ABSTRACT:

Excess Nitrate (N) and Phosphorus (P) in agricultural runoff can cause water quality issues like disproportionate eutrophication which can lead to depleted oxygen levels in water bodies. Implementation of Best Management Practices (BMPs) can help control the issue, however continuous monitoring and evaluation is essential to warrant a positive impact of the implemented BMPs. The objective of this 5-year (2014-2018) study was to compare the in-stream nutrient concentrations and load, both upstream and downstream with in a catchment that has high level of functioning BMPs. Linear Regression (LR) was used to assess temporal trends, and the significance of these trends was evaluated using the ANOVA analysis. The student's t-test was used for assessing spatial agreement/disagreement of the nutrient data. Results show that TSS load and concentration both are significantly higher downstream. Only monthly NO3-N concentration showed a significantly decreasing trend. The load of TSS (Upstream) and OP (Downstream) are significantly increasing for harvest season only. Overall, sediment and associated pollutants appear more sensitive to the intensity of rainfall in the late growing and harvest seasons. A more extended period of observed water quality and flow data are required to see any significant trend in phosphorus concentration.