Thousand Island Lake Regional Ecological Risk Assessment

Qiandao Lake, located in Chun'an County, Zhejiang Province, is a large-scale artificial lake with diverse practical functions, such as electricity generation, flood prevention, and agricultural irrigation. It came into being as a result of the Xin'anjiang Dam project in early 1950's. Since China implemented the reform and opening policies in late 1970s, Qiandao Lake has been recognized as both a key national scenic area and a national forestry park. In 2001, it was further appraised as an AAAA tourist destination and a national ecological demonstration zone. However, due to the increased regional economic development, especially tourism development, Qiandao Lake is facing more and more severe threats from human activities.It is cf great importance to assess the emerging ecological risk in this area in order that the regional economy and ecological environment can co-develop in a harmonious manner. Under the direction of relevant ecological risk assessment theories, this study: assesses the current environmental situation of Qiandao Lake; makes a systematic data analysis of the water quality, acid rain and bottom mud in recent ten years; constructs the mathematical forecasting models of the ecological risk stress factors TN and TP; brings forv/ard the ecological risk management system, specifically risk management countermeasures and risk management technologies. Major conclusions are described as follows.The ecological environment quality of the Qiandao Lake region was assessed quantitatively with Year 2002 data. The result indicates that its water quality meets the drinking water standards. However, the acid rain issue of the Qiandao Lake region is serious. In some areas, the water has been polluted to some extent. The most significant water pollution factor is TN, followed by TP, potassium permanganate index, fecal coliform, and BOD5. The water quality analysis of the whole lake area shows that the pollutant load ratio of TN reaches as high as 50%, TP 17%, potassium permanganate index 12%, fecal coliform 9%, BOD5 8%, and rest items only 4%. The score of eutrophication assessment is 35.8, indicating that the water quality of the whole lake area has been in mesotrophic status. Moreover, other environmental pollution sources such as construction dust, lampblack, and noise are also comparatively prominent.A systematic analysis of the sources of ecological risk and the stress factors of the Qiandao region demonstrates that the major sources of ecological risk are agricultural pollution, urbanization, mining, point-source discharge, traffic and transportation, atmospheric sedimentation, tourism, stockbreeding and aquaculture, forestry, nonnative invasive species, floods, etc. Major regional risk stress factors are toxic chemicals, pathogens, and nutriments. Taking the changes of water quality as the endpoint of ecological risk assessment, this study brings forward the objectives of regional ecological risk management, i.e., keeping or improving the water quality, controlling the worsening of acid rain, resuming and increasing endangered species, guaranteeing electricity generation, flood prevention and irrigation, prolonging the reservoir's longevity, meeting the needs of entertainment and tourism, etc.According to the analysis of the comprehensive pollution index, in recent ten years most monitoring items and sectional pollution indexes demonstrate a notable declining tendency, which indicates that the water quality of Qiandao Lake is faced with relatively low risk. The comprehensive water pollution index comparisons among sections show that the sections of Jiekou, Hangtou Island, and Baimufan, which represent the three main water sources of Qiandao Lake, are the most serious three. The pollutants inputted through rivers are the primary threat of the water quality. Jiekou has the highest intensity of contamination input in normal years. Its index is significantly higher than that of other sections. The comparative analysis of the comprehensive pollution indexes of all monitoring items shows that the indexes of to...