Study On The Influence Of The Development Of The Dry Area Reservoir Dam On The Regional Groundwater And The Forest And Grass Belt Along The River

Northwest arid area accounted for 22.4%of China's land area,it is an important way to The Belt and Road",occupies an important position in China's national development.Because of the climate drought,the scarce rainfall and the unequal distribution of water resources,the ecological environment in the northwest arid area is fragile,and the groundwater is the main factor determining the development direction of the oasis.The mutual transformation of groundwater and river water constitutes the basic way of the water circulation movement.The water supply of river water is the key component of the ecological water requirement of the river system.In order to alleviate the uneven distribution of water resources,dam projects were gradually built.But the construction and operation of the dam break the ecological environment stability under the natural conditions,which leads to the more fragile ecological environment in the surrounding and downstream areas of the dam project.In this study,the lower reaches of a dam project in the inland arid area are studied.Using the FEFLOW software,the numerical model of the groundwater flow is established in the study area,and the changes of the groundwater level before and after the project are built are simulated.The evaluation model of the influence of the reservoir dam development on the forest and grass belt in the lower reaches of the river valley was constructed by using the vegetation coverage,the vegetation coverage and the groundwater depth and the dive evaporation coefficient,and the influence of the dam project development on the groundwater level and the forest grass belt in the valley was quantitatively analyzed,and the groundwater environment in the study area was put forward.Suggestions for protection and dam project development.The specific research results are as follows:(1)The result of water amount equilibrium method shows that groundwater Multi-year equilibrium quantity is-316.642×10~4m~3 in the study area.It illustrates weak positive equilibrium.(2)The results of numerical simulation show that under the condition of P=50%after completion of the project,the groundwater level will vary by about 400m on the right bank of the river and about 500m on the left bank of the river.The groundwater level will vary by approximately-0.22m to-0.18m.After the completion of the project,under the condition of P=90%,the variation of groundwater level will be about 300m on the right bank of the river,about 600m on the left bank of the river,and the groundwater level will drop by-0.18 to-0.14m.According to the geological survey data,the forest and grass belt in the river valley is mainly concentrated in the depth of 1-3m of groundwater on both sides of the river bank.Therefore,the scope of the project after the project is designed is that the depth of groundwater level is 1-3m before the construction of the project.(3)Based on vegetation type,vegetation coverage,groundwater depth and evaporation,the assessment model for the impact of dam and dam construction on the downstream forest grass belt was constructed.The model was used to evaluate the ecological environment under the condition of P=50%before and after the completion of the project.The total area of poor and ecological environment is basically the same,but far exceeds the sum of good ecological environment,good ecological environment,and medium area of ecological environment;P=90%conditions are lower than the ecological environment before the completion of the project and ecological The area of poor environment has increased slightly,which is far more than the sum of the ecological environment,ecological environment,and ecological environment.To sum up,it shows that the forest and grassland in the river valley before the construction of the project is ecologically fragile.In general,the ecological environment changes with the change of the depth of groundwater.The area with poor ecological environment and poor ecological environment gradually increases with the decrease of groundwater level,and the ecological environment is good,the ecological environment is good,and the ecological environment is moderate.The decline in the groundwater level gradually becomes smaller.