Groundwater pollution threatens human and ecosystem health in many regions around the globe. Fast flow to the groundwater through focused recharge is known to transmit short-lived pollutants into carbonate aquifers, endangering the quality of groundwaters where one quarter of the world’s population lives. However, the large-scale impact of such focused recharge on groundwater quality remains poorly understood. Here, we apply a continental-scale model to quantify the risk of groundwater contamination by degradable pollutants through focused recharge in the carbonate rock regions of Europe, North Africa, and the Middle East. We show that focused recharge is the primary reason for widespread rapid transport of contaminants to the groundwater. Where it occurs, the concentration of pollutants in groundwater recharge that have not yet degraded increases from <1% to around 20 to 50% of their concentrations during infiltration. Assuming realistic application rates, our simulations show that degradable pollutants like glyphosate can exceed their permissible concentrations by 3 to 19 times when reaching the groundwater. Our results are supported by independent estimates of young water fractions at 78 carbonate rock springs over Europe and a dataset of observed glyphosate concentrations in the groundwater. They imply that in times of continuing and increasing industrial and agricultural productivity, focused recharge may result in an underestimated and widespread risk to usable groundwater volumes.
An automatic lineament extraction was carried out on a processed digi tal elevation model of a highaltitude Alpine fractured reservoir, the Pale di San Martino area (Dolomites) located in the southern sector of the Eastern Italian Alps. The strike of the main lineament domain indicates the direction of the principal crustal stress. This direction was compared with earthquake focal mechanisms to confirm the orientation of the regional crustal stress. The two data sets provide similar results and show a NNWSSE maximum horizontal crustal stress orientation, compatible with the direction of the last Alpine compression reported by previous studies in the investigated region. The orientation of the maximum horizontal compressive stress was then used to explore the ability of specific fracture and fault sets to enhance ground water flow. Subvertical strikeslip faults and joints oriented NWSE to north south provide the greater contribution to the groundwater flow. The location of the main springs and evidence from a dye tracer test conducted in the area confirm this main drainage direction. This study demonstrates that automatic lineament analysis is an efficient and inexpensive method to identify the tra jectories of groundwater flow in fractured aquifers.
Springs play a key role in the hydrology of mountain catchments and their water supply has a considerable impact on regional livelihood, biodiversity, tourism, and power generation. However, there is still limited knowledge of how rain and snow contribute to the recharge of Alpine springs. This study presents a four-year investigation of stable isotopes in precipitation and spring water at the scale of a 240 km2 wide dolomitic massif (Dolomites, Italian Alps) with the aim of determining the proportions of snowmelt and rain in spring water and to provide insights on the variability of these contributions in space and time. Four precipitation sampling devices were installed along a strong elevation gradient (from 725 to 2660 m a.s.l.) and nine major springs were monitored seasonally. The monitoring period comprised three extreme weather conditions, i.e., an exceptional snowpack melting period following the highest snowfall in 30 years, an intense precipitation event (386.4 mm of rain in 48 hours), and one of the driest periods ever observed in the region. Isotope-based mixing analysis revealed that rain and snowmelt contributions to spring water were noticeably variable, with two main recharge time windows: a late spring–summer snowmelt recharge period with an average snowmelt fraction in spring water up to 94 ± 9%, and a late autumn–early winter period with a rain fraction in spring water up to 68 ± 17%. Overall, during the monitoring period, snowmelt produced high-flow conditions and sustained baseflow more than rain. We argue that the seasonal variability of the snowmelt and rain fractions during the monitoring period reflects the relatively rapid and climate-dependent storage processes occurring in the aquifer. Our results also showed that snowmelt fractions in spring water vary in space around the mountain group as a function of the elevation of their recharge areas. High-altitude recharge areas, above 2500 m a.s.l., are characterized by a predominance of the snowmelt fraction (72% ± 29%) over the rain contribution. Recharge altitudes of approximately 2400 m a.s.l. also show a snow predominance (65 ± 31%), while springs recharged below 2000 m a.s.l. are recharged mostly from rain (snowmelt fraction of 46 ± 26%). Results from this study may be used to develop more accurate water management strategies in mountain catchments and to cope with future climate-change predictions that indicate a decline in the snow volume and duration in Alpine regions.
A 1:50,000 hydrogeological map of the Pale di San Martino Mountains (Northern Italy) was created. The map presents the merge of various pre-existing data with new field data collected between the years 2014 and 2016. Through the use of symbols and specific colours, the map shows various groundwater-related data such as the hydrogeological complexes, the location and size of the main springs, the extension of the recharge areas, the hydrogeological boundaries, as well as information on groundwater usage. Given the absence of hydrogeological maps in the entire mountain range of the Dolomites, the approach followed in this study could be used as a guide for future representations in this alpine region. At the local scale, the map could serve as a conceptual base for future research involving groundwater and for water management planning.
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