Numerical Simulation Of Groundwater System By Feflow In Zhangye Basin

Zhangye basin, located in the middle reaches of Heihe River with area of8941km2, is the key region controlling the evolution of water cycle within the basin area. From the view of hydrodynamics, based on the previous studies, GIS and Feflow were used as a platform to establish the numerical simulation model of groundwater flow according to the measured data about the aspects of hydrogeology, boreholes, meteorology and hydrology. After that, utilizing the observed groundwater level data to realize the suitable calibration and validation, we used the adjusted model to simulate the study area’s characteristics of groundwater flow and then predict the time-space dynamics rules. Some results are as follows:1. Based on the detailed and scientific analysis of the study area’s geological and hydrogeological conditions and the reasonable generalization of the aquifer system, the three-dimensional conceptual, mathematical as well as numerical model of groundwater system of Zhangye basin was successively constructed.2. Using the groundwater level data in2000to calibrate and validate the numerical model, after numerous attempts on the adjustment of the hydrogeological parameters and the source-sink data in some irrigation area, the three-dimensional numerical model was finally established which can describe the flow characteristics of groundwater during recharge and discharge.3. The simulated results for2000showed a very similar tendency in the flow field with the actual one, meanwhile, the simulated dynamic curves fit well with the actual one. Lower RMSE and higher R2values between water levels of simulated and observed indicated a satisfactory simulating result. The total recharge and discharge was9.62×10m3and11×10m respectively, and thus, the total balance was-1.38×108m3, the recharge of groundwater mainly came from the cannel and river seepage, while the discharge was caused by springs overflow and evapotranspiration. 4. Setting the groundwater level of January lth in2000as the initial condition, the calibrated Feflow model was applied to predict the groundwater level5years later under the two scenarios. The results indicated the increase, uncertainty and decrease levels from west to east of the basin, but growth along the Heihe river in general, it is mainly because of the additive effects as the exploitation from rivers and the groundwater. When considering the variation range of water level, the first scheme showed lower values than the second.