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How can I model infiltration (seepage, flow loss) of water from a pond into the surrounding soil? Which seepage methods are available for each numerical solver? Is evaporation modeling supported?
Ponds can lose water by seepage (infiltration/exfiltration into the groundwater) or by evaporation. Any water lost by seepage or evaporation does not show up in downstream links and the flow is considered as lost from the system. In the properties of a pond element you will see the attribute called "Pond Seepage Method" in the "Infiltration/Inflow & Seepage" section. You can choose between a few different methods depending on which numerical solver you are using.
By default, "None" will be selected which means no flow loss/seepage is modeled.
Implicit and GVF-Convex solvers:
Note: Pond Infiltration is ignored when the pond is not connected to an outlet structure. See: No seepage results from pond in SewerGEMS or CivilStorm
In applying either method, the models also has a stability filter when the pond water depth is below 0.5 ft so that the seepage loss rate will linearly reduce to zero as the depth decreases to zero.
Explicit (SWMM) solver:
Pond infiltration losses can be viewed in a few different ways. First, you can view or graph the attribute "Flow (Seepage Loss)" for your pond. Alternatively, you can view the volume of infiltration loss in the "Ponds" tab of the Hydraulic Reviewer.
If none of these methods are suitable for your situation, you can use the approach of modeling the infiltration/seepage with a user defined rating table (varying flow as a function of headwater elevation) on a separate pond outlet structure. Meaning, a pond outlet node connected to the pond, with a downstream conduit connected to a free outfall, and the composite outlet structure for the pond outlet node configured with the User Defined Rating Table component.