Advances in groundwater representation at the subgrid scale in Land Surface Models: an approach based on HAND (height above nearest drainage)

Abstract:

Groundwater lateral flow at the local scale from hilltops to valleys is responsible for much of the variability in water table depth across the landscape at the regional scale. This variability in water table depth related to small scale topography (shallow in valleys, deep under hilltops) creates patterns in soil moisture, water accessibility to vegetation, and ultimately in land surface fluxes that can impact atmospheric dynamics. The organization of such patterns occurs at a scale that is usually not resolved by Earth System Models, which commonly run at resolutions of tens of kilometers. We present here some examples of groundwater representation at the subgrid scale in Land Surface Models based on a grid cell partition in zones according to HAND (height above the nearest drainage). These zones at different slope positions reflect the contrasting water table depth conditions within a grid cell related to local groundwater flow, thus offering a promising approach in the modeling of the heterogeneity of hydrologic setting at the local scale in LSMs.