Study On The Groundwater Environment Evolution And Its Renewability In The South Edge Of Junggar Basin

The Junggar basin is one of the four inland basins. The Gu'erbanTonggute desert is laid in the middle, and the Aibihu lake is the lowest discharge zone. The plain, of north piedmont of the Tianshan mountains, which laid on the south edge of the Junggar basin, is one of the three development regions in Northwest of China. Because it is laid in the arid inland region, precipitation is rare, whereas evaporation is strong and eco-environment is very vulnerable, so groundwater is not only the key material base of society-economy development, but also the important composition of eco-environment, meanwhile, the information media of geology environment system. With influence of climate change and human activities, the groundwater cycle conditions have changed, groundwater environment has deteriorated, a lot of geological and eco-environmental problems have caused, such as groundwater dropdown hopper, groundwater containment, spring exhaustion, secondary salinization, vegetation degeneration and land dissertation so on. So researches on groundwater environment evolution and groundwater renewability with change of groundwater cycle conditions, is a key to solve regional sustenance development of society-economy and eco-environment improvement, meanwhile, a typical region of groundwater sustainable utilization to the similar northwest districts.Directed by groundwater system theory, embed in change of groundwater cycle conditions, enclosed by the main line of groundwater environment evolution and groundwater renewability, the paper, with the south edge of Junggar basin as typical regions, applied the basic theory of environment science, system science, and groundwater hydrology so on, reveals evolution process and development tendency on groundwater environment by analysis of natural and human factors affecting groundwater states combining qualitative means with quantitative method. Then, it discusses the basic theory and method of groundwater renewability on the basis of resource renewability theory. The research achievements are consisted of five parts as follow.The first achievement is about researches on formation conditions and cycle patterns of region groundwater cycle. During material, energy and information transformation between groundwater cycle system and its circular media, some conditions of groundwater recharge, discharge and runoff have changed, and then form five groundwater cycle patterns, which are many times cycle in an intermountain basin, many times cycle in a folded piedmont, many times cycle in an intermountain valley, many times exchanges in a sunken piedmont, one time exchange in a sunken piedmont. Circling with resource property, ecology and environment properties of groundwater, the thesis analyzes the relationship among these cycle patterns, groundwater environment evolution and groundwater renewability.The second achievement is about analysis on evolution process and driving force of groundwater environment. Firstly, with the main line of"states—driving force—response", from the view of change of groundwater states, with regime on buried depth of groundwater table, that on groundwater volume and groundwater quantity as environment factors, this paper analyzed groundwater environment evolution process and geological eco-environment effects. Secondly, from natural factors and human factors, by meanings of method such as grey relation analysis and main component analysis so on, it revealed driving force of groundwater environment evolution. And also it showed that climate change is the main influence factor in pediment plains, however, human activities is the main one in the clay plain zone.The third achievement is about evolution forecast on groundwater environment. With buried depth of groundwater table, groundwater volume, groundwater quality as groundwater environment factors, by a BP netWare model, a numerical simulation model, an index smooth model to forecast evolution tendency of groundwater dynamic field and its chemical field respectively. The research results showed that groundwater level may decline or rise in different hydrogeological units, whereas either groundwater mineralization or NO3- concentration raised.The forth achievement is about initial discussion on basic theories and method on groundwater renewability. Firstly, the paper put forward to a concept on groundwater renewability, that is, the total capability about groundwater recharge, regulation and storage, renewability and recovery. The concept has periodicity property, limitation property, compound property and so on. Among influence factors of groundwater renewability, which include not only natural factors such as hydro-meteorological conditions, recharge source conditions, groundwater cycle conditions etc., but also human factors such as groundwater development and utilization degree, human engineering construction activities etc.. Secondly, this paper established assessment index system of groundwater renewability, including natural recharge ratio, return recharge ratio, regulation and storage coefficient, balance ratio between recharge and exploration, groundwater residence time, transmissivity. Also it discussed relative assessment standards, Then by Analytic Hierarchy Process (AHP) weight method, based on assessment units of groundwater system; it assessed groundwater renewability by means of the comprehensive index model and comprehensive fuzzy model. Assessment results showed that groundwater renewability index was larger than 0.4 in intermountain zones and valley zones of the upper reaches of rivers, which means stronger renewability, that the index is smaller than 0.01 in the marginal zone of desert and oasis, which means weaker renewability, and that the index is from 0.1 to 0.2 in clay plains, which means medium renewability.The fifth achievement is about maintenance approaches of groundwater renewability and regulation control techniques. Firstly, choosing Manasi river watershed as a typical watershed, simulating combination regulation and storage of two kinds of groundwater reservoirs, the paper evaluated that the reservoir storage capacity was about 14.62×108m3 in intermountain zones and 6.01×108m3 in pediment plains,the total being up to 20.63×108m3, and that its renewability velocity was about 24.89a and 133.07a respectively. Secondly, with planning-construct Xishan urgent water source field as an example, in Wulabo low land of the upper reaches of Urimqin river valley, the paper simulated influence of construction on the water source field on Ganhezi finished water source field and its surrounding, discussed regulation and control patterns of well field for concentrated water supply. Finally, it put forward to synthetic measures to groundwater renewability, and consequently analyzed economic and social benefit by numeric stimulation of some schemes including regulation and storage, regulation and control, shifting water and saving water so on. All these can provide technique support to relieve contradiction between water resource shortage and water wastage, and to improve utilization efficiency of groundwater resources.