The hidden alternative - Assisted Natural Recovery
United Utilities proposal is to remove the dam, lower the lake and restore a natural river flow. In many rivers this would be an ideal solution, so why not here and what is the alternative?
The glacial lakes of Buttermere, Loweswater and Crummock retain their water through a stopper or plug of morraine - rocks and mud. The morraine is transported from the mountains via the becks where it is washed down the rivers to the sea. Piles of morraine build up at the edges of lakes where it builds up on rock formations. Anyone looking at the termination of Park beck can see the vast quantities of mud and gravel that pile up as it enters the lake. Water is often retained in natural lakes by terminal morraine - the pile of rock, stone and mud left as the glaciers melted.
Crummock was naturally ‘plugged’ at its Northern outflow. In 1878 teams of navvies excavated the plug and installed a wooden weir to enable drinking water to be extracted. Once installed they recreated a natural outflow. Since then the outflow has been rebuilt at least twice and peak water levels increased by 60cm.
When United Utilities first considered a scheme to renaturalise Crummock, they asked International Engineering consultants Jacobs to conduct an assessment and option appraisal. Their full report is here.
Jacobs considered a number of options. Scoring the best was ‘assisted natural recovery’ (in blue). The full weir removal (red) had some significant red flags including concerns over the impact on arctic charr. Go to page 163 of the report to read more detail.
Jacobs - Crummock option appraisal
Whilst no specific scheme for assisted natural recovery was developed by the UU project team, the principle is simple. The working parts of the weir are removed as is the top section of wave wall. The concrete weir is retained and buried within a new natural landscape. This allows the river to return to its natural function. The river outlet would look much like it did before man interferred.
Crucially, the lake level is retained as it is ensuring the impact on the environment is minimal. There is little construction necessary. Below is a painting by Heaton Cooper to help us imagine how it would look.
Our thanks to Julian Heaton Cooper for the use of this image
United Utilities discounted this option because in their opinion it would not release them from their obligations under the Reservoirs Act since there would be a head of water above a man made structure which would need continued supervision.
However, release from the Act is not necessary for planning purposes or for renaturisation. Residents of Lorton, Cockermouth and Workington may sleep easier knowing that the lake continues to be supervised by a water company during periods of heavy rainfall. See our previous article on flooding.
Many Friends of Crummock support the renaturalisation of our rivers and lakes. David Scott, an Environmental Specialist with in depth knowledge of Crummock and the Cocker explained: “Assisted natural recovery would preserve the established marginal ecology of the lake and fishery. This could also hold in reserve the option of the future use of the lake as a water supply”.