Karst Aquifer GIS‐based model (KAGIS model) is developed and applied to Mela aquifer, a small karst aquifer located in a Mediterranean region (SE Spain). This model considers different variables, such as precipitation, land use, surface slope and lithology, and their geographical heterogeneity to calculate both, the run‐off coefficients and the fraction of precipitation which contributes to fill the soil water reservoir existing above the aquifer. Evapotranspiration uptakes deplete water, exclusively, from this soil water reservoir and aquifer recharge occurs when water in the soil reservoir exceeds the soil field capacity. The proposed model also obtains variations of the effective porosity in a vertical profile, an intrinsic consequence of the karstification processes. A new proposal from the Nash–Sutcliffe efficiency index, adapted to arid environments, is presented and employed to evaluate the model's ability to predict the water table oscillations. The uncertainty in the model parameters is determined by the Generalized Likelihood Uncertainty Estimation method. Afterwards, when KAGIS is calibrated, wavelet analysis is applied to the resulting data in order to evaluate the variability in the aquifer behaviour. Wavelet analysis reveals that the rapid hydrogeological response, typical of a wide variety of karst systems, is the prevailing feature of Mela aquifer. This study proves that KAGIS is a useful tool to quantify recharge and discharge rates of karst aquifers and can be effectively applied to develop a proper management of water resources in Mediterranean areas.
The province of Alicante is mainly occupied by rocks of carbonated nature. This implies that most of the provincial groundwater resources are located in aquifers of karstic nature. Due to the geological characteristics of the area, these aquifer systems show a wide variety of lithologies, rock ages and reservoir geometry (both in extension and thickness). In addition, these aquifers are distributed in a region with an important rainfall gradient between the north, with recorded average annual rainfall of about 900 mm, and the south, with averages of about only 300 mm. Thus, there is a strong contrast in terms of underground resources, more abundant towards the north of the province. In this study, two aquifers have been selected to stablish the influence of the climate regime and of karstic development on their recharge processes, and therefore in their resources. Both are of small dimensions, well monitored and have a similar hydrogeological behavior. The main objective has been to estimate the recharge in each of them and to evaluate to what extent climate and soil affects this variable. To achieve it, a soil water balance model, called RENATA, has been used. The two aquifers selected are the aquifer of Ventós-Castellar, located in one of the most arid areas of the province where average annual rainfall is around 300 mm, and the Mela aquifer, located in a more humid environment with an average annual rainfall around 600 mm.
For decades, the Province of Alicante, located in the Southeast of Spain, has experienced important economic development associated with groundwater exploitation. The scarcity of superficial resources and irregular distribution in the time and space of rainfall, typical of the Mediterranean environment, together with the extensive limestone outcrops, have made groundwater a key resource for the area. However, insufficient knowledge about aquifers, especially the lack of precise recharge estimates, hinders regional water management. This study establishes updated recharge estimates and water budgets for the 200 aquifers found in Alicante, using readily usable methodologies and available data. These are soil water budget models, groundwater flow models, water table fluctuation methods, and spring flow analyses. The results show low mean annual values of recharge from precipitation (69 mm/year and a coefficient of 12%) and two main differentiated domains. The first one, in the northeast of the province, under more humid climatic conditions with larger carbonate aquifer systems, has higher recharge coefficients, ranging from 14% to 24%, and greater resources. For the rest of the province, where aquifers are smaller and annual averages of rainfall range between 250 and 400 mm, average recharge rates are low (9–12%).
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