Lake Forsyth
Lake Forsyth (known to Māori as Te Roto o Wairewa) is a lake in the Canterbury region of New Zealand. It is fed by the Takiritawai River, a short arm of the Okuti River, and exits via a gravel bank into the sea in the vicinity of the small community of Birdlings Flat. State Highway 75 leading to Akaroa and part of the Little River Rail Trail follow the north-western shore of the lake. Lake Ellesmere / Te Waihora is nearby. Wairewa was an important for providing tuna [eel]s as food for the Ngai Tahu tribe (indigenous Maori  people of South Island). It is the only Ngai Tahu customary lake. Wairewa Runanga one of the 18 Ngai Tahu Runanga are the guardians or kaitiaki of the lake. However deforestation of the surrounding hills has led to erosion and silting up of the lake. The lake is hypertrophic, leading to eutrophication with corresponding poor water quality. This decline in water quality has been known since the early 1900s. So far, attempts of opening up the lake to the ocean to rectify the problem have had limited success. In 2016, after a spell of dry weather, the water quality deteriorated  and recurring algal blooms made the water toxic. Animals, including pets and sheep, died after drinking the water.