Minimum flows for sustaining summer water quality in constructed fish habitat in the lower mainland of British Columbia

Abstract

Constructed fish habitat is created to offset destroyed and degraded fish habitat. Reviews from government and research organizations indicate that constructed fish habitats often do not function as intended. To address this shortcoming, a summer survey of 26 constructed off-channel fish habitats in the Lower Mainland of British Columbia was conducted in 2019 to quantitatively assess design features of constructed fish habitats. Linear regression was used to estimate minimum turnover flows needed to sustain appropriate water quality for salmonids during rearing summer conditions. Model results suggest that flows of approximately 1 L/s are required to maintain water quality in 70 m3 of habitat volume and indicate that proximity to development increases the flows needed to sustain water temperatures. These findings are intended for use by biological practitioners and regulators to estimate minimum flow requirements for constructed fish habitat at the planning stage in advance of construction.