Low river flows could pose ‘growing threat’ to water supplies – experts

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Low river flows and dry soils are putting landscapes under stress and could raise threats to supplies later in the year, experts have said.

The dry conditions come after many parts of the country have received below average rainfall since October 2021, and the recent heatwave put pressure on water supplies.

Already the conditions have posed challenges for farmers, put natural habitats under stress and fuelled wildfires, the UK Centre for Ecology and Hydrology (UKCEH) said.

Data from UKCEH shows that average river flows for June were “below normal” or “exceptionally low” across most of the country.

They were at their lowest on record for the month of June in some rivers, including the Yscir in south Wales, the Taw in Devon, and the Waveney in East Anglia.

River flows for most catchments have been exceptionally low since the spring, and in many rivers are approaching or below the levels at the equivalent time of year in past years of drought.

In a blog on the situation, Jamie Hannaford, principal hydrologist, said: “Increased demand from the heatwave has put short-term pressure on water supply, and should river flows continue to fall, there will be growing threats to water supply later in the year.

“Even now, low river flows are causing environmental stress in aquatic ecosystems and the dry soils have resulted in challenges for farmers, caused stressed terrestrial habitats and severe wildfires following the recent heatwave.”

Soils have also dried up, with figures from July 18 showing soil moisture was exceptionally low for many sites in southern, central and eastern England.

Groundwater levels were below normal or notably low in many boreholes around the country in June, and reservoir stocks were substantially below average, reflecting the low river flows, UKCEH said.

They were the lowest on record for June in Wales while some other reservoirs in parts of the Midlands and south-west England were 20% below average.

Current data suggests reservoir levels have continued to decline due to high evaporation and increased demand for water during the hot July spell.

Low river and groundwater levels reflect a long-term period of low rainfall, with large parts of southern, central and eastern England and Wales seeing severely or extremely dry conditions over the past six months, and a very dry start to July likely to worsen the situation.

In the south and east of the country, soil and groundwater stores are so dry that even very wet summer weather is unlikely to change the situation in the short term, the experts warned.

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