Characterization of hard rock volcanic aquifer system: Review of methods used for evaluating recharge and estimating hydraulic properties.

The complexity and heterogeneity of the volcanic aquifer's hydrogeological properties pose management challenges amid the global freshwater supply-demand imbalance. Rising demand from population growth, climate change, and socioeconomic activities has caused over-extraction, contamination, depletion, and threatens its sustainability. Effective management of these aquifers requires thorough characterization. Various methods have been applied to evaluate recharge and hydraulic properties in a volcanic aquifer. However, each method is limited by its underlying assumptions and application constraints, making the selection dependent on scale and heterogeneity of the aquifer. This paper is based on a systematic review of methods used to assess groundwater to evaluate recharge and hydraulic properties in volcanic aquifer systems. Each method was analyzed to assess its assumptions, limitations, and uncertainties in characterizing the volcanic aquifer. The results show that the estimated parameters vary across different volcanic settings, whether a single or multiple methods are used. The global variation is driven by differences in precipitation and aquifer complexity, while the local variation stems from preferential flow pathways that introduce uncertainty in estimated values. Researchers suggest using multiple methods and averaging to reduce uncertainty. This highlights the need for a sophisticated framework that accounts for the complexities of volcanic aquifers.