THE UTILIZATION OF WATER RESOURCE AND ITS INFLUENCE ON ECO ENVIRONMENT IN THE NORTHWEST ARID AREA OF CHINA
WANG Gen xu CHENG Guo dong XU Zhong min(Lanzhou Institute of Glaciology and Geocryology,CAS,Lanzhou 730000)
The northwest arid area of China,having about 1/4 of the total area o f China,is located near the center of the Eurasian continent.There are many mounta ins with elevations of 4300-7000m,which scatter between plains feeding 676 inla nd rivers.In the late 50 years,the exploitation and utilization of water resourc es in those rivers have led to the formation of 390 07×104 ha of man made oas es that scattered all over the river basins,and built of about 622 reservoirs wi th a storage capacity of 65 5×108m3 The large scale utilization of water reso urces has not only facilitated the steady development of agricultural economy bu t also resulted in very serious impacts on eco environment in the arid area: (a) The runoff courses of most rivers were shorten ed and the terminal lakes were reduced or dried up.The water quality in the lower reach esbecame worsened.(b)Soil salinization and desertification became more and more s erious in these regions.The salinized area totalled about 210 18×104ha,and des ertified area about 674 93×104ha.(c)Vegetation has been seriously degraded or destroyed.The natural vegetated area was reduced by 49%-58%,grassland reduced by 16%-92% and degraded grassland area occupied about 52%.