Six months ago, when I stood on this bridge over Waskerley beck, which flows from the head of the Tunstall valley, the reservoir that it supplies was brimful. A rapid thaw after late heavy snowfall, followed by torrential rain, had left a pair of great-crested grebes piling up water weeds in a desperate attempt to keep their nest site above rising flood water.

Easy pickings for a heron fishing for trout in Tunstall reservoir’s shallow margins. Photograph: Phil Gates

Today, after the driest summer I can remember, a third of what was 66 acres of deep water is still mud. The sluggish beck meanders through the sediment towards a shallow lake, its rate of flow akin to replenishing an empty swimming pool using an egg cup. It will take many weeks of heavy rain to recharge the groundwater in the surrounding fells to the point where a refilled reservoir will cascade over the dam wall spillway again.

Tunstall reservoir, built in 1879 to store drinking water, is now relegated to the role of maintaining summer water flow in the River Wear, three miles downstream at Wolsingham. It has been stocked with rainbow trout and all summer they have become concentrated in a shrinking volume of water. I counted 12 fishermen this morning: only one was using a rod and line; six were cormorants and five were herons, taking full advantage of such easy feeding opportunities. The idiom “shooting fish in a barrel” came to mind.

I walked home through Backstone Bank wood, ancient oak woodland on the eastern flank of the reservoir, across a wooden bridge over another stream, where the trickle of water barely disturbed the autumn leaves that spun down into its rocky bed.

A trickle of water, barely enough to disturb fallen leaves, in a woodland stream that flows into Tunstall reservoir. Photograph: Phil Gates

The morning’s climate change news had been of a Met Office report describing a pattern of wetter winters and longer, drier summers. The reservoir’s water level has sometimes been low in the past, but it seems likely that this year’s exceptional weather experience will become the new normal. I’ve known this secluded valley for most of my life, with its farms, fellsides, wetlands and woodlands, all interlinked. There is now a sense of urgency in appreciating the here and now, before too much changes too fast.