Impacts of Upstream Input and Local Pollution Loads on the Water Quality of Suzhou Creek Based on Mathematical Models

Abstract

Suzhou Creek, a river in Shanghai of China, was severely polluted several years ago. Since the Suzhou Creek Environmental Rehabilitation Project was launched in 1998, its water quality has been improved substantially. The “black and stink” phenomenon has almost been eliminated. However, the upstream input and local pollution loads are significantly affecting the water quality of Suzhou Creek. As for these two factors, some heated debates on which one has a greater impact never stop. This work was to quantitatively analyze and forecast the impacts of the two influential factors based on both USGS's FEQ and USEPA's WASP models. The data from the Third Trial Low Flow Augmentation on Suzhou Creek in 1999 and other monitoring results were used to calibrate and verify the model parameters. Based on mathematical model, the impacts of upstream input and local pollution loads were analyzed; furthermore, the water quality of Suzhou Creek was predicted based on the assumption that the upstream quality was improved by one class and the tributary quality met Class V of National Surface Water Quality Standards. Results indicate that if the water quality of upstream input is improved by one class, the water quality of the upstream segments of Suzhou Creek will be improved more than that of the downstream segments. In contrast, if the tributary quality meets Class V of National Surface Water Quality Standards, the water quality of the downstream segments of Suzhou Creek will be improved more than that of the upstream segments. For Suzhou Creek to meet Class V of National Surface Water Quality Standards, it is necessary to reduce the local pollution loads and to improve the water quality of upstream input.