Jersey reservoir will be emptied over the summer
Val de la Mare reservoir is going to be refurbished over the summer and the desalination plant will be put on standby by Jersey Water.
The water company will be installing a water-tight "membrane" to prolong the life of the dam.
During the work, both the top and lower car parks will stay open and walkers will still be able to follow the various routes from the top car park.
But the path at the dam to the lower part of the reservoir will be closed.
Between May and August, Queen's Valley and the other reservoirs will be kept as full as possible, and used whilst Val de la Mare is out of service.
Jersey Water said islanders should use water efficiently in the summer particularly with recent dry weather and the nature of the work being carried out.
They were also working closely with the Environment Department and the Jersey Freshwater Angling Association to make sure fish stocks in the reservoir were transferred safely to other locations.