Small islands are already regularly experiencing droughts and freshwater shortages  . Freshwater supply systems vary from household or small community systems such as rainwater harvesting systems and private wells to large public water supply systems using surface, groundwater and, in some cases, desalinated water . In many cases, communities rely on more than one water source, including a strong reliance on rainwater and groundwater . Groundwater resources in freshwater lenses  are essential in providing access to freshwater resources, especially during droughts when the collected rainwater is insufficient , leading to greater risks of water-borne diseases, with significant effects on nutrition , and improper sanitation poses additional risks to the limited groundwater resources . Drought events have also severely affected FWL recharge , with extraction rates further threatening available groundwater volumes . In conjunction with sea level rise, this poses serious risks to groundwater salinisation . In addition, FWLs are threatened by climate change due to changes in rainfall patterns, extended droughts and wash-over events caused by storm surges and sea level rise   . After small-scale wash over events, the FWLs have been shown to recover to pre-wash over salinity levels within a month .
IPCC
Climate Change 2022: Impacts, Adaptation and Vulnerability
IPCC Report