Analysis On The Effect Of Hydro-engineering Development On Groundwater In Arid Area Based On Ecological Water Level

Northwest Arid Region scarce rainfall,strong evaporation,water resource shortage,ecological environment is fragile,the surface runoff is scarce and unevenly distributed and a series of characteristics of water resources,the groundwater becomes the basic condition for the formation of the ecological system in arid area oasis development and stability and the decisive factor is the key factor affecting the ecological environment.In order to alleviate the shortage of water resource in northwest arid region economic development,water conservancy project is bound to increase the development of water resources,after the operation of the project will affect the downstream groundwater flow and water resources,further impact on the local ecological environment,such a move will affect the body and cause damage to the local ecological environment is an urgent problem.The water source project of a complex water transfer project in inland arid region was taken as an example.FEFLOW software was used to establish numerical simulation model of groundwater flow in study area,in order to predict groundwater level changes and the impact groundwater sources in river valley after the project is going to completed.At the same time,based on the vegetation distribution map of remote sensing interpretation,to obtain the ecological water level distribution through the calculation of vegetation ecological water demand and ecological water consumption intensity.After comparison,the size and direction of different forest and grass from the ecological water level were obtained,and the regulation water quantity is calculated.The main research results are as follow:(1)Through the calculation of water balance,in the study area annual average amount of groundwater is-27.1×10~4m~3,showing weak negative balance and the scope of the whole basin water level reduce by 2.3cm.(2)Through groundwater simulation prediction result of different levels:After the project is going to completed,the annual average groundwater level reduction of study area is less than 0.35m.The width of the impaction beside the river is 1000m.The largest increase happens in April and the the largest decrease happens in May.The groundwater level of water source fluctuation is smaller.The construction of the water transfer project does limited impact on groundwater level in study area.(3)The different vegetation,such as forest,sparse forest,cultivated land,shrub land and desert land,Their suitable water level depth are sequentially increasing in different months.Consistent with the growth characteristics of vegetation.The maximum value of the suitable depth is 3.51 and the minimum value is 2.01.(4)After the project is going to completed.During the period of 6?9 months,the actual water level of shrub land,sparse forest,arable land and flood land is lower than their ecological water level,and the difference is 0.2?0.8 meters.The suitable area of forest and grass area was reduced,but the deficit area was increased.In general,the amplitude was not large,and the construction did not cause great damage to the ecological condition of the valley.57.1%of the study area develop groundwater deficit phenomenon and the total deficit is 302.76×10~4m~3.