AnnAGNPS Pollutant Loading Model
H. Hydrograph Development
Water reach routing consists of generating a hydrograph at the upstream end of the reach based upon the SCS unit graph method as described in NEH-4. Peak discharges are calculated using a procedure similar to TR-55 and a triangular hydrograph shape is substituted for the resulting non-linear shape, but the peak discharge & runoff volume are preserved. Nine rainfall distributions are included: (1) the four standard SCS Types (I, Ia, II, & IV); (b) a uniform for snowmelt & irrigation return flows; and (c) four especially developed for New Mexico. Other rainfall distributions are possible to develop at a later time.