Abstract
Understanding the recharge mechanisms in the vadose zone is crucial to groundwater management and artificial recharge development. In this study, a systematic characterization of seasonal groundwater recharge was done using time-lapse electrical resistivity tomography (time-lapse ERT). The objective of this study was to characterize the seasonal groundwater recharge through the vadose zone and streams. A total of six electrical resistivity surveys in two locations were taken during the dry and rainy seasons using an advanced geosciences incorporated (AGI) SuperSting R2 resistivity meter in 2018. Then, time-lapse inversion was calculated using the dry season ERT as the base model and the rainy season ERTs as the monitoring datasets. The results showed a significant decrease in inverted resistivity from the dry season to the rainy season, which suggests rainwater infiltration through the vadose zone. Similarly, significant water level rise was observed in wells monitored during the survey indicating groundwater recharge. The time-lapse ERT showed, in one case, the Nang Dak stream and the unsaturated zones are the preferential groundwater recharge zones throughout the year; in another case, the Rieng stream is the groundwater discharge zone and the vadose zone is the preferential recharge zone. Finally, a simplified conceptual hydrogeological model representing the study area is presented to visualize the recharge mechanisms in the study area.
Highlights
Groundwater is the main source of fresh water all over the world and accounts for 30% of all freshwater bodies [1]
Any water infiltration attributed to the subsurface passes through the vadose zone before it reaches the water table [3]
Our objective was to characterize seasonal groundwater recharge variation in the vadose zone consisting of alluvium and weathered/fractured granite, and to evaluate the roles of the nearby streams in groundwater recharge
Summary
Groundwater is the main source of fresh water all over the world and accounts for 30% of all freshwater bodies [1]. To meet the increasing demand for fresh water, groundwater needs to be replenished. Groundwater recharge is a hydrogeological phenomenon where water from rainfall, lakes, snow melts, or streams moves downward to an aquifer and is stored as groundwater. There are two types of groundwater recharge: diffuse and focused. Diffuse recharge comes from widely distributed sources, for example a rainfall, while focused recharge comes from localized sources, for example lakes, streams, or depressions [2]. The vadose zone is the soil layer that separates the ground surface from the water saturated zone. Any water infiltration attributed to the subsurface passes through the vadose zone before it reaches the water table (saturated zone) [3]. Understanding the recharge mechanisms in the vadose zone is crucial for developing and protecting groundwater resources
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