Study On The Characteristics Of Water Environment And Reasonable Utilization Of Water Resources In Daquan River

Daquan River lies in the south region of the Dunhuang basin, the west part of Hexi corridor. It flows into the basin of Dunhuang by the front of Mogao Grottoes, and belongs to the water system of Shule River. Compared with the other rivers of Hexi corridor, Daquan River is just a small inland river, but its existence has important contact with the rise and fall of Dunhuang Mogao Grottoes which is famous all over the world. It is the fountainhead of Mogao Grottoes to choose the site and construct with the development. Up to now, this river is still the main sources for greening, also provides the irrigation water for the sand biologic control engineering. It has big effects for the protection of the Grottoes cultural relic. However, in summer, the flood of Daquan River caused by the rain-storm affects the safety of the Grottoes cultural relic seriously. Therefore, to study the characteristics of water environment of Daquan River, to understand its runoff characteristics and its time-space change regulations, have the important meaning for protecting the historical and cultural heritage of Mogao Grottoes. At the same time, it can provide the technical support for protecting the unique natural river water environment in Mogao Grottoes area and the reasonable utilization of the precious water resources in the desert district.By field investigation, discharge measurement on the spot and sampling, synthesizing and analyzing the data, the characteristics of the river basin of Daquan River and the time-space change regulations of the runoff and water quality are discussed and summarized for the first time. The results show that Daquan River is a small river basin in the very dry desert district;with complicated terrain, big headstream area, and short flow path as its main river basin characteristics. The space distribution characteristics of the runoff take on as the runoff in south source area is small;the runoff in middle reaches increases gradually;after the mountain pass the runoff decreases gradually till disappearance. The annual and seasonal changes are smaller, but the daily variation of the runoff in summer is very notable, this is the special characteristic of the runoff of small rivers in very arid desert district. Thenotable daily variation of the runoff is the result of the natural high strength evaporation;and the evaporation accounts for 37% of the.daily runoff. The water quality of Daquan River belongs to weak alkaline slight saline water and hard water;pH is 7.3~8.1, the mineralization degree is 1500mg/L~2300mg/L, the total rigidity degree is 25 ~33H°, and the annual change of the water quality is not very obvious. However, from upper stream to downstream, the degree of mineralization and the total rigidity also the main ions contained increase gradually, thus the water quality becomes badly gradually, and all of this reflects the chemistry characteristics which are dominated by the evaporation and concentration.Based on the synthetic hydrological analysis, this paper educes that the annual runoff of Daquan River at the mountain pass is 240.9xl04m3/a;the water resources that can be used for irrigation in the Mogao Grottoes area is 85.51 xl04m3/a. Then points out that the water saving irrigation techniques should be extended and generalized widely, as well as the water sources should be opened up widely in Mogao Grottoes area, where water scarcity is because of resources, and then by building the water transfer projects designedly and step by step, to resolve the problem of water resources shortage thoroughly, and realize the sustainable utilization of water resources in the region.