Uncertainty analysis of watershed pollution loads: application to Tangxun Lake

Evaluation of pollutant loads and the corresponding source apportionment is key information for water quality-quantity management of lake watersheds. Source apportionment is the estimation of contributions by different sectors or areas to the lake aquatic environment. Taking the Tangxun Lake in southeast of Wuhan as a case study, this paper first develops an integrated model to assess major pollutants of total nitrogen (TN) load coming from different land-based activities based on statistics and monitoring data. Given the uncertainty and variability in model input parameter values, watershed-scale water pollution load calculation can result in significant uncertainty, and evaluating this uncertainty is important for policy makers who refer to the simulation output for lake watershed management decision-making. With the Monte Carlo sampling method, the possible load ranges are given and critical parameters are identified. In general, this study provides guidance for future research on parameter sensitivity and uncertainty in watershed pollution load apportionment and related management strategies.