This project presents the results of analyzes of the biodiversity of Tohé Lake and the land use of its watershed including along the water drainage channel of the SCANTOGO quarry at the lake. It also presents the results of physicochemical analyzes of the lake and the waters of the pumping station of the quarry. After analysis of the results (inventory and water analysis), it appears that the quarry waters do not contain nitrogen which should show traces of nitrate in the water of the quarry pumping station and against lake waters contain it. However, nutrients and toxic substances from market garden activities along the canal pass through the lake. Nutrient values such as nitrogen and phosphorus from laboratory water analyzes indicate that the lake is at an advanced stage of eutrophication. The eutrophication of the lake would therefore be mainly caused by the development of market gardening activities around the lake and intensified by the same activities along the drainage channel of the quarry's water using chemical inputs, herbicides and pesticides. The deforestation phenomenon in the watershed could also contribute by adding nutrients and sediments to the lake through soil erosion. Thus, it is necessary to: reduce the input of fertilizers to the lake from market gardening activities; increase wooded areas in the lake watershed.