Hydrological model and integrated GIS techniques for simulation and analysis of the long-term water balance in a coastal aquifer, Spain

Abstract

Understanding the water balance of a region as accurately as possible is essential for the optimal and sustainable management of water resources. In this study, a hydrological model, WetSpass-M, was used to simulate the spatial and temporal distribution of water balance components such as the groundwater recharge, surface runoff, and actual evapotranspiration in the Motril-Salobreña coastal aquifer (south of Spain) for the period 1980–2020. To estimate the water balance components, data on the land use/cover, topography, slope, soil texture, irrigation allocation, and groundwater depth were combined with meteorological data (precipitation, temperature, wind speed, and evapotranspiration). The sensitivity analysis findings showed that the model results were affected by the global and local parameters, specifically intensity coefficient, land and soil factors. In addition, an agreement was observed between the simulated recharge values and those calculated using the WTF method, with a correlation coefficient (R2) of approximately 86%, a mean error (ME) of 1.1 mm/ month, and a mean absolute error (MAE) of 2.5 mm/month. The model simulation results for water balance components in the study area showed that of the total amount of water which enters into the system (863 mm/year), only 19% reaches the aquifer as recharge, which represents an annual average of approximately 164 mm. Of the remainder, 28% is surface runoff, and 53% is lost through actual evapotranspiration. Therefore, approximately 7.2 Mm3 of water per year is recharged into the MotrilSalobreña coastal aquifer. The integration of the WetSpass model with GIS has shown its effectiveness as a powerful approach for assessing water balance components. The model findings have also allowed implementation of a regional groundwater model for the study area, which can be used to simulate different aquifer management scenarios. Finally, the present study provides baseline information for policymakers and stakeholders involved in the management and development of water resources in the study area.