Spatial and temporal variation of groundwater recharge in shallow aquifer in the Thepkasattri of Phuket, Thailand

Whether groundwater resources can be sustainably utilized is largely determined and characterized by hydrogeological parameters. Estimating the groundwater recharge is one of the essential parameters for managing water resources and protecting water resources from contamination. This study researched the spatial and temporal variation of groundwater recharge in the Thepkasattri sub-district through integrating chloride mass balance (CMB) and water table fluctuation (WTF) methods. The chloride content of representative rainfall and groundwater samples was analyzed. Besides, WTF method was adopted from groundwater level data from 2012 to 2015. According to the CMB method, the mean recharge was estimated to be 1 172 mm per year, accounting for 47% of the annual rainfall. Moreover, the estimated recharge from the WTF method took 26% of annual rainfall in 2015. The recharge was underestimated according to the WTF method, because of the uncertainty in specific yield estimates and the number of representative wells in the study area. Moreover, the correlation between rainfall and water table fluctuation data indicated the positive linear relationship between two parameters. The spatial recharge prediction indicated that recharge was higher (1 200-1 400 mm/yr) in the eastern and western catchment, while that in the central floodplains was between 800 mm/yr and 1 100 mm/yr. In addition, low recharge value between 450 mm/yr and 800 mm/yr was observed in the south-west part of Thepkasattri. The spatial variation of recharge partly reflects the influences of land use and land cover of the study area.