Study On Water Balance Model Of Irrigation Area In The Middle Reaches Of Heihe Basin

Heihe river is the second biggist endorheic river in our country. Recent years, as a result of unreasonable, excessive development in the irrigation district of the middle reaches of Heihe basin , the terminal lakes in the basin vanished, multitudinous natural channels abandoned and became the oasis's interior source of sand, the natural oasis withered, and the land desertification is developing rapidly. Therefore, it has an important research significance for the water resources planning of the basin, the water resources optimal operation and utilization , the protection of sustainable and reasonable development of agriculture in the ecological environment river basin to study the diffusion ways of the water of Heihe river in the irrigation area of middle reaches ,and to analysis the ways of consumption of water volume in various systems of the irrigation area in a quantitative way. In view of the irrigation district in the middle reaches of Heihe basin, this article has conducted research on following several aspects on the foundation of analyzing the domestic and foreign SPAC system theory and the present situation of water balance model study in the irrigation area.(1) In this article, the current domestic and foreign research technique and research results on the SPAC system and the water balance model of irrigation area were analyzed. Taking the irrigation area in middle reaches of Heihe basin as the application background, closely unifying with the actual situation of the research area, taking the conceptive hydrology model as the foundation, and taking the SPAC theory and the water balance theory as the rationale, the water balance model of the irrigation area which unified the dynamics mechanism, the water supply system of the irrigation area, the drainage system and the reservoir system together has been established . In the field criterion , taking the field holard as a center, the model has considered the exchange and transformation of the moisture content between different mediums;in the criterion of irrigation area, the factors of the management of the irrigation area such as the irrigation system, drainage system, land utilization, plant society, and the ways of water supply of the irrigation area and so on have been considered .(2) In this research, the water balance model of the irrigation area had considered with emphasis the computation modules of the evaporation loss of the reservoirs and the canal system. In the study of model on the criterion of irrigation area, the predecessors seldom considered the evaporation loss quantities of the reservoirs and the canal system. Taking the advantages of the natural marsh land, the plain reservoirs in the middle reaches of Heihe basin were constructed. Generally, the gathers the water depth of the reservoirs is low , the evaporates and the leakage loses of the reservoirs is very big. Except the evaporation losses of the water surface of the reservoirs, the quantity of the canal system's evaporation loss cannot be neglected in the water balance computation of the irrigation area.(3) In this article, the characters of the SWAP software in application were introduced in detail, the boundary conditions of the SWAP model were determined, and the SWAP software was used to simulate the water balance of the farmland system in the irrigation area.(4) The established water balance model of the irrigation area has been applied to the Yingke irrigation area in the middle reaches of Heihe basin, and the quantitative analysis of water consumption situation of Yingke irrigation area in 2004 was carried. At the same time, on the foundation of the water balance computation in the Yingke irrigation area, the water consumption of three counties in the middle reaches of Heihe basin was computed. The computed result is reasonable, and can be applied as a reference to the policy-maker.