Sustainability of Groundwater Resources of Weathered and Fractured Schists in the Rural Areas of Galicia (Spain)

Abstract Water supply deficits in droughts, groundwater pollution and climate change are the main challenges for the sustainability of groundwater resources from hard rock aquifers in the rural areas of Galicia (Spain). Here we address the sustainability of groundwater resources of weathered and fractured schists in the rural areas of Abegondo municipality. The conceptualization of the hydrogeology of the study area includes: 1) The regolith, 2) The fractured rock layer; and 3) The underlying fresh bedrock. Groundwater flows mostly through the regolith and the fractured rock. Rainfall infiltration is the source of aquifer recharge. Groundwater discharges in seepage areas, springs and along creeks and valleys. The water table is generally shallow and shows seasonal oscillations of up to 4 m. The equivalent transmissivity ranges from 15 to 35 m2/d. Electrical resistivity tomography identifies a shallow water table and attests that the contact of the fractured rock and the fresh bedrock is highly heterogeneous. Groundwater resources were quantified with a hydrological water balance model. The mean annual recharge is approximately equal to 185 mm. Groundwater recharge at the end of the 21st century could decrease from 6% to 10% due to climate change. The decline in groundwater table could aggravate the shortages during droughts. Groundwater quality data show bacteriological and nitrate contamination due to a poor management of the manure in the fields and occasional discharges of slurry from pig and mink farms. Groundwater management and protection actions are proposed to prevent groundwater pollution and achieve a sustainable groundwater supply in the study area.