Analysis on situation of water environment in Wujiang District of the Taihu Lake

Human activities make significant impacts on water environments and can deteriorate environmental situation of water bodies. It’s remarkably important to control discharging pollutant into the environment. Our research team have conducted research on water environment in the Taihu Lake area in China. We carried out field investigation with sampling and measurement followed by analysis of our measurement data and obtained data from Suzhou local government in order to understand actual water quality situation and to prepare monitoring and regulation for better water environment protection.

Wujiang District, located in the southernmost tip of Jiangsu Province and Suzhou City, lies at the junction of Jiangsu, Zhejiang and Shanghai provinces, and is lower leach area of the Taihu Leke Basin. There’re rich forestry resources, natural stream systems, and flood control districts, which conserve water resources and water quality. Wujiang District has a population of 1.6 million, which supplies agricultural production and support industrial and economic development. Large amount of pollution can be potentially released to the lake area, and further deteriorate lake water situation and river environment. River network of Wujiang District is too complicated to understand pollution situation. Water domain covers 22.7% of the total area, small lakes and marshes are connected to each other by canal system. As the Taipu River is utilized as water resources for drinking water, water level is kept higher than connecting rivers and channels to avoid contamination from tributaries by controlling slice gates.

116 monitoring points were set at 66 river crossing points and in 50 marshes larger than 0.5 square kilometers. Monitoring data of water quality indicators include: pH, permanganate index, ammonia nitrogen, total nitrogen, total phosphorus, cyanide, sulfide, fluoride and some heavy metals. Chlorophyll a, COD, BOD, flow rate, water level, features of monitoring sites have also been investigated. Water quality have been monitored continuously by local government and measured once or twice per month by research team. Monitored water quality data since 2015 was presented by government, and sampling data since 2017 were measured for each parameter. Based on data analysis, pollution situation and mechanism have been discussed.

Higher COD was observed compared to BOD. It means that river water probably contains excess amount of non-biodegradable organic matters. Concerning to Total Phosphorus, they have no major differences in concentration and didn’t show distinctive tendency along the river flow. On the other hand, higher concentration was observed in lower leach regarding to Total Nitrogen even though water level was kept being higher than other water bodies. It’s suggested that there should be pollution sources within the area. And it’s also indicated where probable pollution sources are located. The area is flat terrain in the Yangtze Delta, and flow rate is extremely low. Changes in flow direction were observed, and it’s corresponding to tidal current. This makes it more difficult to understand situation, therefore modelling approach is prepared to assess water environment condition. Considering these analyses and discussion, we’re planning to continue further research to detect pollution sources and to understand situation in the area.