Book Description

Models are developed for predicting daily sediment, phosphorus, and nitrogen yields from small watersheds; routing the yields through large watersheds; and determining the optimal operating policy of the large watershed. Sediment yield prediction with MUSLE is refined by dividing subwatersheds into land capability classes to determine the linear factors. The phosphorus and nitrogen yield models, based on loading functions, are adapted to individual storm prediction by simulating nutrient concentrations in the soil, using daily predicted sediment yields, and computing enrichment ratios. Phosphorus and nitrogen balance models are developed to predict daily nutrient concentrations in the soil. The nitrogen balance model is also used in predicting nitrate yield. The routing model is based on sediment routing and phosphorus and nitrogen loading functions. Sediment routing is refined by replacing the median sediment particle size with the entire particle size distribution. Also the routing coefficient is determined for each reach instead of using one routing coefficient for the entire watershed as in the original method. Phosphorus and nitrogen routing is accomplished by using the routed particle size distributions to calculate enrichment ratios for the loading functions. Nitrate in the runoff is considered a conservative material for the duration of an individual flood. SPNM, a problem-oriented computer language is developed to make routing more convenient. SPNM is designed to predict sediment, phosphorus, and nitrogen yields for individual storms on small watersheds and to route the yields through large watersheds.