Sustainability of Costa Rica's water supply under climate change scenarios

Water scarcity and the difference between water supply and consumption is an increasing concern particularly under climatic uncertainty. Costa Rica has historically been at the forefront of environmental legislation; however, the water use framework in Costa Rica, still utilizes a quota style water allocation, which is problematic in extreme drought conditions. This allocation system paired with climate volatility makes it essential to quantify the future water demands compared to the water supply in Costa Rica. We use the Integrated Valuation of Ecosystem Services and Tradeoffs modeling system to quantify the water availability and usage in watersheds in Costa Rica under different climate and land cover change scenarios. We subsequently assess the spatial variability of water shortage and stress across Costa Rica. We find that there is a high spatial difference in water availability which do not match high use basins. In the highest demand areas, over 70 % of the water supply is projected to be consumed under a business-as-usual land cover change and high emission climate scenario. Low emission climate scenarios result in higher water availability, and increased forest regrowth increases water availability. Overall, the Guanacaste Province and the central valley which includes the capital city of San Jose are most at risk for experiencing high or moderate water shortage and stress in the future. Given the risks associated with water shortage and scarcity, it is important to address governance and stakeholder concerns as we move into the future.