This paper presents a framework to assess how salmonids are affected by streambed scour caused by climate-related changes. We applied this framework specifically in the Middle Fork of the Salmon River, situated in central Idaho's Northern Rocky Mountains.
In regions where snow dominates, climate change is anticipated to have widespread impacts on aquatic ecosystems. These impacts include changes in stream temperatures, flow patterns, and the frequency of wildfires. In the western United States, ongoing warming trends are already influencing stream temperatures and flow patterns due to shifts in winter precipitation from snow to rain and drier summers.
The risk of critical scour, which refers to the mortality of embryos caused by streambed erosion exceeding the depth at which the eggs are buried, depends on several factors. These factors include the timing of floods in relation to the incubation periods of the embryos, the location of spawning within the stream network, and the depth at which the eggs are buried. Fall-spawning salmonids are particularly vulnerable in snowmelt-dominated basins where climate warming increases rainfall. This increase in rainfall leads to more frequent and intense winter flood events when the eggs of fall-spawning salmonids are in the streambed. Additionally, smaller fish with shallower egg burial depths may face greater risks from increased streamflows, resulting in more severe scouring.
To determine the daily streamflows for both present and future conditions, they used a hydrologic model called Variable Infiltration Capacity (VIC). This model is based on real-world data and calculates how water moves through the land. They applied the VIC model at a detailed resolution of 1/16th degree specifically for the Pacific Northwest region.
Using the output from the VIC model, they created hydrographs for different stream segments in the Pacific Northwest. These hydrographs show how the flow of water in the streams changes over time. They compared these modeled hydrographs with actual observed data and found that they matched well, especially for flow metrics that are important for the environment.
To focus on the specific period when salmon eggs are incubating, we narrowed down the annual hydrographs. This allowed us to examine the flow conditions during the critical incubation period for each salmon species. They used these flow conditions to analyze the probability of "critical scour," which refers to the risk of the stream eroding and damaging the buried salmon eggs. The frequency of critical scour is crucial because occasional scour can disrupt a particular year's salmon population, while frequent scour can significantly impact the overall viability of the population. With climate change causing increased flow in streams, they expect the frequency of critical scour to rise
The article examined how changes in stream discharge could affect the risk of scour. As the climate warms, the amount of water flowing in the streams is predicted to increase during the spawning season for salmon. We found that this could lead to more erosion of the streambed. However, the depth at which the salmon eggs are buried plays a role in determining the risk. Chinook salmon, which bury their eggs deeper, are less likely to be affected by increased flow.
This paper presents a framework to assess how salmonids are affected by streambed scour caused by climate-related changes. We applied this framework specifically in the Middle Fork of the Salmon River, situated in central Idaho's Northern Rocky Mountains.
In regions where snow dominates, climate change is anticipated to have widespread impacts on aquatic ecosystems. These impacts include changes in stream temperatures, flow patterns, and the frequency of wildfires. In the western United States, ongoing warming trends are already influencing stream temperatures and flow patterns due to shifts in winter precipitation from snow to rain and drier summers. The risk of critical scour, which refers to the mortality of embryos caused by streambed erosion exceeding the depth at which the eggs are buried, depends on several factors. These factors include the timing of floods in relation to the incubation periods of the embryos, the location of spawning within the stream network, and the depth at which the eggs are buried. Fall-spawning salmonids are particularly vulnerable in snowmelt-dominated basins where climate warming increases rainfall. This increase in rainfall leads to more frequent and intense winter flood events when the eggs of fall-spawning salmonids are in the streambed. Additionally, smaller fish with shallower egg burial depths may face greater risks from increased streamflows, resulting in more severe scouring.
To determine the daily streamflows for both present and future conditions, they used a hydrologic model called Variable Infiltration Capacity (VIC). This model is based on real-world data and calculates how water moves through the land. They applied the VIC model at a detailed resolution of 1/16th degree specifically for the Pacific Northwest region. Using the output from the VIC model, they created hydrographs for different stream segments in the Pacific Northwest. These hydrographs show how the flow of water in the streams changes over time. They compared these modeled hydrographs with actual observed data and found that they matched well, especially for flow metrics that are important for the environment. To focus on the specific period when salmon eggs are incubating, we narrowed down the annual hydrographs. This allowed us to examine the flow conditions during the critical incubation period for each salmon species. They used these flow conditions to analyze the probability of "critical scour," which refers to the risk of the stream eroding and damaging the buried salmon eggs. The frequency of critical scour is crucial because occasional scour can disrupt a particular year's salmon population, while frequent scour can significantly impact the overall viability of the population. With climate change causing increased flow in streams, they expect the frequency of critical scour to rise
The article examined how changes in stream discharge could affect the risk of scour. As the climate warms, the amount of water flowing in the streams is predicted to increase during the spawning season for salmon. We found that this could lead to more erosion of the streambed. However, the depth at which the salmon eggs are buried plays a role in determining the risk. Chinook salmon, which bury their eggs deeper, are less likely to be affected by increased flow.