Lower Bridge River, Xwisten Territory

Statistical modeling supporting water use planning in the Bridge River, BC

Client: Subcontract to Xwisten under contract to BC Hydro

Time: 2017 – present

Services: Study design, client support, data management and analysis in R and Primer7, statistical modeling in R, reporting.

Monitoring of juvenile salmonid production, periphyton and benthic invertebrate communities and their habitat in the Lower Bridge River (a tributary to the Fraser River, British Columbia) has been ongoing for more than 10 years as part of collection of data and related analyses and modeling that is supporting water use planning in the Bridge River hydroelectric complex. Limnotek has contributed to the water chemistry and lower trophic level data analysis and modeling since 2017 while partnering with Xwisten that is part of the St’át’imc Nation. Xwisten completed the annual field work. Funding is from BC Hydro.

The 23 year data record showed flow effects on lower trophic levels but they were strongly modified by presence/absence of Pink salmon. Very high flow induced scouring on benthic communities and lowered overall densities. Low and moderate flows produced high abundance and diversity in those same communities. The once every two year spawning cycle by Pinks was clearly evident in the metrics of biological production and diversity. Modeling revealed this interesting interplay between flow and nutrient availability and it showed a long term change in metrics of periphyton production potentially related to changing climate on water chemistry in glaciated source waters. Water use planning to meet needs of many users has indeed become complex but understandable when simplified using latest statistical modeling techniques at Limnotek.

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