Large-Scale Watershed Delineation Strategy

The Agricultural Integrated Management System (AIMS) is a web-based portal utilizing existing USDA-ARS and NCCHE watershed and channel models with automated input data preparation needed in developing watershed management plans. One of the models to be implemented into AIMS is the USDA-ARS AnnAGNPS (Annualized Agricultural Non-Point Source pollution) model which uses sub-catchment and stream network data generated by the watershed delineation software TopAGNPS. In the current version of AIMS, reach data (stream network) and cell data (sub-catchments) were generated for the entire United States using default settings of TOPAGNPS and made available in AIMS as a new geospatial layer, instead of running TopAGNPS after each user request. To optimize the TopAGNPS simulations for the contiguous United States, a new watershed boundary dataset was developed by minimizing the total number of hydrological units to be processed and maximizing their total area. This is achieved by creating the network of HUC12 boundaries based on their hydraulic connectivity and grouping them based on a cumulative drainage area threshold. Thus, watershed boundary data of any size up to the prescribed area threshold can be generated. The delineation computations were distributed over a cluster of high performance computers to reduce the overall computational time and implemented as part of AIMS for easy application by any user.