Study On Desertification Evaluation Indices Of Shiyang River Basin

The Shiyang river basin is a continental river, which stretches over Qilian mountain, Hexi Corridor plain, north mountain region and Alashan plateau. Due to the deep influence of natural environment evolution and artificial activity, the ecological environment deteriorated day by day, and the serious ecocrisis has appeared, it is a typical case of ecology degradates in Northwest aridly continental river region. Mainly shown as following: Qilian mountains water conservation forest line rise, subterranean water level droped in the middle and lower reaches of Shiyang river, the earth's surface vegetation died, the natural oasis is shrinking constantly, the water resource of the whole basin is extremely short, the water contradiction is conspicuous among the use of live, production and ecological purpose, The desertificated land area is expanded day by day, the sandstorm is endangered and aggravated. The ecocrisis of Shiyang river basin not merely threaten the production and live of local people seriously, that is there are more than two million people face to lose their homes in Wuwei and Jinchang city, and also influence the ecologic safety of the important northwest strategic place Lanzhou city, and because its special geographical position, as one of the important birthplace of the northern sandstorm of our country, still influence the weather state of the whole northern area.The study was carried out through different nature, society, development and cause of reverse of desertification and then choose some representative place carried on typical investigation in Shiyang river basin, the factors that influenced the desertification were analysed, they were: vegetation coverage degree, slope, height of sand dune, shape of the earth's surface, erosion groove area proportion, soil quality, saline and alkaline spot occupation of land, covering sand thickness, harnessing engineering measures and sink rate of crop yield, etc. first the weightings and quantified numerical value were endued according to the influence of each factor, second the desertification degree was confirmed according to the fixed grade, last the corresponding area was calculated, thus set up desertification indice system. The translating signs were analysed through two issues of 1999 and 2004, and then verified especially on spot, the result indicated that the Shiyang river basin desertification area shows a tendency of development, and developed to the two poles, namely extremely heavy and light level increased slightly, middle and heavy degree reduced, this result unanimity with the prediction of some experts and actual conditions, so the system of desertification evaluation indice were certain effectiveness and practicability.