Climate vulnerability studies on the three most important river basins in Costa Rica – the Reventazón, Térraba, and Grande de Tárcoles - show alarming trends in runoff rates and alterations in the hydrological cycle. Alterations in the water cycle could affect water runoff, erosion, and sedimentation, thus causing severe flood-related problems. Impacts would also be reflected in the exploitation of water resources to generate hydroelectricity and supply irrigation systems, aqueducts, and sewer systems. Even though water availability is not a problem at present, the population’s needs for reliable and clean water supply are not fully met due to a lack of integrated water management policies. The issue of access to quality potable water is more critical among the highest-risk populations of the country and future climate-induced flooding events will only exacerbate it. For example, in the Central Valley of Costa Rica, an imbalance in the potable water supply is expected by 2022, due to a combination of the effects of climate change and an expected population growth of 1.1 million people. Further concerns exist under expected future severe dry conditions, as inappropriate agricultural practices, deforestation, soil erosion, and the excessive use of agro-chemicals may deteriorate surface and groundwater quantity and quality in rural areas and around the San Jose metropolitan area.
This section provides insights into projected climate change impacts on various hydrological indicators.