The following statement is from United Utilities regarding the management of Crummock water levels.
“Crummock Water provides water supplies to Workington, Cockermouth and surrounding areas. There is a small weir at the outlet of the lake with two central penstocks that can be opened at times of very dry weather when the water level in the lake falls below the crest of the weir. In this situation, water flows via the penstocks from the lake and into the River Cocker downstream to maintain a minimum flow of water.
The weir and the two central penstocks provide no level control function in normal weather or flood conditions. Water overflows the weir for most of the year and the weir only provides water level control during very dry weather situations.
It is important to note that United Utilities is not permitted to abstract any water from Crummock Water once the lake level falls 1 metre below the crest level of the weir. If large sluice gates were installed at the weir to lower the lake levels for flood storage, it would not be possible to hold the lake at a lower level and still reliably abstract water for supply to the people of Workington, Cockermouth and surrounding areas.
Even without this operational constraint, the amount of water that could be released by sluices at the weir would have been negligible in comparison to the inflows to the lake during October and November such were the rainfall volumes in this period.
This is a different situation to Thirlmere which is a large man-made reservoir where levels can fluctuate by over 10 metres in most years. By contrast, Crummock Water is a lake with a very small weir to provide only 1 metre of additional storage for public water supply.”