ABSTRACT
ABSTRACT: With the effective control of Point Source (PS) pollution, Non-Point Source (NPS) pollution becomes the main cause of river water quality deterioration. Therefore, there is a need to identify critical nutrients and their loss potential. The objective of the study is to test the feasibility of SWAT (Soil and Water Assessment Tool) model as a simulator of nitrogen and phosphorus yields for the Laixi River basin in Lu County, then identify the key sources and critical areas of nutrient loss. Predicted values streamflow and NH3-N matched well with the observed values during calibration and validation (R2 ≥ 0.6 and Nash-Sutcliffe Efficiency ≥0.5). The result showed that NPS pollution was the absolutly major cause of water contamination with the maximal contribution rate 90%. The key governable source was fertilizer loss, followed by backyard livestock. Areas consisting in high percentage of farmland were critical areas of NPS pollution.
