Run-off from a large part of Orkney's West Mainland enters the sea via these two lochs. The shallow freshwater Loch of Harray becomes brackish at the junction with the Loch of Stenness, which is entirely brackish and classed as a lagoon. The flora and fauna therefore consists of brackish, marine and freshwater species. The lochs support large numbers of wintering wildfowl. Anser anser are from the Icelandic breeding population.