Assessing climate changes impacts on tropical karst catchment: Implications on groundwater resource sustainability and management strategies

Developing tailored management strategies to ensure the sustainability of groundwater resource under climatic and demographic changes is critical for tropical karst catchment, where relatively small watershed and highly porous soil make this natural resource highly susceptible and thus very sensitive to those changes. In this study, long term impacts of climate variability on groundwater recharge and discharge at Oemau spring, Rote Island, Indonesia were selected and investigated. Following calibration and validation of groundwater model using MODFLOW code, groundwater flow was simulated for the period of 2020-2090 under HadCM3 global climate model (GCM) scenarios, using input data of weather variables downscaled by Statistical Downscaling Model (SDSM). The reported analysis suggests that the sustainability of groundwater resources, which was evaluated by assessing the ability of the spring to supply water demand from irrigation requirement and domestic consumption, generally varies over the period and will be adversely affected by climate change during dry periods when the area is projected to variably experience supply shortage of around 29-67 L/s as a result of 5.24-23.63% decrease of rainfall, 2.48-24.57% reduction of recharge, and 2.53-22.80% decrease of spring discharge, under HadCM3 GCM scenarios. A subsequent comprehensive set of management strategies as palliative and adaptive efforts was proposed to be implemented by relevant stakeholders to assist the community dealing with water deficit during the dry periods. Three main adaptive strategies, namely socio-cultural, technical, and ecological measures, were proposed by incorporating physical and socio-economic characteristics of the area. This study presents a blueprint for assessing groundwater sustainability under climate change scenarios and developing tailored management strategies to cope with adverse impacts of climate change, which may become fundamental guidelines across other karst islands in the future.