Inter-catchment groundwater transfer

[nickyrong]

Hi all,

In one of the applications, we want to allow upstream catchment to transfer groundwater to the downstream catchment.

The initial approach was to use:
:LateralEqulibrate RAVEN_DEFAULT AllHRUs SOIL[3] 100
:LateralEqulibrate RAVEN_DEFAULT DownAndUp1 SOIL[3] [mixing] INTERBASIN

However, this approach does not work because the lateral equilibrate is based on water level only. In cases where the water level is lower at the upstream catchment and the water level is higher at the downstream catchment, the lateral equilibrate function will transfer GW from downstream catchment to upstream catchment. It has been confirmed with Dr. Craig that Raven's lateral equlibrate does not use head and therefore does not consider elevations of the water.

We found a workaround by creating a new soil layer. The inter-catchment GW transfer rate from Upstream to Downstream subcatchment is being calibrated as percolation rate between the GW layer and the new "GW transfer" layer. The "GW transfer" water is then laterally flush to the downstream GW layer.

Nick Rong
Hydrologist at Knight Piésold Vancouver.