Optimal pumpage to purify contaminative groundwater based on stochastic simulation
FU Xiao-gang1,2, TANG Zhong-hua1, LÜ Wen-bin3, WANG Xiao-ming2, YAN Bai-zhong2
1. School of Environmental Studies, China University of Geoscience, Wuhan 430074, China;
2. Key Laboratory of Sustained Development and Utilization of Water Resources, Hebei Province Collaborative Innovation Center for Sustainable Utilization of Water Resources and Optimization of Industrial Structure, Hebei GEO University, Shijiazhuang 050031, China;
3. Third Hydrogeological Engineering Team of Hebei Provincial Geological and Mining Burea, Hengshui 053000, China
Hydraulic capture technique is one of the most widely applied technologies to purify or constrain contaminants from further contaminated groundwater. Thus, how to determine the optimal pumpage is the key issue.The optimal pumpage calculated by commonly used deterministic methods were usually unreasonable. Therefore, the Monte Carlo method based on the stochastic theory, in consideration of the stochastic property of hydrologic-geologic parameters, was applied to investigate the effect of the spatial variation of hydraulic conductivity on the fate of hydraulic capture zone and a new method to estimate the optimal pumpage was suggested. It had been proved that when the 110m3/d determined by means of deterministic methods was adopted as optimal pumpage, the contaminated area lay exactly within the capture zone of the well, Then, stochastic method was used to investigate the effect of spatial variation of hydraulic conductivity on hydraulic capture zone and the results indicated that the capture zone did not always cover the entire contaminated area when the optimal pumpage adopted the same value (110m3/d) according to traditional deterministic methods, facing a convergent mean risk criterion as high as 24%. This study showed that the optimal pumpage concluded from the Monte Carlo method was more reliable than commonly used deterministic method, because it could takes such spatial variation of hydraulic conductivity into account to study how the spatial variability effected the hydraulic capture zone, that provided a stochastic method to estimate the optimal pumpage from the perspective of acceptable convergent mean risk criterion.
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