And I wonder if they modeled the manipulation of water flows in their estimates. Seems man is controlling the temperatures of the river.
New
Information Bulletin: Water Flow at Big Bar Landslide
Aug 9, 2019
Water flow management is critical to the success of salmon being able to navigate past the Big Bar Landslide. Without correct water conditions, it can be difficult or impossible for the migrating fish to travel past the obstruction zone.
If the water flow is too fast, salmon will not be able to move upriver since the current would be too strong. If the flow is too slow, it will leave shallow pools which the salmon would then be unable to leap out of. What is needed is water movement that is neither too slow nor too fast, but just right. At the slide site, water flow is 2,900 m3/s (cubic metres per second) at various times which is currently presenting a significant obstacle for fish passage.
There are many tools at Incident Command’s disposal to manage water flow. Large rock manipulation has been critical to the success of this project. Altering the rock landscape by removing, moving, or adding rock to the site can change water flow and velocity patterns to better allow fish movement.
Another tool is managing water flows from regulated tributaries upstream, including the Nechako River. Ongoing summer releases by Rio Tinto Alcan, from the Nechako River system, allows the cooling of water to help salmon; however, due to this emergency situation, the Province had ordered that flows be reduced to assist in operations at the slide while still meeting temperature requirements.
The Province is committed to working with Rio Tinto Alcan to ensure that releases from the facility balance the needs at the Big Bar Landslide and the resident fish in the Nechako, including the endangered sturgeon population.
Altered flow releases from the dam have assisted efforts at the Big Bar Landslide by providing stable water flows at the site; however, as of August 8, 2019, based on temperatures in the Nechako river predicted by Rio Tinto modelling, Rio Tinto Alcan was asked by the Province to release water to provide cooling and to immediately revert back to maintaining regular flows as per its summer temperature management program. Rio Tinto Alcan has accommodated this request.
https://www2.gov.bc.ca/assets/gov/p...-2019/19_71w20ay_water_flow_august_9_2019.pdf
To be neutral between right and wrong is to serve wrong.
Modelling the impacts of climate change on riverine thermal regimes in western Canada’s largest Pacific watershed
Aug 6, 2019
Abstract
Quantification of climate change impacts on the thermal regimes of rivers in British Columbia (BC) is crucial given their importance to aquatic ecosystems. Using the Air2Stream model, we investigate the impact of both air temperature and streamflow changes on river water temperatures from 1950 to 2015 across BC’s 234,000 km2 Fraser River Basin (FRB). Model results show the FRB’s summer water temperatures rose by nearly 1.0 °C during 1950–2015 with 0.47 °C spread across 17 river sites. For most of these sites, such increases in average summer water temperature have doubled the number of days exceeding 20 °C, the water temperature that, if exceeded, potentially increases the physiological stress of salmon during migration. Furthermore, river sites, especially those in the upper and middle FRB, show significant associations between Pacific Ocean teleconnections and regional water temperatures. A multivariate linear regression analysis reveals that air temperature primarily controls simulated water temperatures in the FRB by capturing ~80% of its explained variance with secondary impacts through river discharge. Given such increases in river water temperature, salmon returning to spawn in the Fraser River and its tributaries are facing continued and increasing physical challenges now and potentially into the future.