Unit Network Model Of The Environment, Water Resources Systems Analysis Study

With the development of human society, human activities influence water circulation of basins more and more drastically. In many districts where human activities are very intensive, the influence of human activities to water circulation even exceeds the one of natural process. However, this kind of trend will further continue, even be intensified. At present, the water resources shortage and water environment degradation existing in many basins of China intensively reflect this phenomena and trends. The water resources system of basin is the complex system of human and natural water circulation, and dual complex character becomes the intrinsic property of water circulation. It is the most important water science condition that dual and complex character is more and more outstanding at present. This article discusses the water circulation status of different stage under the common action of natural process and human activities, and studies the key factors of human activities and their action regulation.Based on the reality and character of water circulation, the unit network model reasonably generalizes the water circulation factors of the complex system composed of society, economy and water resources, divides the whole basin into several areas according to basin's natural geography and social economy. At the meantime, it generalizes the water circulation into natural and human water circulation system using water supply and water consumption unit to simulate their structure factors. Water supply units include reservoirs, river channels and ground water, and water consumption unit include cities (domestic and industrial water utilization), agricultural irrigation, eco-environment and so on. At first, it analyzes the water circulation characters and their operation law of units, then according to the relation among units it links units into unit network to build the unit network model. This model not only describes water interchange relation of volume, but also studies the diffuse and transmission of contaminants, and uses water quality model to simulate the water environment status of reservoirs and channels.Taken Taizi river basin for example, the conclusions of this article are as follows:(1) In 1976, the water circulation of Taizi river basin is sound, however the status of 1995, 2002 and 2010 is not sound. (2) The draw ratio of ground water, guarantee ratio of industrial and agricultural water are the key factors of human activities which influence water circulation of Taizi river basin. But the influence range and degree of every factor is different. Industrialwater has much influence on cities water supply and surface water environment status, but has little influence on agricultural water supply. Although agricultural water consumption takes very big rate in water consumption structure, it only has much influence on the improvement of the guarantee rate of agricultural irrigation. The reason of this kind of phenomena depends on the almost separation of water sources of cities and agricultural water supply. (3) Under the pattern of sound water circulation, the ratio between total water supply and total water resources generally can't exceed 50 percent, the production structure is based on water environment carrying capacity of basins.(4) Both the change of basin's underlying surface and the increase of water resources utilization degrade the status of water circulation, but the latter plays the dominant role in the influence to water circulation. The results and conclusion of this article show that it is feasible to study the mechanism of water circulation of basin using unit network model.