The state of Tasman’s lakes is close to natural. This is mostly because nearly all the catchment area of Tasman District’s lakes is in native forest, and much of this is protected in conservation estate. Several one-off investigations into water quality and aquatic ecology have been carried out at most of Tasman's lakes.
Lakes of the District include:
- The large lakes in Nelson Lakes National Park (Lake Rotoiti and Lake Rotoroa), as well as some smaller ones (Lake Constance and Blue Lake)
- Lake Matiri and Lake Stanley in Kahurangi National Park.
- Kaihoka Lakes and Lake Otuihe (located north and south of Wanganui Inlet respectively). There is a small amount of sheep and beef farming in the catchments of these West Coast lakes.
- Cobb Reservoir, a moderate-sized impoundment whose catchment is nearly all within Kahurangi National Park.