The Upper Central Plain of Thailand commonly referred to as the country’s “rice bowl” has experienced a substantial decline in groundwater levels due to increased reliance on groundwater for irrigation, particularly during dry seasons when surface water availability is limited. In response, a conjunctive water management strategy has been implemented to optimize the use of both surface and groundwater resources. This study applied a calibrated MODFLOW groundwater model and the analytic hierarchy process (AHP) to evaluate sustainable groundwater extraction practices while accounting for surface water–groundwater (SW–GW) interactions. The model was calibrated using piezometric head data from 2008 to 2020, and groundwater abstraction was estimated based on irrigation demand not met by surface water, incorporating monthly rainfall trends and surface to groundwater use ratios. Sustainability was assessed across five provinces under three rainfall scenarios—low (1,400 mm)—using two drawdown thresholds: 24 m (approximately half the aquifer thickness) and 30 m (maximum well depth). AHP was used to prioritize four key criteria: transboundary flow, aquifer storage, river recharge, and rainfall recharge. Weights were derived from regression-based water budget analysis, and normalized scores were used to evaluate the relative influence of each factor. Under a 20 m drawdown constraint, sustainable groundwater extraction was estimated to range between 746 and 1,015 million m3 per year. The results underscore the importance of integrated water resource planning and provide a robust decision support framework to guide sustainable groundwater management in agriculturally intensive regions.
Koontanakulvong et al. (Tue,) studied this question.