Study On Eco-environment Changes Of Shiyang River Basin In Recent Two Decades

The assessment of eco-environment quality is a systemic research work, and it is the important basis for the social and economic sustainable development planning and the eco-environment protection. Based on the analysis of the major ecological problems of Shiyang River Basin , using TM image, SRTM and meteorological element data, this thesis extracts several evaluation indices in the respects of land use, vegetation, climate and hydrology which are closely related with ecological system, calculates weighting coefficients of each evaluation index by principal component analysis method to construct the eco-environment evaluation model, and quantitatively evaluates and analyses eco-environment quality of Shiyang River Basin of 2006. By comparing to the eco-environment quality result of Shiyang River Basin of 1987, this thesis does a further research on how the eco-environment quality of this area changes in recent two decades. The conclusion of this paper is as follows.From the aspect of the present situation of the eco-environment quality in 2006:(1) Eco-environment quality of study region is totally between usual and poor, it has a banding distribution obviously from Qilian mountainous region in south along plain in central part to desert in north, except for some desert oasis in LiangZhou District and Minqin county.(2) Eco-environment quality of Tianzhu County, Sunan County in the upstream is well, eco-environment quality of Gulang County, Yongchang County, LiangZhou District is general, eco-environment quality of Minqin County, Jin-chuan, Ganzhou District and A La Shan League is worse, and eco-environment quality of A La Shan area is the worst.(3) In opinion of different ecological quality region distribution, Tianzhu County mainly contains grade 4 and 5 zones with largest percent of grade 4 zone, LiangZhou District, Gulang County mainly contain grade 3 and 4 zones with largest percent of grade 3 zone, Minqin County mainly contains grade 1 and 2 zones with the percent of grade2 zone accounting to 58%, Jinchuan District, Yongchang county mainly contains grade 2 and 3 zones, and there is a percent of grade 4 zone accounting to 13%.(4) During 121 towns in the study area, 24 towns belong to grade 2 zone, 67 towns belong to grade 3 zone, 29 towns belong to grade 4 zone, 2 towns named Duoshi town and Dachaigou town in Tianzhu county belong to grade 5 zone, the statistical figures shows that eco-environment quality of most towns is general.From the aspect of the changes of the eco-environment quality in recent two decades:(5) The difference of the eco-environment quality inside the basin tends to constant increasing, and the structure of ecological system becomes more instability.(6) The eco-environment quality of most regions in the upstream do not change significantly, while most regions in the middle and lower reaches get worse obviously, among which the eco-environment quality deterioration of Minqin County and A La Shan League shows the most serious of all, the transformation of eco-environment quality region presents from Level-two to Level-one.(7) The principal part of the eco-environment quality change are the regions which get worse obviously and have no change, their percents are 45.6% and 44.7% respectively. Meanwhile, there is little mount regions the eco-environment quality of which become better, the total percent only accounts to 2.52%. From the aspect of eco-environment quality change zones' distribution, the regions eco-environment quality of which become worse obviously are distributed in Minqin valley and A La Shan area, which are located at lower reaches of Shiyanghe river basin. Water resources shortage of these area is quite serious, and the natural ecological conditions become worse and worse in rencent 20 years, presented as decrease of vegetation coverage,sandy desertification and land salinization ,the disturbance of environment quality cased by human being is greater. These illustrates that eco-environment quality of research area declined in recent two decades is mainly caused by the deterioration of natural ecological conditions and human being's disturbance to ecological systems in Shiyang river basin.