Llwyn-on reservoir in Merthyr - press photography

MERTHYR TYDFIL, WALES - JULY 25: A general view of the Llwyn-on Reservoir, owned by Welsh Water, in the Taf Fawr valley on July 25, 2018 in Merthyr Tydfil, Wales. The lack of rainfall over the last few weeks combined with record breaking temperatures is having a dramatic effect on water levels in reservoirs. (Photo by Matthew Horwood/Getty Images)

MERTHYR TYDFIL, WALES - JULY 25: A girl crosses a bridge at the Llwyn-on Reservoir, owned by Welsh Water, in the Taf Fawr valley on July 25, 2018 in Merthyr Tydfil, Wales. The lack of rainfall over the last few weeks combined with record breaking temperatures is having a dramatic effect on water levels in reservoirs. (Photo by Matthew Horwood/Getty Images)

MERTHYR TYDFIL, WALES - JULY 25: A general view of the Llwyn-on Reservoir, owned by Welsh Water, in the Taf Fawr valley on July 25, 2018 in Merthyr Tydfil, Wales. The lack of rainfall over the last few weeks combined with record breaking temperatures is having a dramatic effect on water levels in reservoirs. (Photo by Matthew Horwood/Getty Images)