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<p>Remote sensing is recognized as the most feasible means to provide regional information on land surfaces and monitor soil parameters such as soil moisture and evapotranspiration. The use of satellite-derived products can be crucial for groundwater resources in karst aquifers, particularly in regions, such as southern Italy, where groundwater availability drives economic and social development and there is a lack of monitored data. This study aims to expand the classical hydrogeological approach, used for the estimation of groundwater recharge of karst aquifers, to the understanding of the hydrological role of soil coverings by the integration of field monitoring and products derived by remotely sensed data. The research was conducted on the representative Mts. Soprano-Vesole-Chianello karst aquifer (Campania, southern Italy). Copernicus Global Land Services Soil Water Index (SWI) and Moderate Resolution Imaging Spectroradiometer (MODIS) Evapotranspiration products were explored to assess soil water content and evapotranspiration regimes. The analysis included time series gathered by a monitoring network consisting of 5 soil moisture multi-profile probes, working since 2021. The SWI1km provides daily soil water content information at 1 km resolution. Depending on the uncertain calculation, not considering evapotranspiration and soil texture, the SWI1km product provides 8-SWI estimations and the related quality factor values. Instead, the MOD16A2 is based on MODIS data and provides 8-day evapotranspiration estimation at 0.5 km resolution. The product collection is based on the logic of the Penman-Monteith equation, which integrates inputs of daily meteorological re-analysis data along with products derived by (MODIS) including vegetation property dynamics, albedo, and land cover.</p><p>Both products showed zones of no-data occurring across the mountain areas of the karst aquifers. This limitation is related to the algorithms that consider several parameters such as topography (slope aspect and angle) and occurrence of clouds for product generation.</p><p>The primary outcome of this study was the extraction of SWI values and the calculation of a mean value for the 8-SWI values, weighted by the related quality factor (<em>SWI<sub>w</sub></em>). <em>SWI<sub>w</sub></em> showed a constant difference of about -20% in comparison to the daily average values obtained by field monitoring. Despite this discrepancy, the annual trend of the <em>SWI<sub>w</sub></em> was found being very consistent with the soil moisture probe measurements (corr. > 0.68) and displaying a good response to rainfall events.</p><p>Moreover, the MODIS <em>ET</em> data displayed the expected pattern of evapotranspiration with a temporal resolution not achievable in other ways considering the lack of local meteorological data.</p><p>In order to cope with missing data across the mountain areas of the karst aquifer, a spatial interpolation of <em>SWI<sub>w</sub></em> and MODIS <em>ET</em> was carried out by different geostatistical techniques.</p><p>The findings suggest that SWI1km and MODIS16A2 are useful in monitoring soil water content and evapotranspiration of soils covering karst aquifers and controlling groundwater recharge. Although there are limitations due to missing data, both products can be still effectively utilized if properly interpolated. Therefore, they can be considered fundamental for assessing patterns of groundwater recharge in karst aquifers, especially in areas which are not extensively monitored as in the case of southern Italy.</p>

The analysis of groundwater resources is a particularly significant aspect of the economic, social and environmental development of the national territory. This is particularly relevant for the Campania region which, although characterized by the most significant aquifer systems of southern Italy, suffers from critical issues related to the progressive increase in demand and climatic variability at different time scales. In this framework, the lack of data concerning the survey of springs, including the minor ones, and of historical discharge measurements represents the main limitation to a more comprehensive regional hydrogeological characterization. The only source of historical data regarding the systematic and comprehensive survey of springs and discharge measurement is the Publication No. 14 of the National Hydrographic Service of the Ministry of Public Works “The Italian springs. List and description” reporting measures made between the 1920s and 1940s which was published in distinct volumes for each compartment. Despite its potential relevance, this source has so far been little used in regional hydrogeological studies. In this paper, a comparative analysis among data of springs derived from the Publication No. 14 and from measurement campaigns made by the Cassa per il Mezzogiorno (Special Project 26), between the 1960s and 1980s for main springs, was carried out for the Campania region. The information available from each source was validated through a cross-check, by means of a comparison of coordinates and a statistical analysis of the characterizing parameters. The new dataset allowed to expand the hydrogeological regional characterization with a higher number of springs, including the minor ones. The results obtained recognize the Publication No. 14 of the National Hydrographic Service as an important source of data to not be overlooked, especially in a condition of historical data shortage, by which can be both carried out regional hydrogeological and temporal analyses as well as identified integrative groundwater resources.

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Abstract. Nowadays the phenomenon of Global Warming is unequivocal, as confirmed by the latest reports of the IPCC and studies of the climate-change impacts on ecosystems, global economy, and populations. Among these analyses the effect of climate change on groundwater is a very relevant task especially for regions whose economic and social development depends chiefly on groundwater availability, as for the southern Italy. In such a territorial framework, this research was focused on analyzing: i) comparison of precipitation and air temperature obtained by Regional Climate Models (RCMs) and meteorological time series recorded in a part (1950–1996) of the “historical experiment” period (1950–2005); ii) effects of climate change on scenarios of air temperature (T) and precipitation (P) and, consequently, on scenarios of actual evapotranspiration (ETR) and effective precipitation Pe (P – ETR). The latter was considered as a proxy of groundwater recharge of the principal aquifer systems of the region, represented chiefly by the karst aquifers. To achieve a detailed hydro-climatological characterization, an Ensemble of 15 RCMs (E15) derived from the European Coordinated Regional Downscaling Experiment (EURO-CORDEX), at a spatial resolution of 0.11° (~12 km), was analyzed. Specifically, two IPCC Representative Concentration Pathways of greenhouse gases (RCP4.5 and RCP8.5) were considered. The E15 was calibrated in the validation period (1950–1996) by a statistical comparison with data observed by the regional meteorological network managed by the former National Hydrological Service (SIMN), Department of Naples, which was active in the period 1921–1999. As a principal result, the E15 was found with a statistical structure very similar to those of observed annual precipitation (OBSP) and mean annual air temperature (OBST), characterized by a very similar frequency distribution. Accordingly, an inferential statistical approach was performed for calibrating E15 precipitation (E15P) and air temperature (E15T) based on the compensation of the difference with OBSP (+7 %) and OBST (-16 %). The E15 projects a reduction in precipitation and an increase in air temperature under both RCPs, with a divergence point between the two scenarios occurring by about 2040. As a principal result, Pe shows declining trends for both RCP scenarios, reaching a decrease of the 11-yrs moving average down to -20 %, for RCP4.5, and -50 %, for RCP8.5, even if characterized by relevant inter-annual fluctuations.