GIRAgua recharge: Pilot project aquifer recharge in the Elqui basin in the Coquimbo region, Chile Short general project overviewBecause of climate change, water scarcity and security are a growing challenges in Chile. In coastal zones, such as Coquimbo-La Serena conurbation, the fresh water availability is an increasing challenge, with changes in water demands that increase water scarcity. Climate change strongly affects the water availability, especially in the northern half of the country.The water supply is mainly managed and distributed with surface water; however, due to shortage in surface water supply the groundwater is increasingly used and therefor depleting. The water availability of surface water is used for the agricultural sector (80%), industry (10%) and the urban area (10%). During the ‘off season’ period surface water could be used to recharge the groundwater resources. This combination of surface and groundwater management is not done at this scale. Other water resources, like waste water treatment plants effluent from industry and town of La Serena and Coquimbo, to replenish the water storage underground in quantity and quality can also be used to obtain a more comprehensive water management system.The present volume of the reservoir Puclaro (200 million m3) can be extended with two subsurface storage reservoirs (aquifers) Elqui Bajo (140 million m3) and Pan de Azúcar (170 million m3). These volumes will give sufficient volume of water for a more sustainable development in the Coquimbo region. The subsurface storage areas need to be recharged because of earlier depletion and that is the main objective of this pilot. The construction of the pilot system involves several alternatives and/or combinations of measures for subsurface water storage, such as, infiltration wells, infiltration ponds and water treatment systems. The aquifer can be infiltrated but the question is with which speed and to which expected volume. This needs to be tested.After having more tangible information on the actual test case we will work on a cost-benefit analysis of the integrated system and possible externalities through a financial business case for a full scale implementation in the region, which in turn can be used in other regions. The involvement of the stakeholders stretches their existing mandates, roles, permitting and application of regulations within the existing regulatory framework; advising, adaptation, with bottom-up initiatives form part of this project.The results of the project will be used to apply it on a larger scale in the Elqui River Basin and furthermore to other regions in Chile. For that reason a peer group of organizations of other river basins (Copiapó, Aconcagua, Temuco) will be formed to learn from the findings in this pilot project and who will facilitate an easier acceptance and application in other regions.Initial activities and results of the projectThe main activities are:- Understanding of the groundwater system through geophysics and a groundwater monitoring network.- Infiltration of the water into the aquifer; design, implementation and monitoring of an infiltration pilot system.- Extraction of the water in times of deficit; measurements.- Building a business case of the aquifer recharge.What makes the technology, product, method or approach used innovativeCoastal Aquifer Storage and Recovery (COASTAR) is a Dutch innovative concept developed by Arcadis, KWAR and Deltares and aims for the use of subsurface solutions for a robust water supply and drought control by closing the water gap between water supply and demand in space and time.