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Modeling Phosphorus Transport in an Agricultural Watershed Using the WEPP Model
Author(s) -
PerezBidegain Mario,
Helmers Matthew J.,
Cruse Rick
Publication year - 2010
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2010.0121a
Subject(s) - wepp , watershed , surface runoff , environmental science , hydrology (agriculture) , sediment , erosion , sediment transport , soil science , agriculture , soil conservation , geology , geotechnical engineering , ecology , computer science , paleontology , machine learning , biology
The Water Erosion Prediction Project (WEPP) model has been tested for its ability to predict soil erosion, runoff, and sediment delivery over a wide range of conditions and scales for both hillslopes and watersheds. Since its release in 1995, there has been considerable interest in adding a chemical transport element to it. Total phosphorus (TP) loss at the watershed outlet was simulated as the product of TP in the soil, amount of sediment at the watershed outlet, and an enrichment ratio (ER) factor. WEPP can be coupled with a simple algorithm to simulate phosphorus transport bound to sediment at the watershed outlet. The objective of this work was to incorporate and test the ability of WEPP in estimating TP loss with sediment at the small watershed scale. Two approaches were examined. One approach (P‐EER) estimated ER according to an empirical relationship; the other approach used the ER calculated by WEPP (P‐WER). The data used for model performance test were obtained from two side‐by‐side watersheds monitored between 1976 and 1980. The watershed sizes were 5.05 and 6.37 ha, and each was in a corn ( Zea mays L.)–soybean [ Glycine max (L.) Merr.] rotation. Measured and simulated results were compared for the period April to October in each year. There was no statistical difference between the mean measured and simulated TP loss. The Nash–Sutcliffe coefficient was 0.80 and 0.78 for the P‐EER and P‐WER methods, respectively. It was critical for both methods that WEPP adequately represent the biggest sediment yield events because sediment is the main driver for TP loss so that the model can adequately simulate TP losses bound to sediment. The P‐WER method is recommended because it does not require use of empirical parameters to estimate TP loss at the watershed outlet.