What is it?
In instances where the groundwater head exceeds the land surface elevation, IGW-NET allows groundwater to the aquifer as a sink of water (i.e., groundwater is lost as surface seepage). This approach automatically captures the exchange of groundwater to surface water bodies as part of the robust solution process, as the surface water stages (elevations) are embedded in the high-resolution DEM datasets available on the IGW-NET server.How to use it:
Surface seepage is, by default, applied throughout the model domain (because in most places/cases surface water is naturally a sink of water from an aquifer). It is computed as the amount of hydraulic head exceeding the land surface (computed as aquifer head minus land elevation) multiplied by the leakancy (a factor representing hydraulic conductivity per unit thickness of the land surface). The default value is 1 (units: 1/d).To remove surface seepage as a possible sink of groundwater for topmost model cells, set the leakancy to zero.
Explicit Representation of Surface Water Bodies
Users can easily add streams/rivers, lakes and wetlands as line or zone features (e.g., as two-way head-dependent boundary conditions). IGW-NET also includes an Import Shapefile tool to add explicitly streams/rivers, lakes and wetland features as prescribed head or flux boundaries within a model (see the AquaNET Quick Tutorial on this ).(Warning: prescribing boundary conditions of this nature requires careful application by the user, without which significant errors in the regional water balance can occur (even though the flow patterns may be correct).Users can also auotimatically extract surface water features from the MAGNET4WATER DataCenter and add them as model features to the model (see Simulation Settings > Streams and Lakes from Data Center).