Redberry Lake (Saskatchewan)

Over the past several decades, Redberry Lake water levels have been declining and the salt concentrations increasing. With the declining levels, the shoreline length has been decreasing and the size of the islands in the lake have been increasing. In 1957, a new island — New Tern Island — appeared. In the 1940s, the salt content was low enough that there was a thriving commercial whitefish industry at the lake.

Lake levels and salinity

Redberry Lake water levels have been steadily declining and getting saltier over the past several decades. In 1974, the surface of the lake had an elevation of 515 m (1,690 ft) and an area of 53.42 km² (20.63 sq mi). That compares to 507 m (1,663 ft) and 51.69 km² (19.96 sq mi) in the mid-2020s. In 1926, the salt concentration was 12g/L and by 1988 that had doubled to 24g/L. The increase was attributed to "declining lake depth during drought". Magnesium, sodium, and sulphate make up most of the salt in Redberry Lake.

In 1940–41 with the salt content at only 15g/L, Donald Rawson from the University of Saskatchewan's biology department stocked Redberry Lake with whitefish (Coregonus clupeaformis). The fish thrived and in 1946 a commercial fishery was established. By 1981, though, the salt content had reached 20g/L and the fish could not survive, thus ending the fishery.