Attachment - Bayesian analysis to map stream discharge and temperature causal effects pathways

Two collaborative modelling studies with Poisson Consulting underpin the stream temperature work described in the Methods chapter.

The 2024 study was carried out in this study area. It mapped stream discharge and temperature causal effects pathways across the Nechako Watershed, settling on a four-parameter air2stream formulation with site-level random effects — Spatial Stream Network Analysis of Nechako Watershed Stream Temperatures 2022b (Hill et al. 2024).

The 2025 study extended the approach to a larger spatial network in the Skeena and added Growing-Season Degree Days — accumulated thermal units during the season when stream temperature remains at or above 5 °C — as the productivity-relevant metric for age-0 salmonid growth — Spatial Stream Network Analysis of Skeena Watershed Stream Temperatures (Hill et al. 2025).

The water temperature observations feeding this work are organized in water-temp-bc (Irvine [2025] 2025b), which publishes Environment Canada hydrometric and water-quality records as a partitioned-parquet layer on Amazon S3.