干旱地区水资源评价和认识的若干问题——以新疆为例

干旱地区水资源的合理开发和国土整治规划有密切联系。本文以新疆为例,对干旱区水资源的正确评价、水资源开发如何利用自然优势、水资源的地区间调剂以及水文现象与生态环境变化的深入认识等问题,提出了几点探讨性意见,以供深入讨论。

ON THE EVALUATION AND UNDERSTANDING OF WATER RESOURCES IN ARID LAND

Water resources is a sensitive element for natural resources planning and territorial management in arid land. This article deals with some understanding of the evaluation and rational utilization of water resources in arid land. 1. The problems of correctly evaluating the water resources in arid land. The area of Xinjiang Uighur Autonomous Region is about 16.5% of China's total, but its annual flows (81 billion m3) is only 3.1% of China's total, its mean annual precipitations (145mm) and mean annual runoff depth (47 mm) equal 23% and 17% respectively to the average value of the country. It shows evidently that Xinjiang is arid land. But some papers compared only the annual flows between Xinjiang and other provinces or river basins, without considering the regional difference of the area and precipitation, and compared each other according to water volume per capita. The results from comparison show that water in the Xinjiang Uighur Autonomous Region rank the front row. Such material is not true and can not serve as the basis of the regional exploiting plan. 2. Using the advantageous natural conditions for rational development of water resources. The following are some examples: (1) Using intermont basin as underground reservoir may regulate a part of flood flow and decrease some reservoir investment for flood control. There are many such intermont basins in Xinjiang uighur Autonomous Region. (2) Seepage control for irrigation canals should be considered according to its necessity. If the canals in intermont basin or its major constituent of sediment content is clay, there is generally no necessity for seepage control. (3) It is necessary to build some mountain reservoirs to replace a part of plain reservoirs, which may increase the efficiency of flood control and irrigation benefit. 3. Adjusting the water resources between adjacent regions. It is important in arid land to divert a part of flows from the abundant water regions to the water deficient regions. There are three cases in Xinjiang Uighur Autonomous Region. (1) The Tarim River can naturally divert a part of its flows from the western part of the Tarim Basin to the eastern part. It will play a positive role in exploiting the natural resources and in the management of ecological environment of the eastern Tarim Basin. (2) A part of the Ertix River flows may be diverted through conveyance canal to the southern and southwestern pan of the Altay Area. It is possible in technique and rational in economy. We ought to plan and to realize. (3) Hi River has abundant flows, but it has some trouble in diverting water to the adjacent regions. At present, We can present some preliminary schemes or carry out some research work.4. Depth understanding of the changing cause of hydrologic phenomenon and ecological environment. For example, some papers consider that the cause of the buried "Silk road" and ancient oasis by sanddunes along the southern margin of the Tarim Basin, and the disappearance of the lake "Lop-nur" is due to climatic change in historical period. Practically, it is the consequence of human economic activities. It was more convenient then to divert river flow from the'middle reach than from the lower reach, hence the irrigated areas were naturally migrated from the lower reach to the middle reach, the oasis and road were abandoned, and gradually buried by sanddunes. In the recent 100 years, because of the large-scale reclamation of the Tarim Basin, the river flows were diverted into the new irrigated areas of the tributaries and its upper reaches, and the flows feeding the lower reach decreased year after year. It is the main cause of the disappearance of the lake "Lop-nur".