Watershed Surface and Subsurface Spatial Intraflows Model

Abstract

We present new developments to the original, spatially lumped large basin runoff model (LBRM) of the National Oceanic and Atmospheric Administration’s Great Lakes Environmental Research Laboratory. In addition to making it a two-dimensional, spatially distributed model, we modify it to allow routing flows between adjacent cells upper soil zones, lower soil zones, and groundwater zones. We modify the LBRM continuity equations for these additional flows and add corresponding corrector terms to the original solution equations. We derive the flow network from elevation and hydrography and the LBRM automatically arranges cell computations. We apply the newly modified LBRM to the Kalamazoo River watershed in Michigan and to the Maumee River watershed in Ohio. The simulations show that the Kalamazoo River has dominant groundwater storage, allowing delayed and sustained hydrologic responses to rainfall whereas the Maumee River lacks any significant groundwater storage, allowing a fast flashy response to rainfall. These results are characteristic of the study watersheds, indicating that the addition of subsurface intraflows in the model has improved watershed representation.