African Water Development Report 2006 - United Nations Economic ...

African Water Development Report 2006(f ) Data management: The software for thisfunction is often patterned after UnitedStates Environment Protection Agencydatabase systems which may contain programmesto:(i) Screen the input data;(ii) Fill in missing data, using regressiontechniques;(iii) Carry out statistical analysis of thedata;(iv) Generate synthetic series; and(v) Simulate hydrological processes.Research variety water software: Most of theseprogrammes are developed by universities, governmentresearch institutes, or large consultancies,often for a specific research project, and notfor general use. Organizations like the UnitedStates Army Corps of Engineers, the DelftHydraulics Laboratory, or the Danish HydraulicInstitute, just to name a few, routinely use alarge number of computer models that could beclassified as “research-related packages”. Theseinclude:different uses, at the very least, agricultural anddomestic water use. Another important distinctionbetween various river-basin models iswhether they are simulation models or optimizationmodels;(c)Flood control and floodplain management:There are two types of formulation of suchmodels which can be presented purely inphysical terms as hydraulic/hydrologicalprogrammes to determine the change andextent of flood patterns and also as economicor planning models that deal withthe effect of flooding on the floodplain users;(d) Reservoir operations: For reservoir operationsmodels, as for river-basin models, the distinctionbetween simulation and optimizationis important. The objective of reservoirmodels is to get the maximum amount ofbenefits out of a reservoir, given a time seriesof upstream inflows and downstreamdemands;(a) Watershed management and water balance:Most watershed models are composed of aset of the following elements depending onthe particular application:(i) rainfall-runoff;(ii) evapotranspiration;(iii) energy balance (if snowmelt is important)(iv) erosion;(v) runoff routing;(vi) transport of chemicals (nutrients, pesticides),and/or(vii) crop growth;(b) River-basin simulation and optimization:Watershed models deal with the part of the hydrologicalcycle from rainfall to the time whenthe water ends up in rivers or lakes. River-basinmodels deal with the different ways water can beused in a river-basin. They usually include somekind of storage in reservoirs, routing through ahydraulic network, and some representation of(e) Ground-water models: Ground-water modelsare generally large, and most are of the researchvariety. Some of the less complicatedpackages are offered commercially, usuallycosting more than $US 1,000 to start with.Ground-water models are either two-dimensionalor quasi-three- dimensional;(f ) Systems management: In recent years there hasbeen an increased interest in computerizingthe operation and maintenance of complexsystems such as irrigation systems or watersupply networks. A large number of componentelements generally make a systemcomplex;(g) Dynamic programming: Dynamic programming(DP) is a rather sophisticated optimizationtechnique that can handle prob1emsthat change over time or involving stochasticprocesses. In contrast, linear programmingis more adaptable to deterministic308