Assessment Of Degraded Land In The Heihe River Basin, Arid Northwestern China

At present, land degradation is a most attention-getting problem on environment, which hasbeen affecting the world,s community and economy badly. China is one of the most serious landdegradation countries, where nearly one-third of the land is suffering from the threat of landdegradation. The Heihe River Basin, situated in arid inland of northwestern China, is one ofseveral areas severely affected by land degradation.This paper mainly based on the data including remote sensing, topographic maps and so onin Heihe River Basin, carries out the land degradation in Heihe River Basin using fuzzy patternrecognition method and statistical analysis functions of GIS, and analyzing the status of landdegradation connected with the various counties in the basin. Finally the land degradationprevention and controlling measures are brought forward in the light of aforementioned analysis.The main aspects of the study are as follows:(1) Based on the analysis of two remote sensing data on Heihe River basin, the status ofland use change is obtained, and the results indicate that the area of the arable land, woodlandand the urban land has all increased, but the lawn area and water area significantly reduces. Landuse changes in the way lead to land degradation of different types, which are the reduction ofwater resources, grassland degradation, decreasing of forest coverage, land salinization anddesertification.(2) Based on the existing research results and some field survey data, the main types of landdegradation of the Heihe River Basin are identified, which are soil erosion, drought, salinization,degradation of vegetation and desertification. The largest area of land degradation distributes inEjina, mainly including salinization and desertification, second is Sunan county, soil erosionmainly. Types of land degradation in general mountain counties are mainly soil erosion anddegradation of vegetation while land salinization and desertification in plain county areas.(3) In the guiding of index selection principles, the evaluation indicators of land degradationare investigated and determined, which includes vegetation cover, slope, soil moisture, salinity, indirectly change of water logging time, area of quicksand and dune, biomass of degradedgrassland.(4) The results of land degradation assessment show: the proportion of severely degradedland is the largest in Heihe River Basin, including mainly three types: water erosion,desertification and salinization; about84%of the mild degraded land distributed in Sunan, Jinta,Jiuquan, Zhangye of Gansu province, about67%moderately degraded land located in innerMongolia, and mainly in Ejina, about52%of the strength degraded land concentrated in Ejina,the rest is in inner Gansu province, including soil erosion and salinization.