The work will prevent Himalayan balsam from overrunning the Site of Special Scientific Interest (SSSI).
The reservoir supplies water to the Peak Forest Canal and was designated a SSSI in 1986 because it is the home of an unusual community of short-lived mosses and liverworts which thrive on the muddy banks.
The reservoir is also made up of a combination of woodland, grassland and water margin habitats which support over 40 species of breeding birds including great crested grebe, little ringed plover, snipe and lapwing.
Himalayan balsam was introduced as a garden plant to this country in the early 19th Century, but has since spread into the wild with the easy to identify pink flowered plant mostly found on river banks and in other damp habitats.
The plant is spread when distinctive seed pods ‘explode' when disturbed, scattering the seeds up to seven metres away. The seeds can easily be carried in water and once they start to grow can overwhelm native plants very quickly.
Canal & River Trust ecologist Tom King said: “Himalayan balsam is an extremely invasive plant and once it becomes established can overwhelm native species leaving nothing but the invasive plant. Combs Reservoir is a very important Site of Special Scientific Interest and although Himalayan balsam can look like an attractive plant, especially when in flower, it can be very harmful to native species.
“While the short lived mosses and liverworts found at Combs Reservoir may seem like insignificant plants they are very are rare and important to the ecology of the site, which is why we must protect them.
“The woodland and grasslands around the reservoir are also very important for breeding birds and were these sites to be lost to Himalayan balsam it would be a tragedy for the reservoir and its status as an SSSI.
“We will be cutting down the alien invader by strimming it, which will protect the grasses underneath and allow them to grow, which they would have been unable to do with the thick canopy of Himalayan balsam over them.
“While strimming might seem like drastic action, leaving the banks of the reservoir bare in the short term, the native species will soon grow back again, regaining the native look of the reservoir.”