Evaluating Aquifer Recharge in Volcanic Islands: A Case Study of Maspalomas, Gran Canaria

In recent decades, the need to quantify and understand water resources in drylands, such as insular volcanic systems, has grown, along with the obligation to assess how climate change might impact them in the future. These resources are constrained not only by climatic, geographic, and geological factors, but also by increasing demand from agronomic, urban, and tourism areas. This, is mostly relevant in the Canary Islands, especially in the coastal region of Maspalomas located in the southern part of Gran Canaria, where an exponential increase in freshwater demand has been observed from 1960 to the present.

Within the framework of the NATALIE project a hydrological model was developed using the Soil and Water Assessment Tool (SWAT) software to estimate the infiltration and recharge rate of Maspalomas aquifers. The water balance results show an average annual precipitation of 272 mm, of which 68% evapotranspires (181 mm/yr). The infiltration rate is estimated at 19% of the precipitation (50.65 mm/yr), equivalent to an annual aquifer recharge of 8.2 hm³.

Gran Canaria faces a unique challenge in water resource management due to strong anthropogenic pressure and the impact of climate change on reserves and available resources. Climate projections towards 2100 suggest a drop of 22.2% in annual precipitation, which would represent a reduction of 34.63 mm/yr in infiltration, i.e., a decrease of 2.59 hm³/yr in groundwater reserves. These results will be key to both prevent scarcity and improve fresh water resource management in volcanic islands.

Keywords: Water resources, Maspalomas, SWAT, recharge rate, climate projection