British Columbia’s Water Sustainability Act (WSA) formally defines the Environmental Flow Needs (EFNs) of a stream as “the volume and timing of water required for proper functioning of the aquatic ecosystem of the stream”, and requires the determination of EFNs for water bodies potentially affected by proposed licences for surface or groundwater extractions.
The WSA also defines another parameter, the Critical Environmental Flow Threshold (CEFT), as “the volume of water flow below which significant or irreversible harm to the aquatic ecosystem of the stream is likely to occur”, which is used by the province to manage water withdrawals during low flow periods.
The Okanagan Basin Water Board, the Okanagan Nation Alliance, and the provincial government, represented by the B.C. Ministry of Forests, Lands, Natural Resource Operations and Rural Development, initiated the Okanagan Environmental Flow Needs Project to determine the EFNs and CEFTs of each major stream in the Okanagan Basin.
The Phase 1 & 2 Summary Report identifies next steps for the Okanagan EFN project and summarizes the work completed to date.
The project’s key technical reports are posted here: