Analysis of Water Quality Evolution Mechanism in the Maotiaohe Watershed
猫跳河流域水质演化机理研究

The Maotiaohe watershed is a typical mode of cascade hydropower development of rivers in China. Hydropower development has provided adequate power and clean water resources for the local areas over the past years. However, the water quality of the watershed has been deteriorative, which resulted in the loss of the clean freshwater provisioning function. Investigating the evolution mechanism of the water quality of the hydropower development can provide reasonable measures for the hydropower development in the future. First, total phosphorus and nitrogen data of Hongfeng Lake and Baihua Lake during the period 1980-2005 were collected for use in analyzing the deteriorating trend of the water quality in the study watershed. It was found that the watershed had experienced evolution trends of II-III-IV-V type since 1980. Second, correlation analysis of water quality data about Hongfeng Lake and Baihua Lake with data regarding social and economic situations for the upper reaches of the Maotiaohe River was performed to unravel mechanisms of water quality deterioration due to hydropower development. Results show that 1) extensive human activities in the upper reaches, involving an increasing number of population, the improvement of urbanization, and the extension of industrialization, are the primary causes of the water quality deterioration. 2) The discharge of sewage of rural residents and urban residents, and the growing use of chemical fertilizer are the direct causes for the water quality deterioration. Among the three major causes, the discharge of sewage of rural residents and the growing use of chemical fertilizer are the most significant factors making the water quality deteriorative. Finally, the authors made a comprehensive analysis of the hydropower development, the deterioration of water quality, and the water quality management. Results show that the Maotiaohe watershed has experienced hydropower development since the late 1950s. The deterioration of water quality occurred primarily from the 1980s to the 1990s. The water quality management was conducted from the mid 1990s to the present.