Research On Comprehensive Governance Of Groundwater Over-Exploitation Area Of Oasis City In Arid

For series of ecological environment problems caused by groundwater exploitation in Korla City,the townships and towns of Korla City as the research object,we used mathematical statistics and other methods to evaluate the groundwater resources.The water level dynamics method,exploitation coefficient method and environmental impact factor method were used to divide the groundwater over-exploitation area.At the same time,from the perspective of water volume and water level,the comprehensive governance measures for the over-exploitation area were formulated.The assessment system of comprehensive governance measures of groundwater over-exploitation area was constructed by analytic hierarchy process(AHP),and in order to verify the governance measures,the prediction models such as grey model GM(1,1),Holt-winters and NAR neural network of time-series were used to predict groundwater dynamics of the typical monitoring in the study area.The main conclusions were got as follows:(1)By 2015,the total amount of groundwater resources was 331.3 million m3/a,and the exploitable amount of groundwater was 215.85 million m3.The actual amount of groundwater exploitation was 514.99 million m3.The groundwater dynamic level of the monitoring well fluctuated during the year(2000,2010 and 2015),and the dynamic curve characterized was exploitation type.From 2000 to 2015,the inter-annual groundwater dynamic level showed a general downward trend with fast and medium-speed.Groundwater exploitation was the main driving force which affects the change of groundwater depth.(2)The total area of the over-exploitation in Korla City was 982.81 km2,in which the general over-exploitation was 195.97 km2,and the serious over-exploitation was 786.84 km2,which belonged to the medium-sized over-exploitation area.The comprehensive governance measures for over-exploitation area include engineering measures(land withdrawal and water reduction,well sealed fill,water source replacement and efficient saving water)and non-engineering measures(water resource management,water price reform and groundwater dynamic monitoring).(3)Comparing between before and after governance of groundwater over-exploitation area,according to 12 water quality monitoring wells,there were three wells with better water quality,six wells had the same water quality,and the water quality deteriorated in three wells.The total over-exploitation area was reduced 395.08 km2,which accounting for 81.8%of the area which should be governed(482.81 km2)before 2020.(4)The score of the comprehensive governance evaluation system of the over-exploitation area in Korla City was 60.02,which indicated that the comprehensive governance measures were reasonable and the comprehensive governance effect basically met the requirements.In prediction model,the average relative error of NAR neural network model was small,which was suitable for groundwater level dynamic prediction in the study area.By the end of 2020,the groundwater level of groundwater monitoring wells(J4 and J12)were 18.0 m,and 26.1 m respectively,which met the groundwater level governance standard.