Fraser River environmental watch report September 14, 2020
Ten-day daily forecasts of lower Fraser River temperature and flow conditions as well as current conditions throughout the Fraser basin are updated bi-weekly from roughly late-June until mid-August. These short-range forecasts are generated using river temperature and river flow forecast models (Hague and Patterson 2014).
The latest research on Pacific salmon freshwater migration suggests there are population-specific differences in temperature and flow tolerance thresholds (Eliason et al. 2011). These differences likely relate back to the variability in the average river environmental conditions experienced by salmon beginning their river migration at different times of the year and along different paths (Farrell et al. 2008). Despite these differences, there are also species-wide thresholds that will result in migration difficulties for most populations of Fraser River sockeye salmon. We provide species-level thresholds as a guide to interpreting the potential effect of current and forecasted river temperature and flow conditions on returning salmon. However, in general, fish historically returning to the Fraser River in the mid-summer will be more tolerant of higher temperatures than those fish returning in the early or late summer or early fall.
| September 13, 2020 | Daily mean | Historic mean |
|---|---|---|
| Stuart River @ Fort St. James | 15.2 | 14.3 |
| Stellako River @ Glenannan | 16.0 | 14.9 |
| Nautley River @ Fort Fraser | 16.2 | 15.1 |
| Nechako River @ Vanderhoof | 16.4 | 13.7 |
| Nechako River @ Isle Pierre | 16.8 | 14.7 |
| Fraser River @ Shelley | 12.9 | 11.3 |
| Quesnel River @ Quesnel | 14.3 | 14.4 |
| Fraser River @ Marguerite | 14.3 | 13.7 |
| Chilcotin River @ Hanceville | NA | 12.2 |
| Fraser River @ Texas Creek | 15.2 | 14.7 |
| North Thompson River @ McLure | 14.8 | 13.1 |
| South Thompson River @ Chase | 18.0 | 17.7 |
| Thompson River @ Ashcroft | 17.6 | 16.8 |
| Thompson River @ Spences Bridge | 18.8 | 17.5 |
| Fraser River @ Big Bar Creek | NA | NA |
| Fraser River @ Hope | 16.2 | 14.8 |
Fraser River discharge at Hope
Critical levels for fish passage through Fraser Canyon:
- 7000 cms - Early signs of physiological stress evident
- 8000 cms - Difficultly in migration delaying migration time.
- 9000 cms - Barrier to migration through Hell's Gate.
Long text version
Graph showing Fraser River mean water discharge at Hope. Graph shows 2020 observed and predicted mean daily discharge, 20 year historic median and 20 year return period (1912 to 2019). Trend lines show a steady rate then a gradual decline starting mid-June.
Fraser River water temperatures at Hope
- 18°C - Decreased swimming performance
- 19°C - Early signs of physiological stress and slow migration
- 20°C - Associated with high pre-spawn mortality and disease
- 21°C - Chronic exposure can lead to severe stress and early mortality.
Long text version
Graph showing Fraser River mean water temperatures at Hope. Graph shows 2020 observed and predicted temperatures, highest observed (1950 to 2019) and historic mean (1912 to 2019). Trend lines show an increase from June to a high in August, and a decline to lows in September.
Fraser River discharge above Texas Creek
Long text version
Graph showing Fraser River mean daily discharge above Texas Creek. Graph shows 2020 observed and predicted mean daily discharge, historic median (1912 to 2019) and 20 year return period (1952 to 2019). Trend lines show a gradual decline from June to September.
Fraser River water temperatures above Texas Creek
Long text version
Graph showing Fraser River mean daily water temperatures above Texas Creek. Graph shows 2020 observed and predicted temperatures, highest observed (1996 to 1998, 2002 to 2019) and historic mean (1996 to 1998, 2002 to 2019). Trend lines show an increase from June to July, then a decline to lows in September.
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