Abstract
Groundwater recharge remains almost totally unknown across the Mekong River Basin, hindering the evaluation of groundwater potential for irrigation. A regional regression model was developed to map groundwater recharge across the Lower Mekong Basin where agricultural water demand is increasing, especially during the dry season. The model was calibrated with baseflow computed with the local-minimum flow separation method applied to streamflow recorded in 65 unregulated sub-catchments since 1951. Our results, in agreement with previous local studies, indicate that spatial variations in groundwater recharge are predominantly controlled by the climate (rainfall and evapotranspiration) while aquifer characteristics seem to play a secondary role at this regional scale. While this analysis suggests large scope for expanding agricultural groundwater use, the map derived from this study provides a simple way to assess the limits of groundwater-fed irrigation development. Further data measurements to capture local variations in hydrogeology will be required to refine the evaluation of recharge rates to support practical implementations.
Highlights
Groundwater is a primary resource for agricultural, domestic and industrial uses globally [1].it remains largely underutilized in the Mekong Basin [2] and in parts of Laos and Cambodia where the primary source for irrigation is surface water [3,4]
The4.1.median of specific annual baseflow computed in each catchment with the local
Like many other studies under temperate or tropical climates [46,47,48], ourare results indicate that spatial variations in baseflow, used as a proxy of groundwater recharge, are predominantly controlled by rainfall and ET0
Summary
Groundwater is a primary resource for agricultural, domestic and industrial uses globally [1]. It remains largely underutilized in the Mekong Basin [2] and in parts of Laos and Cambodia where the primary source for irrigation is surface water [3,4]. Groundwater resources are better protected from pollution than surface water, and allow for more reliable abstraction over time due to smoother inter-annual and inter-seasonal variations than the surface water strongly influenced by the monsoonal climate [5]. Total utilizable groundwater volume in an aquifer is controlled largely by the seasonal variations in groundwater recharge, the drainage from and into rivers, and pumping. Groundwater recharge occurs either in diffuse form (from rainfall infiltration via the unsaturated soil zone), or more locally via water seepage through riverbeds and other water bodies such as lakes
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