Abstracts

Integrated modelling exercises can help explain the linkages between the groundwater
system and surface water features. Understanding the role that geology plays in controlling
both the flow and storage of water is an important exercise that can be undertaken in any
sensitive watershed. This functional, hydrologic knowledge can provide the insight necessary
to develop both drought and climate change adaptation strategies.
272 - Balancing Near-Surface Water
Eric Soulis, James Craig, Bryan Tolson, Amin Haghnegahdar & Mateusz Tinel
Department of Civil and Environmental Engineering – University of Waterloo, Waterloo,
Ontario, Canada
The importance of lateral near-surface flow through weathered bedrock layers in hillslopes
or active layers in permafrost regions requires that, to be complete, a hydrologic model,
or a land surface scheme must have an interflow algorithm. Conceptual power law
extensions of a vertical drainage equation, such as Campbell or Brooks-Corey, generally
poorly parameterised interflow. The equations require several parameters that are difficult
to calibrate. At the opposite extreme of the complexity spectrum, are numerical solutions
of Richards Equation that are too cumbersome for meso-scale modelling.
This presentation will demonstrate a cleaner, easier approach: a power law expression using
effective saturation approximates the modeled outflow from a sloping confined aquifer.
The solution is a weighted combination of an expression for pure saturated and pure unsaturated
flow from the seepage base of the aquifer. The weighting coefficient is determined
from the soil pore-size distribution. The result is a Weibull-like expression that requires
only the SCS sand and clay fractions, along with valley slope and length. These parameters
are available in most models.
The method, called the Tilted Landscape Element (TILE) approach is suitable for surface
element in groundwater models or land-surface schemes. TILE has been implemented in
StandAlone— Modélisation Environmentale–Surface et Hydrologie (SA-MESH). The
method will be illustrated with examples from its use in SA-MESH.
IAH-CNC 2015 WATERLOO CONFERENCE
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