Water quality in Changhu Lake is declining due to pollution from agriculture and aquaculture. To address this, a program called Total Maximum Daily Load (TMDL) was used to estimate the lake's pollution capacity and determine necessary pollutant reductions. The lake can handle 26,438.43 tons of COD, 90.78 tons of TP, and 1,815.56 tons of TN per year, but currently receives 14,137.74 tons of COD, 271.23 tons of TP, and 2,485.24 tons of TN annually. While COD levels are acceptable, TP and TN exceed safe limits. Non-point source pollution from agriculture and aquaculture is a major contributor to TP and TN levels, requiring targeted solutions for improvement.