Kentmere Reservoir is a water storage facility situated in the Kentmere valley in the County of Cumbria, England. It is located 10.5 km north-northeast of the town of Windermere. The reservoir is fed by the streams which form the headwaters of The River Kent which rises 1.5 km to the north in Hall Cove on the southern slopes of High Street as well as Lingmell Gill which drains the large corrie on the western side of Harter Fell beneath the Nan Bield Pass.
The reservoir is built in area of volcanic and low-grade metamorphic (slatey) rocks, these are overlain by a wide tract of Silurian rocks comprising slates and grits. These very old “basement beds” are considered to be effectively impermeable . The reservoir covers an area of 19.5 hectares and holds 1020,000,000 litres of water. It has a 200 metre long dam wall with a stepped weir type overflow at the western end, there is a lower outlet for the River Kent in the middle of the dam wall. The reservoir's location is quiet and secluded surrounded by the fells of Yoke, Froswick, Ill Bell, Thornthwaite Crag, Harter Fell, Mardale Ill Bell and Kentmere Pike. These fells which make up the Kentmere horseshoe walk around the head and flanks of the Kentmere valley throw down steep slopes to the shore and give fine views of the reservoir.