Simulating Seasonal Variations in Surface Water Bodies: A Catchment-based Land Surface Modeling Approach

Land surface models (LSMs) generally do not account for seasonal variations in lakes, rivers, wetlands, floodplains and other surface water bodies. Given the importance of these surface features in hydrologic and biogeochemical cycles, sediment transport and land-atmosphere exchange of trace gases, the seasonal variations in surface water bodies must be incorporated into LSMs for a better understanding of the hydrologic cycle and the Earth system. Towards this goal, we present a hydrologic catchment (watershed) based modeling framework with an explicit representation of lakes and river channels. Such a framework could be used not only for coupled Earth system studies but also to assimilate altimetric observations of stream and lake elevations, thus leading to a better estimation of water and energy fluxes. A catchment-based modeling template was developed for selected river basins using the Geospatial Streamflow Model from the USGS EROS Data Center. The grid-based NCAR Community Land Model (CLM) was modified to work on this catchment template. The CLM was further modified to incorporate streamflow through river channels and also temporal changes in lake surface area, resulting in a catchment-based modeling framework with a realistic representation of river channels and lakes. Here we compare grid-based simulations with the catchment-based simulations and also present other results from our model implementation.