Research On Spatial And Temporal Variability Of Ground Water In Qitai Oasis

One of scarce resources in arid and semi-arid area is ground water resource; it is the lifeblood of plain oasis. With development of science and technology, human activity has an interference effect on groundwater circulation. Over-extraction of groundwater and unreasonably using water resource caused serious harm such as degradation of surface landscape,soil and groundwater salinization.(1) This paper discussed space-time dynamic change,spatial and temporal variability of ground water by Geostatistcal method, and analyzed main factors which influence spatial and temporal variability of ground water through spatial variation,temporal variation and correlation analysis. Then obtained conclusions as follow:From 1950 to 2005, the ground water presents remarkable variability. The ground water depth in plain oasis dropped rapidly, the main cause is rapid development of agriculture reinforced exploration intensity.(2) The coefficient of variation in Qitai Oasis in 1950 is 1.87 that belongs to strong variability. The coefficient of variation decreased with the time prolonged. The coefficient of variation in 2005 is 0.56; the variation of groundwater was rather weak. the semi-variogram is used to analyze spatial correlation of ground water, the result shows:Ground water in research area has high local correlation,the fluctuation change of spatially dependent range between 0.59km and 0.33km. the buried depth of ground water was affected by structural factors (such as climate,terrain,type of aquifer. etc) early and later by random factors(human activity such as farming system,irrigation methods,mining intensity etc.). Drawing kriging map and contour map of ground water by Ordinary Kriging method, the results show that ground water depth decreases gradually from north to south in the space and decreased rapidly in time domain. As a whole, buried depth of ground water in research area in continuous distribution. (3) The main factors affecting ground water buried depth are pumpage and fountain quantity. According to the correlation analysis, pumpage and buried depth manifested as strong positive correlation, correlation coefficient is 0.95; buried depth and Fountain Quantity manifested as strong negative correlation, correlation coefficient is–0.8. The agricultural irrigation in oasis depends on exploration of ground water, but groundwater Replenishment cannot be balanced the gap made by exploration. The buried depth linear decrease with increasing exploration. The spring water spill belt in Qitai oasis supply ground water in some extent, but volume of fountain decreased sharply. Till 2000, many fountain river vanished and some fountain wells dry rot.