Revealing the importance of groundwater for potable private supplies in Wales

At least 77 000 people across Wales rely on private water supplies for their drinking water, with 94% of these supplies dependent on groundwater. Potable private water supplies were mapped to Lower Super Output Area level, creating the first map of its kind for Wales. Some rural areas report nearly 43% of properties using private water supplies as their principal source of water. Simplifying the complex geology of Wales into 'hydrostratigraphic units' shows that 97% of private water supplies are sourced from secondary aquifers that have low productivity and storage. Ordovician and Silurian bedrock aquifers and associated Quaternary deposits support nearly 75% of all private water supplies. The total volume of groundwater abstracted by licensed and unlicensed potable private water supplies across Wales is estimated at 24.6 Ml day(-1). In times of drought many of Wales' low-storage aquifers can experience insufficiency events. During 2018, reports of 132 dry supplies were collated; however, we suspect that many cases were not reported. In a changing climate with more extreme weather events, and as working from home becomes more common, private water supply users in low-storage and low-permeability aquifers may find themselves at increasing risk of insufficiency events.