Study On The Influence Of The Storage Of Qu Jiang Lake On The Groundwater Dynamic Field In Xi'an

The urban artificial lake project effectively improved the urban ecological environment effect and the quality of the city.Artificial lake profoundly affected the change of urban hydrological circulation system,triggering a series of trouble of water resources,water environment and geological environment.In order to reveal the influence of the construction of artificial lake on the groundwater and the water environment in Xi'an city,the paper studied the artificial lake of QuJiang.The paper had reviewed the literature,collected data,investigated field and made the experiments indoor and outdoor.Based on the analytical method,water balance method,gray relational analysis method and numerical simulation method,the groundwater dynamic field of QuJiang lake was studied from the driving factors of groundwater dynamic field and the leakage.The main conclusions were as follows:1.Compared with the non-built lake,the change of the groundwater level in the surrounding area was obvious after the impoundment of the QuJiang Lake.Before the lake was built,the groundwater level near the QuJiang lake was showing a downward trend.The average level of decline in groundwater level was only 0.07m/a.The annual variation of groundwater level is as follows: the groundwater level continued to decline from the January to September,and gradually increased after October.After the lake was built,groundwater level showed a slow upward trend from the year of 2009 to 2010.The groundwater level showed slowly rising from January to October.Form November to January the water level gradually decreased,the increase rate of 0.31 m.2.There was obvious hydraulic connection between the QuJiang lake and the groundwater.The bottom of the seepage project appeared a super-design leakage phenomenon..The hydraulic gradient of the rockfill dam in QuJiang was obviously larger than the hydraulic gradient on the north and south sides.The elevation of the water level affects the form of the dive.The total flow of lake ditch was 1.549 million m3,the average daily flow was 1033m3/d,the maximum flow during the observation period was 1500m3/d.3.The driving factors of groundwater were obviously different in different areas around QuJiang Lake.The average change in the level of water in the middle of the lake or near the shore was near 0.21 m,and the average change in groundwater level at the south of lake was 0.75 m.4.The main driving factors of the groundwater level near the south of QuJiang lake are lateral runoff and lake water level by means of gray relational analysis;The main driving factors of the groundwater level in the northern area are the leakage amount;the main driving force of the groundwater level in the central part of the lake are rainfall and evaporation.5.The analytic method was used to study the leakage under different impervious conditions.The permeability of composite geomembrane was 71m3/d when the composite geomembrane was used as the weakly permeable layer at the bottom of QuJiang Lake.When the composite geomembrane was strong permeable,the leakage was 228m3/d.When the bottom of the lake was only the original soil compaction seepage,the leakagewas 988m3/d;when QuJiang lake does not take any measures to prevent seepage,the leakage was 25863m3/d.6.Through the hydrological and meteorological monitoring data,the water balance method was used to study the leakage of lake bottom.The daily leakage of the lake was 4608 ~ 5027m3/d.The daily leakage of Qujiang Lake was 4429 ~ 5281m3 / d when no rainfall or no artificial recharge was used.Using the monthly equilibrium method,the leakage of Qujiang Lake was 1951 ~ 7228m3/d.7.Visual ModFlow was used to simulate the change of groundwater steady flow field under different leakage conditions.The simulation results show that the water level of the QuJiang lake was obviously lifted in the case of damage to the bottom of the lake.Compared with the natural flow field,the average rise in the water level of the section was 2.07 m,1.52 m and 0.90 m,in the case of complete destruction,destruction of 30% and destruction of 10%.Under the condition of 10% damage of the impervious layer,the groundwater level rises as a whole,and the hydraulic gradient increases in the direction of the runoff of the groundwater.When the bottom of the lake was completely damaged,the water level was raised by about 2m.In the case of complete destruction of the seepage layer at the ground fissure,the flow field of the lake in the south of Qujiang changed little,and only the water level in the northern part of the lake appeared uplift.