Lake Ellesmere/Te Waihora is famous not only as one of New Zealand’s most significant wetland habitats and largest lakes but also as one of its most polluted. Located beside the South Pacific just outside the city of Christchurch, the lake receives both surface and groundwater flows from one of the country’s most intensively farmed catchments. Combined with other environmental factors, this has led the lake to transform into a hypertrophic state, characterized by poor water quality and ecological health.

Although the lake’s health is poor, it still remains an area of cultural, natural, historic, recreational, and economic importance to many people. Its outstanding values are recognized in the National Water Conservation Order, which highlights its role as a habitat for wildlife, indigenous wetland vegetation, and fish, as well as its significance in accordance with tikanga Māori, particularly in relation to Ngāi Tahu history, mahinga kai (food gathering), and customary fisheries. The lake is also home to several small settlements around its shores, which now face an uncertain future as land leases expire and the risks of flooding and inadequate infrastructure grow.