Determination of hydraulic conductivity and its spatial variability in the Jianghan Plain using a multi-format, multi-method approach

摘要

In recent times, the groundwater in Jianghan Plain, Central China has come under severe stress from agricultural and industrial demand. The spatial variability of hydraulic conductivity (K) in the region is important for better and sustainable groundwater exploration and management. In this study, we determined the spatial distribution of K using a multi-method approach, i.e. analytic and numerical simulation as well as intelligent optimization methods (particle swarm optimization (PSO) and differential evolution (DE)) and geostatistics. Data from 55 multi-format pumping tests situated across the middle-confined aquifer (consisting of late Pleistocene (Qp(3)s) and middle Pleistocene (Qp(2)j)) were used. Results showed that for transient pumping test with constant rate by multiwells, PSO and DE were faster and more precise, especially DE. For transient pumping test with variable rate as well as transient pumping test with constant rate by single well, the numerical method fitted the drawdown better, while the PSO and DE had large deviations at the early stage of pumping. Overall, the values of K vary from 0.032 to 10.64 m/d within Qp(3)s and 0.33 to 36.24 m/d within Qp(2)j. The spatial variability model demonstrated that the K values in Qp(3)s are greater than those in Qp(2)j. The heterogeneity elucidates the sedimentary development of the basin. These methods and results can provide new insights for estimating the spatial distribution of K for regional groundwater resources assessment in similar sedimentary environments around the world.