The Routing Application for Parallel computatIon of Discharge (RAPID) is a river
network routing model. Given surface and groundwater inflow to rivers, this 
model can compute flow and volume of water everywhere in river networks made out 
of many thousands of reaches. 

For further information on RAPID including peer-reviewed publications, a manual, 
sample input/output data, sample processing scripts and animations of model 
results, please go to: 
http://www.ucchm.org/david/rapid.htm