The Seepage Calculation And Surrounding Salinization Predication Of Plain Reservoir In Arid Area

Construction of plain reservoirs in the arid area can effectively alleviate regional water shortages, butreservoir leakage is more serious than the mountains area due to the long dam line, which may leads toraising downstream groundwater levels, groundwater in this area has become a sensitive factor affectingland ecological environment. Taking a large plain reservoir which is located in Xinjiang as the researchobject, for potential soil salinization and desertification currently existing problems, this paper calculate theeffect reservoir seepage on downstream groundwater depth by using ABAQUS simulation software,explore the ecological groundwater table around the reservoir and estimate the water demand to restore thedesert land. Preliminary results are as follows:(1) The timing seepage performance of reservoir actual operating conditions which based on a simulationof the typical cross-section by using ABAQUS software, shows that: The water level on495m, the seepageis relatively slow so that forecasting the impact of reservoir started running downstream groundwaterreservoir leakage after75years to reach the limit. The groundwater depth, which is200m far from the damtoe, has increased from the initial10.48m to1.45m, while the depth400m far from the dam toe hasincreased from the initial10.6m to2.15m. The seepage are faster than the previous conditions, upstreamwater level is500m under the most adverse circumstances, predicted that the impact would reach a steadystate when the reservoir run to40years, when the depth of the200m observation points rise up from aninitial10.48m to1.25m, while the400m points rise up from an initial10.60m to1.95m, and followed byslight fluctuations.(2)The threshold depth of groundwater is a standard determine whether there will be soil salinization. Itis analyzed that the threshold depth of groundwater applies to all downstream region is2.85m.(3) The timing groundwater depth data of a typical cross-section, compared to the threshold depth ofgroundwater, can predict the salinization possibility in reservoir downstream, the results showed that:1) Inreality, during the reservoir storage, the location of the threshold depth keep moving to the farther distance.,75years later stabilized, then the farthest range of soil salinization in2095will reach to609m from the toeof the dam;2) the most unfavorable case is the groundwater levels rise quickly so that the seepage velocityget high, to2045when it reaches steady state.(4) A typical cross-section at different time points calculated groundwater depth analysis can be drawnfrom the range of reservoir leakage recharge area, the results showed that: the upstream water level1)When the water level upstream of the reservoir is495m, the boundary of reservoir leakage recharge movesfrom the initial position300m from the toe of the dam to the dam downstream direction, Until75yearsafter impoundment,in2082, the boundary of reservoir leakage recharge stabilized,the farthest boundary ofreservoir leakage recharge will appear in2105, located at3190m from the toe of the dam;2) upstreamwater level is500m under the most adverse circumstances,the boundary of reservoir leakage rechargemoves from the initial position300m from the toe of the dam to the dam downstream direction, Until40years after impoundment,in2045, the boundary of reservoir leakage recharge stabilized.(5) Campared with the result before the reconstruction of the QiaLa reservoir, the author thinks that theeffect is obvious. Especially in improving the impermeable system and reducing the range of salination.