledin a systematic way to describe groundwater flow and contaminant transport processes at a site.The model conceptualization aids in determining the modeling approach and which modelsoftware to use.2.3.4 Model DesignTo successfully transform a conceptual model into a mathematical model, it is necessary to havea database that provides adequate information to apply the requisite equations. All models startwith a groundwater flow model. For this, one needs to know the physical configuration of theaquifer. This includes the location, areal extent, and thickness of all the aquifers and confininglayers; the location of the surface water bodies and streams; and the boundary conditions of allaquifers.Important hydraulic properties include the variation of transmissivity or permeability and storagecoefficient of the aquifers, the variations of permeability and specific storage of the confining______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESApproach and methodology / ch.2__________________________________________________________________________________________8layers, and the hydraulic connection between the aquifer and surface- water bodies. Hydraulicenergy as indicated by the water table or potentiometric surface maps and the amounts of naturalaquifer recharge and natural stream flow are also needed. (Fetter, 2001).To model stresses on thenatural ground-water flow system, the modeler must know the locations, types, and amounts,through time, of any artificial recharge, such as results from recharge basins and wells or returnflow from irrigation, as well as the amounts and locations through time of ground-waterwithdrawals from wells. Changes in the amounts of water flowing in the streams and changes inthe water levels of surface-water bodies should also be known.2.3.5 Model CalibrationModel calibration consists of changing values of model input parameters in an attempt to matchfield conditions within some acceptable criteria. Model calibration requires that field conditionsat a site be properly characterized. Lack of proper site characterization may result in a modelcalibrated to a set of conditions that are not representative of actual field conditions.2.3.6 Sensitivity AnalysisA sensitivity analysis is the process of varying model input parameters over a reasonable range(range of uncertainty in value of model parameter) and observing the relative change in modelresponse. Typically, the observed change in hydraulic head, flow rate or contaminant transportare noted. Data for which the model is relatively sensitive would require future characterization,as opposed to data for which the model is relatively insensitive.2.3.7 Model VerificationA calibrated model uses selected values of hydrogeologic parameters, sources and sinks andboundary conditions to match historical field conditions. The process of model verification mayresult in further calibration or refinement of the model. After the model has successfullyreproduced measured changes in field conditions, it is ready for predictive simulations.2.3.8 Predictive SimulationsA model may be used to predict some future groundwater flow or contaminant transportcondition. The model may also be used to evaluate different remediation alternatives. However,______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESApproach and methodology / ch.2__________________________________________________________________________________________9errors and uncertainties in a groundwater flow analysis and solute transport analysis make anymodel prediction no better than an approximation. For this reason, all model predictions shouldbe expressed as a range of possible outcomes that reflect the assumptions involved anduncertainty in model input data and parameter values.2.3.9 Performance monitoring PlanGroundwater models can be used to predict the migration pathway and concentrations ofcontaminants in groundwater. Errors in the predictive model, even though small, can result ingross errors in solutions projected forwarded in time. Performance monitoring is required tocompare future field conditions with model predictions.2.4 MethodologyThe model construction is done by using the Visual MODFLOW 3.0 interface. To construct themodel, the study area was divided up into finite difference cells, which have a constant size of 5meter by 5 meter. In the vertical dimension, 3 groundwater layers were represented. Parametersrepresenting physical characteristics and flow conditions were attributed to each cell. VisualMODFLOW stores all of the data in a set of files. Most of the input files are stored in ASCII textformat. As a result, the input files can be manipulated using a text editor or even generated usinga FORTRAN or Visual Basic program. Visual MODFLOW then translates these data files to therequired format prior to running the models. By constructing the model, Visual MODFLOWcreates the modules, basic pieces of the program code, needed by the numeric engine.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________10Chapter 3Interaction of Groundwater and Surface water3.1 General overviewEach component of the hydrologic system is in continuing interaction with other components.Groundwater and surface water interact throughout all landscapes. As global concerns over waterresources and the environment increase, the importance of considering groundwater and surfacewater as a single resource has become increasingly evident and the interactions of ground waterand surface water have been shown to be a significant concern in water supply, water quality,and degradation of aquatic environments. (USGS, circular 1139).At some reaches water moves from the land surface to the subsurface and in other areas it movesfrom the subsurface to the land. Lakes and wetlands can receive groundwater inflow throughouttheir entire bed, have outflow throughout their entire bed, or have both inflow and outflow atdifferent localities.In order to fully understand the interaction between surface and ground-water flows, a detaileddescription of the budgets of all hydrologic components is necessary. Ground water is a majorcontributor to flow in many streams and rivers and has a strong influence on river and wetlandhabitats for plants and animals.The groundwater system as a whole is a three – dimensional flow field; therefore, it is importantto understand how the vertical components of groundwater movement affect the interaction ofgroundwater and surface water. A vertical component of a flow field indicates how the potentialenergy is distributed beneath the water table in the groundwater system and how the energydistribution can be used to determine vertical components of flow near a surface water body. The______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________11potential energy is also described as the hydraulic head – which is the sum of elevation and waterpressure divided by the weight density of water.The geology of an area governs movement and availability of surface and ground waters. Thepermeability of geologic materials and the intensity of precipitation determine the water flowsabove and below the land surface. Each geologic material exhibits its own permeability basedupon its chemical and structural composition.Much groundwater discharge into surface water is from local flow systems. Local flow systemsare the most dynamic and the shallowest flow systems; therefore, they have the greatestinterchange with surface water. Local flow system can be underlain by intermediate and regionalflow systems. Water in deeper flow systems have longer flow paths, but eventually discharge tosurface water and they can have a great effect on the chemistry of the receiving water.After rainfall events, materials with low permeability will cause water to pond whenever thewater input (recharge) exceeds the capacity of the materials to hold the water. Ponding of waterwill then cause water movement across the land surface and/or into the subsurface. Surfacemovement of water will follow elevation differences on the land surface, thus water willeventually spill into lakes, streams, rivers, etc. (Figure 3.1)Figure 3.1Flow through a Hypothetical aquifer system (GSFLOW model based on integration ofPRMS and MODFLOW 2005, Steven.L et.al USGS Techniques and methods 6-D1, 2008)______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________123.2 Interaction of groundwater and streamThe interaction between groundwater and streams takes place in three basic ways: streams gainwater from inflow of groundwater through the streambed (gaining stream), they lose water togroundwater (losing stream) or they do both, gaining in some reaches and losing in other reachesWoesner (2000) classified four types of interactions between a stream and groundwater: (1)gaining, where the groundwater flows into the stream; (2) losing, where the water in the streamdrains into the aquifer; (3) flow through, where the groundwater flows into the stream on oneside of the channel and out of the stream on the other side of the channel; and (4) parallel, wherethe groundwater flows in the aquifer beneath the stream and in the same direction as the streamwithout entering or leaving the stream. (Fetter, 2001)Generally, Streams either gain water from inflow of ground water (gaining stream; Figure 3.2 A)or lose water by outflow to ground water (losing stream; Figure 3.2 B). Many streams do both,gaining in some reaches and losing in other reaches. Furthermore, the flow directions betweenground water and surface water can change seasonally as the altitude of the ground-water tablechanges with respect to the stream-surface altitude or can change over shorter timeframes whenrises in stream surfaces during storms cause recharge to the stream bank. Under naturalconditions, ground water makes some contribution to stream flow in most physiographic andclimatic settings. Thus, even in settings where streams are primarily losing water to ground water,certain reaches may receive ground-water inflow during some seasons.Losing streams can be connected to the ground-water system by a continuous saturated zone(Figure 3.2 A, B) or can be disconnected from the ground-water system by an unsaturated zone(Figure 3.2C). An important feature of streams that are disconnected from ground water is thatpumping of ground water near the stream does not affect the flow of the stream near the pumpedwell.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________13Figure 3. 2 Interaction of streams and ground water. (Winter et.al, 1998.)In Figure 3.2, (A) represents gaining streams that receive water from the ground-water system,whereas losing streams (B) lose water to the ground-water system. For ground water to dischargeto a stream channel, the altitude of the ground water table in the vicinity of the stream must behigher than the altitude of the stream-water surface. Conversely, for surface water to seep toground water, the altitude of the water table in the vicinity of the stream must be lower than thealtitude of the stream surface. Some losing streams (C) are separated from the saturated groundwatersystem by an unsaturated zone.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________14A pumping well can change the quantity and direction of flow between an aquifer and stream inresponse to different rates of pumping. Figure 4 illustrates a simple case in which equilibrium isattained for a hypothetical stream-aquifer system and a single pumping well. The adjustments topumping of an actual hydrologic system may take place over many years, depending upon thephysical characteristics of the aquifer, degree of hydraulic connection between the stream andaquifer, and locations and pumping history of wells. Reductions of stream flow as a result ofground-water pumping are likely to be of greatest concern during periods of low flow,particularly when the reliability of surface-water supplies is threatened during droughts.At the start of pumping, 100 percent of the water supplied to a well comes from ground-waterstorage. Over time, the dominant source of water to a well, particularly wells that are completedin an unconfined aquifer, commonly changes from ground-water storage to surface water. Thesurface-water source for purposes of discussion here is a river, but it may be another surfacewaterbody such as a lake or wetland. The source of water to a well from a stream can be eitherdecreased discharge to the stream or increased recharge from the stream to the ground-watersystem. The streamflow reduction in either case is referred to as streamflow capture.In the long term, the cumulative stream- flow capture for many ground-water systems canapproach the quantity of water pumped from the ground-water system. This is illustrated inFigure 14, which shows the time-varying percentage of ground-water pumpage derived fromground-water storage and the percentage derived from streamflow capture for the hypotheticalstream-aquifer system shown in Figure 13. The time for the change from the dominance ofwithdrawal from ground-water storage to the dominance of streamflow capture can range fromweeks to years to decades or longer.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________15Figure 3. 3Effects of pumping from a hypothetical aquifer discharging to a stream (Heath, 1983, citedby USGS, Circular 1186)Under natural conditions Figure 3.3A, recharge at the water table is equal to ground-waterdischarge to the stream. Assume a well is installed and is pumped continuously at a rate, Q 1 , asin Figure 3.3B. After a new state of dynamic equilibrium is achieved, inflow to the ground-watersystem from recharge will equal outflow to the stream plus the withdrawal from the well. In thisnew equilibrium, some of the ground water that would have discharged to the stream isintercepted by the well, and a ground-water divide, which is a line separating directions of flow,is established locally between the well and the stream. If the well is pumped at a higher rate, Q 2 ,a different equilibrium is reached, as shown in Figure 3.3C. Under this condition, the groundwaterdivide between the well and the stream is no longer present, and withdrawals from the well______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________16induce movement of water from the stream into the aquifer. Thus, pumping reverses thehydrologic condition of the stream in this reach from ground-water discharge to ground-waterrecharge. In the hydrologic system depicted in Figure 3.3 (A) and (B), the quality of the streamwater generally will have little effect on the quality of ground water. In the case of the wellpumping at the higher rate in Figure 3.3 (C), however, the quality of the stream water can affectthe quality of ground water between the well and the stream, as well as the quality of the waterwithdrawn from the well. Although a stream is used in this example, the general concepts applyto all surface-water bodies, including lakes, reservoirs, wetlands, and estuaries.In gaining and in losing streams, water and dissolved chemicals can move repeatedly over shortdistances between the stream and the shallow subsurface below the streambed. The resultingsubsurface environments, which contain variable proportions of water from ground water andsurface water, are referred to as hyporheic zones (see Figure 3.4). Hyporheic zones can be activesites for aquatic life. For example, the spawning success of fish may be greater where flow fromthe stream brings oxygen into contact with eggs that were deposited within the coarse bottomsediment or where stream temperatures are modulated by ground-water inflow. The effects ofground-water pumping on hyporheic zones and the resulting effects on aquatic life are not wellknown.Figure 3. 4 The dynamic interface between ground water and streams. (Winter et.al, 1998.)______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________173.3. Interaction of Groundwater and LakesLakes, both natural and human made, are present in many different parts of landscapes and canhave complex ground-water-flow systems associated with them. Lakes interact with groundwater in one of three basic ways: some receive ground-water inflow throughout their entire bed;some have seepage loss to ground water throughout their entire bed; and others, perhaps mostlakes, receive ground-water inflow through part of their bed and have seepage loss to groundwater through other parts. Lowering of lake levels as a result of ground-water pumping can affectthe ecosystems supported by the lake diminish lakefront esthetics, and have negative effects onshoreline structures such as docks.The chemistry of ground water and the direction and magnitude of exchange with surface watersignificantly affect the input of dissolved chemicals to lakes. In fact, ground water can be theprincipal source of dissolved chemicals to a lake, even in cases where ground-water discharge isa small component of a lake's water budget. Changes in flow patterns to lakes as a result ofpumping may alter the natural fluxes to lakes of key constituents such as nutrients and dissolvedoxygen, in turn altering lake biota, their environment, and the interaction of both.3.4 Interaction of Groundwater and WetlandsWetlands occur in widely diverse settings from coastal margins to flood plains to mountainvalleys. Similar to streams and lakes, wetlands can receive ground-water inflow, recharge groundwater, or do both. Public and scientific views of wetlands have changed greatly over time.Wetlands generally were considered to be of little or no value. It is now recognized that wetlandshave beneficial functions such as wildlife habitat, floodwater retention, protection of the landfrom erosion, shoreline protection in coastal areas, and water-quality improvement by filtering ofcontaminants.The persistence, size, and function of wetlands are controlled by hydrologic processes (Carter,1996). Characterizing ground-water discharge to wetlands and its relation to environmentalfactors such as moisture content and chemistry in the root zone of wetland plants is a criticalaspect of wetlands hydrology (Hunt et.al, 1999).Wetlands can be quite sensitive to the effects ofground-water pumping. Ground-water pumping can affect wetlands not only as a result of______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESInteraction of Groundwater and Surface water / ch.3__________________________________________________________________________________________18progressive lowering of the water table, but also by increased seasonal changes in the altitude ofthe water table.3.5 Groundwater and Coastal EnvironmentsCoastal areas are a highly dynamic interface between the continents and the ocean. The physicaland chemical processes in these areas are quite complex and commonly are poorly understood.Historically, concern about ground water in coastal regions has focused on seawater intrusioninto coastal aquifers. More recently, ground water has been recognized as an importantcontributor of nutrients and contaminants to coastal waters. Likewise, plant and wildlifecommunities adapted to particular environmental conditions in coastal areas can be affected bychanges in the flow and quality of ground-water discharges to the marine environment.3.6. Human activity and interaction of groundwater and surface waterMany natural and human activities affect the interaction of groundwater and surface water. Theseinclude agricultural development, urban and industrial development, and drainage of the landsurface, modification to river valleys and modification to the Atmosphere.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________19Chapter 4Description of the study area4.1 Geographical locationBelgium is a small country in Western Europe bordering the North Sea, between France and theNetherlands (Figure 4.1) with a total area of 30,528 sq km (CIA world fact) covers a land area of30,278 sq km and water covers 250 sq km of the area. The geography of Belgium, with thegeographic coordinate of 50° 50'N, 4° 00’E, shows to have three different areas: lower Belgium(up to 100 m above sea level), Central Belgium (between 100 and 200 m above sea level) andUpper Belgium (from 200 to over 500m above sea level, with the highest point at an elevation of694 meters above sea level..Flanders is one of the three regions of Belgium and it is situated on the Northern part of Belgiumand covers an area of 13.524 km 2 (44% of Belgium), bordered by Netherlands and France.Among the major rivers of Flanders, Nete is one of them. Nete Basin covers an area of 1672.6km 2. The area used for the modeling in this thesis is found at the Eastern part of the Nete area,NE of Antwerp, Belgium.Figure 4. 1 Geographical Location of Belgium (from the World Atlas Map)______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________204.2 Study boundaries and previous workThe project site is a rectangular area with dimensions of 1.5 Km by 1.8 km. it represents a part ofthe Aa river Catchment (Fig 4.2).The study area is bounded on all four sides by no distinct landfeature topography or geological structure. The area is a cut - off from a large model. The modelarea is extending from 181181 m to 182981 meter on the Lambert co-ordinate system (West –East or X- direction) and from 210274 m to 211774 meter in the y-direction in the BelgianLambert co-ordinate system.The study area includes the boundary of the site, two weirs, 14 measurement points, five crosssection points and part of Aa river.The study has been performed by various sectors. The study on exchange processes in riverecosystems is a fundamental research project which is financed by FWO (Fonds voorWetenschappelijk Onderzoek- Vlaanderen). The project is promoted by the University ofAntwerp (UA) and performed by three universities, including the VUB and the University ofGent (UG). The project work dealt almost exclusively with the site at the Aa river near Poederleein northern Flanders. Piezometers have been placed to get a better view of the groundwater flowaround the site.A few distinctive interaction zones have been recognized, for which the exchange processes thenhave been investigated and modeled in detail. They are:• Interaction of shallow ground water with wetland or terrestrial ecosystems• Interaction of deep ground water with the water course• Interaction of shallow and/ or deep groundwater with the inundation area______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________21Kleine NetebasinStudy areaFigure 4. 2 The study area and its location in the Nete Basin.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________224.3 TopographyFigure 4.3 shows the contour of the Topographic elevations in the area. The highest points arefound at the Southeastern part and reach 21.88 meters while the lowest elevation point is locatedin the Southwestern part of the model and reaches 4.85 meters above the datum of the model.Three – dimensional view of the slope is shown in Figure 4.4 The slope of the elevation of thetopography is shown in figure 4.5.211600211400211200Y- lambert (m)211000210800210600210400181200 181400 181600 181800 182000 182200 182400 182600 182800X - Lambert (m)LEGEND14 Elevation contourObservation wellm0 100 200 300 400Figure 4. 3Two – dimensional view and elevation of the study area.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________23______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________24Figure 4. 43D of TopographyFigure 4. 5Slope map of the study area4.4 Hydrological settingSurface waterA 2.4 Km segment of the Aa river occurs in the study area. It flows through the study area fromthe North - Eastern to the South – Western ends. This river segment is gaining from groundwater in its upstream part and loosing in its downstream section (This is discussed in detail inchapter 8). The main Aa river has a total length of 36.7 Km with a drainage area of 23.7 km 2 .The average discharge is 1.74m 3 /s and average water depth is 1.15m and an average width of7.5m.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________25Ground waterThe regional aquifer underlying the area is preliminary the tertiary and Quaternary sands. Thedominant sources of recharge to the model area are precipitation in the winter, river leakage andconstant heads. Dominant mechanisms of discharge from the groundwater are drains, riverleakages and pumping wells.4.5 RechargeSpatially distributed recharge over the entire first layer of the model (in mm/y) was used in themodeling process. There were six reclassified recharge zones.4.6 Land-use and SoilIn general, the texture of the soil can be described as sandy loam, clay, loamy sand, andsand .The main land use types of the area are agriculture (50%), Meadow (17.29%), build up(1.98%) and coniferous forest (11.29%).4.7 Climate of the study areaFlanders has a temperate, oceanic climate. The average annual rainfall is 780 mm and theaverage temperature is 9.8 degree centigrade. Statistical analysis of the observed temperaturedata indicates January being the coldest month of the year with the average temperature of 5.8 °Cand august as the warmest month of the year with an average temperature of 18°C. However, thestudy area has a moderate average winter and summer temperatures of 5°C and 14°C, with windspeed of 3.27 and 3.84 m/s respectively.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESDescription of the study area / ch.4__________________________________________________________________________________________264.8 Available data1) Digital Elevation Model:The DEM with 5m by 5m grid size covering the whole study area was created by digitizing thetopographic contour map of the area.2) Meteorological data:The basic meteorological data requirement for running the model is recharge. These data wascollected from the previous works and the measurements on the Aa river.3) Flow data:Observed daily discharge data are taken from the measurement points of the Aa river. The flowdata is used for model calibration.4) Hydrogeologic and Geologic data:The geologic and hydrogeologic characteristics and parameters of the study area including thehydraulic conductivity ranges, bottom elevation of the layers is collected from previous works bySolomon T, 2006.5) Well data:Three pumping wells and 5 observation wells are identified in the area. Their location (X-Ycoordinate), average pumping rate and depth of the filter is available from the previous studiesand recent measurements from the study area.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModeling Tools / ch.5__________________________________________________________________________________________27Chapter 5Modeling toolsIn this chapter, the tools used for modeling of the study area are described. The first part dealswith ArcView GIS and in the second part, the three-dimensional groundwater modelingenvironment of waterloo hydrogeologic Inc, Visual MODFLOW is discussed.5.1 ArcView GIS5.1.1 IntroductionGeographical Information System (GIS) is a tool used to gather, transform, manipulate, analyze,and produce information related to the surface of the Earth, i.e. geographically referenced data.GIS is an information system where the database consists of observations on spatially distributedfeatures, activities or events which are definable in space. ArcView is a GIS software that allowscreating maps, and adding information. Using Arc View’s visualization tools, records fromexisting databases can be accessed and displayed on maps. ArcView GIS 3.2 is the revisedversion of 3.1.5.1.2 Types of data used in ArcView GISArcView GIS comes with a full set of ready-to-use general purpose data. For many applications,the data are used to create maps or are used as a base where data can be added.5.1.3 Geographical dataData that describes any part of the earth’s surface or the features found on it can be calledgeographic data. Geographic data from a variety of sources are used in ArcView. This includes______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModeling Tools / ch.5__________________________________________________________________________________________28not only cartographic and scientific data, but also land records, photographs, real estate listings,videos, etc. In fact a surprisingly large amount of information is geographic.5.1.4 Spatial dataSpatial data is the heart of every ArcView application. Spatial data is geographic data that storesthe geometric location of particular features, along with attribute information describing whatthese features represent. Spatial data is also known as digital map or digital cartographic data.5.1.5 Image dataImage data includes satellite images, Air photographs and other remotely sensed or scanned data.5.1.6 Tabular dataTabular data includes almost any data set, whether or not it contains geographic data. Someviews are displayed are displayed directly on a view directly; others provide additional attributesthat can be joined to existing spatial data. ArcView supports the following formats: i) Data fromdatabase servers such as Oracle, Ingres, Sybase, Informix, etc. ii) dBase III files iii) INFO tablesv) Text files with fields separated by tabs or commas. XY event tables are used in this project.5.1.7. Extensions of GISSome extensions of GIS used in the project re as follows:i) 3D Analyst3D Analyst is an extension that adds support for 3D shapes, surface modeling, and real timeperspective viewing to ArcView. Spatial data can be created and visualized with 3D analystby using a third dimension to provide insight, reveal trends, and solve problems.ii)GeoprocessingThe Geoprocessing is an extension which performs spatial analysis function in ArcView. Thewizard makes to walk through the desired theme to select for processing and allows selecting______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModeling Tools / ch.5__________________________________________________________________________________________29the name and location of the resulting output shape file. The following functions are providedin the wizard: a) Dissolve features based on an attribute b) Merge themes together c) Clip onetheme based on another d) Intersect two themes f)Assign data by location.iii)Grid analyst extensionIt is used to transform data from one form to another. This extension is used here to convertimage to grid theme, convert grid theme to x, y, z text file, and extract X, Y and Z values forpoint theme from grid theme.iv)Spatial AnalystThe ArcView Spatial analyst is an extension used to discover and understand spatialrelationship within a data. The main component of the spatial is the grid theme. The gridtheme is the raster equivalent of the feature theme. The spatial Analyst also representsgeneric spatial analysis functionality on grid and feature themes that is added to ArcView asan extension that is loaded with Extensions in the file menu when the project window isactive. The user interface components of the spatial analyst are loaded into the interface forviews.5.2 Visual MODFLOWVisual MODFLOW is the most complete and easy-to-use modeling environment for practicalapplications in three – dimensional groundwater flow and contaminant transport simulations.This fully- integrated package combines MODFLOW, MODPATH, zone budget,MT3Dxx/RT3D, and WinPEST with graphical interface. Visual MODFLOW is designed with amodular structure each dealing with a specified feature of the hydrologic system. VisualMODFLOW provides professional 3D groundwater flow and contaminant transport modelingusing MODFLOW-2000, MODPATH, MT3DMS and RT3D.Visual MODFLOW Pro seamlesslycombines the standard Visual MODFLOW package with WinPEST and the Visual MODFLOW3D-Explorer to give the most complete and powerful graphical modeling environment available.This fully-integrated groundwater modeling environment allows to:• Graphically design the model grid, properties and boundary conditions,• Visualize the model input parameters in two or three dimensions,• Run the groundwater flow, path line and contaminant transport simulations,______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModeling Tools / ch.5__________________________________________________________________________________________30• Automatically calibrate the model using WinPEST or manual methods, andDisplay and interpret the modeling results in three-dimensional space using the VisualMODFLOW 3D-Explorer5.3. Surfer 8Surfer is contouring software which easily and quickly converts grid data to contours and 3Dsurfaces, wireframe, vectors, image, shaded relief and post map. Contours of the topography and3D views of the geological cross sections in this report were produced with surfer 8.5.4 Grapher 7Grapher 7 is an easy-to-use technical graphing package to generate graphs quickly andeasily. With Grapher, creating a graph is as easy. One can change tick mark spacing, tick labels,axis labels, axis length, grid lines, line colors, symbol styles, and more. It is also possible to addlegends, bitmaps, fit curves, and drawing objects to the graph. The 2D geologic cross- sections inthis study were generated using Grapher 7______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________31Chapter 6Model Setup6.1 Description of the Groundwater Flow ModelThe steps of model construction can be summarized as follows (Pinder, 2002):1. Establish the minimum area to be represented by the model.2. Determine the hydrological features that can serve as boundaries to the model.3. Compile the geological information.4. Compile the hydrological information.5. Determine the number of physical dimension needed for the model.6. Define the size of the model.7. Define the model descritization.8. Input the model boundary conditions.9. Input the model parameters.10. Input the model stresses.11. Run the model.12. Output the calculated hydraulic heads.13. Calibrate the model.14. Make the production runs.The groundwater model boundary areal extent must be such as to incorporate all locations wheremodel heads are expected to change in response to stresses imposed on the model, incorporatethe area of interest to the client and to the extent possible coincide with an area defined bydistinct and easily evaluated hydrological boundary conditions.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________32The model area in this study is found within the Nete Catchment. The groundwater modelboundary encloses the main model domain which is part of a larger model domain for the NeteCatchment; it includes a segment of the Aa river flowing from the North Eastern to the Southwestern part of the model. It is bounded by constant head boundary along all its four sides.This ground-water model was developed using Visual MODFLOW 3.0. ArcView GIS 3.2software was also used for input data preparation and output data. The final model designfollows several model runs to best match field data with model results, also called modelcalibration (chapter 7). The conceptual model information is inserted into the mathematicalmodel and model choices are made to suit the data entered and output required. VisualMODFLOW requires model data to be entered as consistent units. Selected units are meters andday, except for recharge where mm/y is used.Model needs include:• Layers• Elevation limits• Grid• Recharge• Surface elevation• Bottom elevation• Groundwater pumping• Aquifer characteristics• River conductance• River bottom and stage6.1.1 Model dimensionsThe model area has a rectangular geometry and is 1.8 km from East to West and 1.5 km fromNorth to South (Table.6.1).Table 6. 1Geographic extent of the model.Easting Minimum 0 Easting Maximum 1800Northing Minimum 0 Northing Maximum 1500The geographic boundaries of the model domain are given in the Belgian Lambert co-ordinatesystem, and have a lower left corner co-ordinate at 181181 and 210274 as X and Y co-ordinaterespectively. These values were used as X min and Y min in the model setup window of Visual______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________33MODFLOW. Similarly, the upper right model corner is 182981 and 211774 for the X and Y coordinatesand these are used as X max and Y max in the model setup window of VisualMODFLOW (Fig 6.1).Figure 6. 1Model domain and units of measurement.The model framework, given in Figure 6.1 is summarized in Table 6.2.Table 6. 2Model ConfigurationCHARACTERSTICSVALUEMaximum model elevation21.88 mMinimum model elevation-88.75 mLayers 3Grid cell size5mRows 300Columns 3606.1.2 LayersThere are three model layers labeled 1 - 3 from top to bottom. Layer 1 is composed ofQuaternary sediments (HCOV 110 – 160) which comprise recent alluvium and Pleistocene sand.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________34Layer 2 constitutes the HCOV 230 hydrogeologic unit which is a Pleistocene and Plioceneaquifer system composed mainly of fine sand and clays. Layer 3 is comprised of HCOV 240(Pliocene clay layer) and HCOV 250 (Miocene sand aquifer). (Solomon T. 2007).6.1.3 Elevation limitsThe datum of the model is located within layer 2 of the model. The maximum model elevation is21.87 meters above the model datum and represents the highest point of the topography of themodel area. The greatest model depth is 88.75 meters below the datum of the model.6.1.4 GridThe model grid is 5 meters by 5 meters, evenly spaced throughout the model area in a North -South, East-West orientation. The model grid includes 300 rows and 360 columns.6.1.5 Elevation dataSurface and bottom elevations are entered to give model volume within the model perimeter.Surface elevations and bottom elevations data of the three layers were exported from ArcViewand imported into Visual MODFLOW.Importing surface and bottom elevationModel surface elevation values shown in Figure 4.3 were entered into the model as an xyz datafile. This surface elevation data was derived from an ASCII file by ArcView GIS. Similarly,Model bottom elevations of the three layers interpolated in ArcView were imported to the visualMODFLOW using the import elevation command. Figures 6.2 to Figure 6.4 show the elevationsimported.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________35Figure 6. 2 Bottom elevation for layer 1Figure 6. 3 Bottom elevation of layer 2______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________36Figure 6. 4 Bottom elevation of layer 36.1.6 Hydrogeological informationBecause of the close relationship between the hydrological properties of groundwater reservoirsand the geological characteristics of the materials that constitute the reservoir matrix, it is helpfulto focus on the nature and compilation of geological information.The model area consists of Quaternary and Tertiary sediments forming the Quaternary andCampine aquifer system, which is confined at the bottom by the Boom clay aquitard. Table 6.3lists the geological formations, based on the hydrogeological classification system for Flanders(Cools et al. 2006). Figure 6.5 indicates the stratigraphy of the layers and figure 6.6 and figure6.7 are geologic cross- sections across transects of North – South across a line connecting themiddle points of the two opposite boundaries of the model, and a cross section along the river.The quaternary (HCOV 0100), the Pleistocene and Pliocene (HCOV 0230), and the Miocene(HCOV 0250) aquifers are mainly composed of sand. These formations are semi-permeablebecause of the heterogeneous and irregular clay deposits. The Pliocene clay layers (HCOV 0240)occur in patches. The Miocene aquifer system (HCOV 0250) is the largest of the layers. In the______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________37local scale of the model of this study, the base of layer 1 is HCOV 160, which is sand. The baseof layer 2 is HCOV 230 and the base of layer 3 is HCOV250. Below HCOV 250, there is a clayaquitard known as the Boom clay aquitard.Table 6. 3 Main units of the HCOV hydrogeological code (Cools.et.al, 2006)Table 6. 4 Overview of aquifers on the HCOV classification for Flanders (Solomon T. 2007)Aquifer code(HCOV)Aquifer name0100 Quaternary aquifer/sand/0220 Campine clay-sandcomplex0230 Pleistocene andPliocene aquifer /sand/Total Hydraulic conductivity(m/d)1-105-154-400240 Pliocene clay layer 0.04-0.20250 Miocene aquifer/sand/ 3-30______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________386.1.7 Aquifer characteristics dataThe hydrogeologic layers of the model are bounded by clay aquitard at the bottom and recentalluvial deposits at the top. The steady state model requires the hydraulic conductivity of eachmodel layer.Figure 6. 5Stratigraphy of the different aquifer units of the model.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________39Figure 6. 6Geologic cross – section along the middle points of the model in the N – S direction.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________40Figure 6. 7Geologic cross – section along the river flow route______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________416.1.8. Hydraulic conductivityHydraulic conductivity zones vary widely in the area. The total hydraulic conductivity of eachHCOV layer is indicated in Table 6.4. (According to Solomon T, 2007), the total conductivity ofthe aquifers given in Table 6.4, were taken from a detailed hydro-geological study of the Flemishunderground (Envico 2002a; Envico 2002b; Haecon 2002), and from pumping tests preformedby Provincial and Intercommunal drinking water society of the Province Antwerp (PIDPA).6.1.9 RiverThe river in the model domain is the part of the Aa river (Figure 6.8). The river flows fromNorth-East to South West direction within the model domain. Aa river has an average dischargeof 1.74 m 3 /s, a water depth of 1.15 m and width of 7.5 m. Quantifying the amount of waterexchanged between this river and the groundwater of the area is one of the major objectives ofthis model. The river stage, river bed bottom elevation, river bed thickness and river conductancewere the data used for the surface water groundwater interaction modeling. The river boundarycondition package was used for data entry into visual MODFLOW.Figure 6. 8Two- dimensional view of the river segment in the model domain.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________426.2 Input to the modelWater enters the model domain through recharge, river leakage and constant head boundary.6.2.1 RechargeThe spatial distribution of the input recharge is shown in Figure 6.9. This data was reclassifiedinto six zones (Figure 6.10). The recharge ranges from 133.5 to 386.81 mm/ year. The averageannual recharge is about 261.33 mm/year. The recharge amounts to 17% of the groundwaterinput. Table 6.5 gives spatial distribution of recharge by zone of reclassification.Figure 6. 9Spatially distributed recharge______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________43Table 6. 5The ground-water model recharge and the annual recharge rate per zone.Recharge raterecharge m 3 /yZone Area (m 2 ) (m/y)1 10775 0.161 1734.7752 69100 0.199 13750.93 601900 0.25 1504754 1239350 0.289 358172.25 769825 0.318 244804.46 9050 0.351 3176.55Figure 6. 10Reclassified recharge zones and their values6.2.2 RiverRiver stage, river bed bottom elevation and conductance values were assigned to the riverboundary condition in the model. River leakage entering the groundwater system of the modeldomain amounts to 17% of the total input.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________446.2.3 Constant Head boundaryConstant head boundary input has the highest share and the values were taken from the values ofa model for the whole Nete Catchment (Figure 6.11). The constant head values were assignedonly to the cells at the model boundary. Constant head boundary contributes 66% of the input.Constant head boundary (m)Figure 6. 11Head values of layer 1 used for constant head boundary.6.3 Output from the modelConstant head boundary, river leakage, drains and wells constitute the means of groundwateroutput. Constant head consists of 11% of output, and river leakage consists 3% of the output.Groundwater discharge due to pumping through wells is the other means of output. There arethree pumping wells in the model domain. Pumping through these wells represents 1% ofgroundwater discharge. The steady-state model uses three pumping wells (Figure 6.12 and Table6.6). Pumping data was input to Visual MODFLOW manually. The required data were:• Well Name• Easting (X)______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel setup / ch.6__________________________________________________________________________________________45• Northing (Y)• Screen elevation interval (m)• Start (day)• End (day)• Rate (m 3 /day)Figure 6. 12Location of the pumping wellsTable 6. 6Location and pumping rate of the wells in the model domain.X Y Q ( m 3 /d)181900 211235 -5.2849182100 211350 -5.1671182682 211663 -2.6959Drains take the highest amount of discharge from the system. This represents 85% of thegroundwater discharging from the system.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel calibration / ch.7__________________________________________________________________________________________46Chapter 7Model calibrationModel calibration determines how well the model results simulate field measurements, such aswater level in wells and river gains and losses. In this iterative process, model value of inputparameters such as rain recharge and hydraulic conductivity are adjusted by trial-and-error tobest and reasonably match measured data.Minimum and maximum values possible for the conceptual model should not be exceeded incalibrating the ground-water model. Calibration is evaluated through the analysis of residualsdesigned to bring the mean of the residuals close to zero, and to minimize the standard deviationof the residuals. The calibration procedure may lead to different solutions for different parametercombination.The degree of fit between model simulations and field measurements can be quantified bystatistical means. Statistical analysis for calibration includes the Mean Error (ME), Meanabsolute Error (MAE); Root Mean squared Error (RMSE), and Normalized Root Mean SquaredResidual (Normalized RMS). Among these, the RMSE is generally the best calibration indicator(Anderson and Woesner, 1992). The error criteria are defined as the error between measuredhead and the simulated head.Mean Error is the mean difference between the observed head ( h0) and the simulated head (s)h .1n∑ME = ( h − )0n i=1h s(7.1)MAE is the mean of the absolute value of the differences in observed and simulated head.MAE =n1∑|h0 − h s|n 1i=(7.2)______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel calibration / ch.7__________________________________________________________________________________________47RMSE is the average of the squared differences in observed and simulated heads.n1RMSE = ∑ ( h0− h s)i2n i=1(7.3)The Normalized Root mean squared Residual is the RMS divided by the maximum difference inthe observation head values and is expressed by the equation.RMS− hNormalizedRMS = ( ) ( )maxh0 max s(7.4)NormalizedRMS is expressed as a percentage and is a more representative measure of thegoodness of fit than the standard RMS as it accounts for the scale of the potential range of thedata values.7.1 Calibration water levelsModel results have been calibrated with average water levels in 5 observation wells. The waterlevels and locations of the Piezometers are indicted in Table 7.1 and Figure 7.1.Table 7. 1 Water level and location of piezometers.Observation well name Lambert – X (m) Lambert –Y (m) Water level (m)VUB_N1 182186 211071 10.20VUB_N2 182040 211646 11.64VUB_S1 182468 210330 11.16VUB_S4 182942 210962 11.27De Schutt 182144 211295 10.68______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel calibration / ch.7__________________________________________________________________________________________48211600211400211200211000210800210600210400181200 181400 181600 181800 182000 182200 182400 182600 182800LegendObservation wellContour 0 100 200Figure 7. 1Location of observation wells______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel calibration / ch.7__________________________________________________________________________________________497.2 Calibrated Aquifer Parameters7.2.1 Hydraulic conductivityCalibrated hydraulic conductivities are shown in Table 7.2. The optimum hydraulic conductivityvalues for the various hydrogeologic units were taken from the literature (Solomon, T, 2006) andare indicated in Table --. Layer 1 was calibrated at a horizontal Hydraulic conductivity value of15 m/d and vertical hydraulic conductivity of 1.5 m/d. Layer 2 was calibrated at 6 and 0.6 m/d asthe vertical and horizontal hydraulic conductivities respectively. Layer 3 was calibrated at 5 m/dand 0.5 m/d for the horizontal and vertical hydraulic conductivities respectively. The initialvalues for the calibration of hydraulic properties were taken from past literature of Solomon T,2007.Table 7. 2Calibrated Hydraulic conductivity values for the three layersItem Layer 1 Layer 2 Layer 3Horizontal Hydraulic conductivity15 6 5(m/d)Vertical Hydraulic conductivity(m/d)1.5 0.6 0.57.2.2 Water levelsModel water levels and measured water levels are compared. Each red dot in Figure 7.2 plots anobservation well’s simulated water level with field-measured water level. A perfect match wouldplot along the blue line. The RMSE as seen is 0.094 meters.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel calibration / ch.7__________________________________________________________________________________________50Figure 7. 2simulated versus field measured water levelsAdditionally, it is important to show that there is no systematic error involved in the spatialdistribution of differences between modeled and measured heads. The simplest way to do this isto present a scattergram. Scattergram plot is produced with measured heads on the horizontalaxis, and simulated heads on the vertical axis, with one point plotted for each pair of data atselected monitoring sites as shown in Figure 7.3Figure 7.3 shows the linear regression plot of the measured and observed heads with a coefficientof determination (R²) calculated as 0.99, which indicates a very high degree of correspondencebetween the simulated and interpolated observations heads for the steady state.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESModel calibration / ch.7__________________________________________________________________________________________51Figure 7. 3Scattergram for the measured versus simulated values______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________52Chapter 8Results and discussionIn this chapter the results or the model output are discussed and their interpretation is presented.8.1 Output from the modelGroundwater leaves the system through river leakage, pumping wells, constant head and drains.Table 8.1 and Figure 8.1 show the water balance of the steady state model. The water dischargedto the river by the groundwater is about 385.15 m 3 /d. This is in the order of 3%.8.1.1 Model Water balanceOne of the methods of expressing model results is through a water balance. Water balance dataprovide both an indication of the relative magnitude of flow components as well as a means tocheck that the model solution has remained stable. If there is an error in the iterative solutionthen it is likely to show up in the water balance. External stresses such as wells, areal recharge,drain and river are simulated to calculate the water budget of the total area (Fig 8.1). Flowbudget calculated to show the difference between the inflow and outflow in the model domain isindicated in Table 8.1. The water balance results have shown discrepancies of 0.00%. Becausethis is a steady-state simulation, no change in storage occurs.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________53Figure 8. 1The Volumetric water balance of the model.Figure 8.2 presents the percentage contribution of each component. It can be observed that 66%of the input is from constant head boundary. The output is dominated by drain boundary whichaccounts for 85% of the outflow. River leakage consists about 17% of the input and 3% of theoutput.Table 8.1Input and output of the model in terms of volume.Item IN (m 3 /d) OUT (m 3 /d)Constant Head 7925.12 1362.86Wells 0.00 13.14Recharge 2090.46 ~0Drains 0.00 10282.02River leakage 2027.59 385.15TOTAL 12043.17 12043.18IN –OUT = -0.01 %Discrepancy = 0.00______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________54River leakage16.84INPUTRecharge17.3665.81Constant headOUTPUTRiver leakage3.198Constant head11.32Wells0.109185.38DrainsFigure8. 2Volumetric water balance of the model in percentage of components.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________55The flow budget shows a good result with 0.00% of discrepancy between inflow and outflow. Itcan be inferred that the water balance error is negligible. At this point, the simulation is ready tobe used for further applications of the model like contaminant transport simulation.8.1.2. ZonebudgetZone Budget calculates sub-regional water budgets using results from steady-state or transientMODFLOW simulations. Zone Budget calculates budgets by tabulating the budget data thatMODFLOW produces using the cell-by-cell flow option. The user simply specifies the subregionsfor which budgets will be calculated. These sub-regions are entered as 'zones' analogousto the way that properties, such as hydraulic conductivity, are entered. The sub-region overwhich the river flows was specified as zone 2 and the water balance of zone 2 was calculated asshown in Figure 8.3.Figure 8. 2Zone 2 water balance______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________568.3 Groundwater headThe head distribution output of the model is considered as an important hydrological parameterto characterize the flow system, in that it measures the energy of flow, and can also be used tocalculate the direction and rate of movement of the groundwater. Figure 8.4 indicates thegroundwater head and flow direction 1. From this figure it can be observed that flow is fromhigher heads which are on the Southeast and Northwest parts of the model to lower heads whichare mainly located around the river.Figure 8. 3 Ground water heads and flow directions in Layer 1Figure 8.4 to Figure 8.6 show the equipotential head distribution and flow direction ofgroundwater across the three layers of the model.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________57Figure 8. 4 Equipotential head distribution of layer 2______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________58Figure 8. 5 Equipotential head for layer 38.3 Groundwater - Surface Water InteractionsAquifers are often partially fed by seepage from streams and lakes. In other locations, thesesame aquifers may discharge through seeps and springs to feed the streams, rivers, andlakes. The exchange of flow between the aquifer and river at different locations has beenmodeled to find out the groundwater and surface water interactions. The interactions mainlydepend on the difference of the water level in the river and in the underground reservoir andaquifer materials in the river-banks and in the bed of the rivers. When the aquifer water level isnear land surface, seepage from the river is partially controlled by the height of the aquifer waterlevel. Activities or events that result in a lowering of the water table, such as ground waterpumping, induce more seepage from the river. Conversely, events that cause the aquifer waterlevel to rise (recharge events) will result in a decrease in river seepage. If aquifer water levelsrise above the level of the river, what was previously a losing river reach will become a reachthat is gaining water from the aquifer.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________59Figure 8. 6Cross section along column 328, groundwater flows to the river______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________60Figure 8. 7Cross- section along row 185. Groundwater flows away from the river______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________61Groundwater head and River water level positions12NE ( upstream)SW11.51211( Downstream)1110.510109.5998River stageRiverbedGroundwaetr head8.587.5770 500 1000 1500 2000 2500Distance (m)Figure 8. 8Position of the river water level and the groundwater head at differentlocations along the river flow path.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESResults and Discussion / ch.8_________________________________________________________________________________62Figure 8. 9 North- South water table cross section along column 222.The water table is generally parallel to the topography. The general flow direction of themodel is to the central part of the model (Figure 8.11).Figure 8. 10General flow direction of groundwater within the model domain______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESConclusions and Recommendations / ch.9_________________________________________________________________________________63Chapter 9Conclusions and Recommendations9.1 ConclusionsA steady state groundwater model has been developed by using Visual MODFLOW. Themodel water balance was calculated. The loosing and gaining reaches of the river wereidentified and the groundwater and surface water exchange was quantified. The inputparameters were taken from previous studies. In this approach, the distributed recharge,wells, vertical and horizontal hydraulic conductivity of the three layers, constant head,river, and drain boundary conditions were the inputs to the groundwater system. Thegroundwater level and the flow budget were calculated as outputs of the model.Calibration result shows that there is a good agreement between the measured and thesimulated values. Moreover, the pumping rate isn’t so high and, there is no significantinfluence of the pumping wells on the groundwater movement. The general flowdirection of the groundwater is from Northwestern and Southeastern part of the modelarea to the central part.Uncertainty of parameter estimates and boundary conditions may be the most significantlimitation. Slight alterations in parameters such as hydraulic conductivity and rechargecan lead to dramatic differences in model output. Similarly, boundary conditions stronglycontrol the flow regime, and so a poor representation can result in an inaccurate model.The model was calibrated in order to minimize the error on the model parameters andincrease accuracy of the simulation under steady state conditions by using hydraulicproperties of the aquifer based on previous studies of the area. The calibration resultswith the 0.094 meter root mean squared error agree quite well with the observed heads.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESConclusions and Recommendations/ch.9_________________________________________________________________________________649.2. Recommendations and future considerationsIn this work, modeling of groundwater – surface water interaction has been carried out ina part of the Nete Catchment using Visual MODFLOW and GIS tools.Simulation of the steady state condition of the groundwater system has been done.However, there are uncertainties in input parameters involved during the modelcalibration.The model has several limitations due to its assumptions. For example, because weassume steady-state conditions, we must ignore transient hydrologic processes. Theseinclude variably and intermittent pumping-well rates, as well as seasonal and annualfluctuations in river stage, precipitation, and evapotranspiration.To reduce these limitations as much as possible, the following improvements arerecommended for future modeling:1. Assigning accurate parameter values as much as possible (e.g., Kh, Kv).2. Perform transient-model runs. Transient simulations will help us to understandeffects of several influential factors, including pumping rate and seasonal riverfluctuations.3. Combine groundwater modeling with other methods of recharge – dischargecharacterization.4. Collect and evaluate data to improve critical components of the system such asthe aquifer and/or river boundary conditionsIn general, further studies which will enhance this model using more accurate data areneeded.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESReferences_________________________________________________________________________________65ReferencesAnderson, M.P. and Woessner, W.W., 1992. Applied groundwater modeling. AcademicPress, Inc., San Diego, California, 381 p.Anu Acharia, 2006. Test and Application of Groundwater – Surface water interactionmodel for the Aa, Msc Thesis - VUBBear, J., and A. Verruijt, 1987, Modelling groundwater water flow and pollution. D.Reidel publishing company, 441p.D.Smedt, Ground water hydrology course note.D. Smedt, Groundwater Modeling course noteDueker, 1979. Geography 176A Introduction to Geographic Information systems.Ernst W.G, 2000. Earth Systems, processes and issuesFetter, 2001. Applied Hydrogeology ( Fourth Edition )Ford A, 1999. Modeling the environment, an introduction to system dynamicsmodeling of environmental systemsFreeze and Cherry, 1979. GroundwaterFreeze, R.A. and Witherspoon, P.A., 1966. Theoretical analyses of regional groundwaterflow, Analytical and numerical solutions to the mathematical model. Water ResourcesRes. 2, pp. 641-656.Harbaugh, A.W., 1990. A computer program calculating subregional water budgetsusing results from the U.S. Geological Survey Modular Three- dimensional finite –difference Groundwater flow Model, Open file Report, pp. 90-392Heath, R.C., 1983. Basic groundwater hydrology. U.S. Geological Survey, Water Supplypaper 2220Hillel D (1998) Environmental Soil Physics. Academic Press, San Diego, CA______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESReferences_________________________________________________________________________________66Jensen SK, Dominigue JO (1988) Extracting topographic structure from digital elevationdata for geographical information system analysis. Photogramm Eng Rem S 54(11):1593-1600Jobson HE (1989) Users manual for an open-channel stream flow model based on thediffusion analogy. US Geological Survey, Techniques of Water Resources Investigations 89-4133Jon E. Hortness, Peter Vidmar, 2005. Surface-Water/Ground-Water Interaction alongreaches of the Snake River and Henrys Fork, Idaho. USGS, Report 2004 – 5115Julie Anne Ahern, 2005.Ground-water capture-zone delineation: method comparison insynthetic case studies and a field example on fort wainwright, AlaskaKollet, S.J., Maxwell. R.M., 2005. Integrated surface – groundwater flow modeling- Afree surface overland flow boundary condition in a parallel groundwater flow modelKonikow, L.F. and Reilly, T.E., 1999. Groundwater Modeling. The Handbook ofGroundwater Engineering. Boca Raton, CRC Press, pp. 20-1-20-40Kresic, N., 1997. Quantitative Solution in Hydrogeology and Groundwater Modeling.Lewis Publishers , Boca Raton, Florida, 461 pp.Lambs, Luc., 2003. Interactions between groundwater and surface water at river banksand confluence of rivers. Journal of Hydrology 288 (2004) 312-326McDonald, M.G. and Harbaugh, A.W., 1984. A Modular Three Dimensional Finite –Difference Groundwater flow Model-MODFLOW. US Geological Survey Open FileReport 83-875Mc Donald , M.G., and Harbaugh, A.W., 1988. A modular three dimensional finitedifference groundwater flow model. U.S. Geological Survey Techniques of WaterResources Investigations, 06-A1Pinder G.F , 2002. Groundwater modeling using GISSear, D.A., Armitage, P.D., Dawson, F.H., 1999. Groundwater dominated rivers. Dept ofgeography, University of Southampton, Highfield, Volume 13, Issue 3, pp. 255-276Solomon T, 2007. Spatio –temporal impacts of climate and land-use changes on theGroundwater and Surface water resources of a lowland Catchment______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESReferences_________________________________________________________________________________67Sophocleous, M, 2002. Interaction between groundwater and surface water: the state ofthe science. Hydrogeology Journal, 10:52–67Steven L, Richard G, R. Steven, David E, and Paul M, 2008. GSFLOW—CoupledGround-Water and Surface-Water Flow Model Based on the Integration of thePrecipitation-Runoff Modeling System (PRMS) and the Modular Ground-Water FlowModel (MODFLOW-2005)Todd, David K. 1980. Groundwater Hydrology. 2nd Edition. New York: John Wiley &SonTom Brooks, 2006. Heretaunga Steady-State Ground-Water ModelWaterloo hydrologic, 2002. Visual MODFLOW v.3.0.0 User’s Manual, Ontario, CanadaWinter, T.C., 1995 .Recent advances in understanding the interaction of groundwaterand surface water, Reviews of Geophysics,33( supplement): 985-994Winter TC, Harvey Jw, Frank OL, Alley WM, 1998. Groundwater and Surface water asingle resource, US geological Survey Circular 1139. http://pubs.usgs.gov/circ/circ1139Winter, T.C., 1999. Relation of streams, lakes, and wetlands to groundwater flowsystems. Hydrogeology Journal 71, pp. 28-45Woesner WW, 2000. Stream and fluvial plain groundwater interactions: RescalingHydrogeologic thought. Groundwater 38(3): 423-429World Atlas, http://www.worldatlas.com/webimage/countrys/europe/be.htmZheng and Bennet, 2002. Applied Contaminant Transport modeling ( Second edition)______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESAnnex_________________________________________________________________________________68ANNEX3D view of the model and its three ayers______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESAnnex_________________________________________________________________________________69Wells and their location, the 3 larger wells are pumping wells and the rest are piezometers.______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESAnnex_________________________________________________________________________________70Hydraulic conductivity values assigned to the three layers______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESAnnex_________________________________________________________________________________71Water table cross section along column 80______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESAnnex_________________________________________________________________________________72Water table cross – section along row 108______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS

PHYLARESAnnex_________________________________________________________________________________73Water table cross-section across column 301______________________________________________________________________________________Groundwater – Surface water interaction modeling using visual MODFLOW and GIS