Introduction:Purpose

GSSHA is intended to be a complete physics based wateshed analysis model and includes important processes related to the generation of runoff, stream routing, overland and stream sediment processes, and constituent transport. The primary purpose for the original version of GSSHA model is to correctly identify and realistically simulate the important hydrologic processes in watersheds. The model is intended to simulate different types of runoff production and determine the controlling physical processes in watersheds, i.e. infiltration excess, saturated source areas, and groundwater discharge. In addition, the model is to physically simulate soil erosion, transport and deposition, as well as constituent transport. Development of the model has been directed by the following requirements:

model must be capable of explicitly calculating flows, stream depths, and soil moistures in a variety of hydrologic regimes and conditions including non-Hortonian watersheds;
formulation must account for sub-surface effects on stream flow;
numerical algorithms must be robust;
model must conserve mass;
model simulates soil erosion, transport, and deposition;
model simulates contaminant transport problems;
simulation times must be short enough to allow real-time predictions for use at DoD training facilities;
model must be supported by the standard DoD graphical user interface (GUI) WMS;
source code must be available to the U.S. Army without restrictions or limitations on modification or publication of results.