Research On The Response Of Water Quality To Human Activities In Shuangta Reservoir, Chang Mahe River Basin

Based on the special natural climatic conditions in the Chang Mahe basin, data sets of human activities and land-use variability within 1993-2008 were selected from Guazhou and Yumen, as well as water quality data from Shuangta reservoir within the same period. By using these data above, a series of principal component analysis (PCA) and multiplex linear regression analysis were carried on in order to explore how human activities can affect water quality in this watershed. After PCA, the most representative factors of human activities and water quality which were used to the multiplex linear regression analysis were selected. Corresponding linear regression equations were established subsequently. These equations were between human activities of different region scales and water quality in Shuangta reservoir, these scales were Guazhou, Yumen and the total Changma river watershed, separately. The relationship of these equations quantificationally wree analyzed. From regression equations, agricultural activity, especially fertilizer application amount, is the dominant effective factor resulting in the variability of water quality in the reservoir. There still exists the potential of eutrophication. As to the industrial activities' effects to water quality, there are no obvious responses in these equations. For the main factor resulting to the variation of water quality in the reservoir, on the one hand, was the increase of pollutants load capacity within the basin. It had a direct relationship with human activities such as the increase of arable land areas, development of saline land, the increase of irrigational drainage (e.g. the development of saline land in the Qiaozi and the surroundings of Shuangtabao in the upstream of the reservoir as well as the increasing irrigational drainage around the reservoir) and the increase of fertilizer application amount. In addition, there were close relationship between water quality and city pollution discharge, domestic sewage as well as industrial activities caused by pollution increase. On the other hand, because of the decrease of reservoir inflow and the relative improvement of pollutants load capacity entering the reservoir and river, the values of PH, permanganate index and COD were increased, while the dissolved oxygen decreased.Under the consequence of other conditions unchangeable, when farmland area increases by ten thousand acres in Guazhou, then PH will increase by 0.119, dissolved oxygen will decrease by 0.125, permanganate index will increase by 0.417, COD will increase by 0.769. When fertilizer application amount increases by ten thousand tons inYumen, so Ph will increase by 0.069, dissolved oxygen will decrease by 0.126, permanganate index will increase by 0.962, COD will increase by 0.36. Meanwhile, an improved PCA and the surface water quality standards to assess water qualities of Shuang Ta reservoir were combined, Chi Jinxia reservoir and Dang He reservoir, at the same time we analysed the reasons of changes in water quality. Finally water quality in Shuang Ta reservoir was predicted using an improved BP model by adding momentum items. Research results show that water quality will be classified to stageâ…¡five years later and the quality is well enough to be satisfied with the domestic use and agricultural irrigation standards. According the relationship between human activities and water quality, as well as the prediction results of water quality, we proposed the controlling measures of decreasing the human activities'effects on water environments in Chang Mahe watershed.