Combining Chemical Mass Balance and Watershed Modeling in The Chippewa River Basin for Estimating Point and Nonpoint Pollution Sources.

Urban rivers are increasingly facing pollution challenges due to the complex interplay of point and nonpoint sources, complicating effective water quality management. This study focuses on the Chippewa River Basin (CRB) in Minnesota, aiming to assess annual pollutant loading and identify hotspots for pollution. Utilizing a combination of Chemical Mass Balance (CMB) analysis and the PLOAD model, the research evaluates pollutant contributions from various sources. The CRB, characterized by a continental climate and significant agricultural land use, presents unique challenges in pollutant load estimation. Water quality sampling from multiple monitoring stations revealed that nonpoint source pollution, particularly from agricultural activities, significantly impacts water quality. The study highlights the effectiveness of integrating CMB and PLOAD for estimating nonpoint source loads, demonstrating that localized pollutant export coefficients yield more accurate results than generalized coefficients. Findings indicate that the upper segments of the CRB experience lower nonpoint source impacts compared to downstream areas, emphasizing the need for targeted pollution management strategies. This research contributes valuable insights for future water quality management efforts in various regions.