Quantitative Techniques for Estimating Groundwater Recharge: A Review of Field-Based and Modelling Methods

Abstract

Groundwater recharge, the downward movement of water through soil to replenish aquifers is a critical process underpinning global freshwater availability. Accurate estimation of recharge rates is essential for sustainable groundwater management, particularly in regions facing water scarcity, over-extraction, and environmental degradation. This review synthesizes seven principal methods used to estimate groundwater recharge: lysimeters, the water balance method, groundwater table fluctuation (GTF) method, stable isotopes, chloride mass balance (CMB), drip tests in karst aquifers, and unsaturated zone modelling. Each method is evaluated based on its theoretical framework, field applicability, data requirements, accuracy, advantages, limitations, and representative case studies. Lysimeters offer precise, site-specific measurements but are costly and limited in spatial scope. The water balance method is scalable and widely used but sensitive to input data quality. The GTF method is cost-effective in unconfined aquifers but depends on reliable specific yield values. Isotopic and chloride tracers provide insight into recharge pathways and sources, particularly in arid and semi-arid zones, though they may be affected by anthropogenic inputs. Drip tests effectively characterize recharge dynamics in complex karst systems, while unsaturated zone models simulate recharge processes in detail under varying climatic and land-use conditions. The review emphasizes the applicability of these methods across various climatic and geological contexts, including arid, semi-arid, and humid regions. Research gaps, including scalability and data limitations, highlight the need for integrated approaches and advanced monitoring techniques. Comparative analysis suggests that no single method suffices across all contexts; instead, combining techniques tailored to specific hydrogeological and climatic settings yields more robust estimates. This review highlights the importance of method integration and site-specific considerations to improve recharge assessments, support informed water policy, and guide sustainable groundwater development.