The Issue: Ice jams can occur at the outlet of Osoyoos Lake on the border of Canada and the United States, resulting in a decrease or complete interruption in streamflow on the Okanogan River. Interruptions in streamflow can hinder the passage of anadromous fish and impact downstream water rights and water supply.
How the USGS helped: USGS scientists at the Washington Water Science Center examined the past frequency of ice jam occurrence on Osoyoos Lake by reviewing satellite images, streamflow, and lake level. By combining this data with meteorological data, the USGS assessed the environmental conditions associated with ice jam occurrence.
Ice Jams on Osoyoos Lake Reduce Flow in the Okanogan River
Ice jams occur as accumulations of ice that build up at the outlet of Osoyoos Lake on the border of Canada and the United States. These jams reduce streamflow in the Okanogan River and can result in a rise in lake levels in Osoyoos Lake. Decreased streamflow in the river can harm incubating salmon eggs by exposing them to air and freezing temperatures. Additionally, increased levels of Osoyoos Lake during this period have the potential to damage shoreline infrastructure and exceed allowable lake levels established by the International Joint Commission's International Osoyoos Lake Board of Control.
Identifying Historical Ice Jams
The USGS undertook an investigation, in cooperation with the International Joint Commission, to determine the frequency of ice jams on Osoyoos Lake and determine the environmental conditions under which ice jams tend to occur.
USGS scientists compiled streamflow, lake level, and weather data and identified typical conditions when known ice jams occurred historically. They also reviewed satellite imagery to visually confirm the presence of ice, ice jams, and to make observations about ice distribution on the lake during ice jam events. Once the scientists identified the changes in streamflow and lake level in response to ice jams, they looked for cold periods with similar abrupt reductions in streamflow in the Okanogan River associated with increased water levels in Osoyoos Lake to identify past ice jams going back further in time than satellite imagery and documented ice jams. This approach revealed 16 ice jam events that occurred since 1942, with ice jam conditions persisting a total of 31 days. Individual ice jams typically persisted for one to four days. Thirteen ice jam days occurred in the past decade (2014–2024), exceeding any previous decade.
Understanding the Environmental Conditions Associated with Ice Jams
With a list of historical ice jams in hand, the researchers investigated the weather conditions associated with these events. Weather stations in the Okanogan Valley provided historical wind speed and direction, as well as air temperature data. Statistical tests indicated significant differences in each of these weather conditions between ice jam and non-ice jam days.
Ice jams are more likely to occur when the wind blows from the west or the northwest and when wind speeds are near or above 6 miles per hour (10 kilometers per hour). Additionally, ice jams are more likely during cold periods when minimum air temperatures are near or below 15 degrees Fahrenheit (-9.4 degrees Celsius). The daily minimum air temperature in the Osoyoos Lake region has increased at a rate of 0.021 °C per year since the 1940s, but ice jams usually occur in winters with colder average temperatures.
The findings of this study suggest that ice jams form when strong wind pushes broken ice on the lake toward the southern outlet. Information about when ice jams occurred in the past will help water managers better understand these events and prepare for future occurrences.
The Issue: Ice jams can occur at the outlet of Osoyoos Lake on the border of Canada and the United States, resulting in a decrease or complete interruption in streamflow on the Okanogan River. Interruptions in streamflow can hinder the passage of anadromous fish and impact downstream water rights and water supply.
How the USGS helped: USGS scientists at the Washington Water Science Center examined the past frequency of ice jam occurrence on Osoyoos Lake by reviewing satellite images, streamflow, and lake level. By combining this data with meteorological data, the USGS assessed the environmental conditions associated with ice jam occurrence.
Ice Jams on Osoyoos Lake Reduce Flow in the Okanogan River
Ice jams occur as accumulations of ice that build up at the outlet of Osoyoos Lake on the border of Canada and the United States. These jams reduce streamflow in the Okanogan River and can result in a rise in lake levels in Osoyoos Lake. Decreased streamflow in the river can harm incubating salmon eggs by exposing them to air and freezing temperatures. Additionally, increased levels of Osoyoos Lake during this period have the potential to damage shoreline infrastructure and exceed allowable lake levels established by the International Joint Commission's International Osoyoos Lake Board of Control.
Identifying Historical Ice Jams
The USGS undertook an investigation, in cooperation with the International Joint Commission, to determine the frequency of ice jams on Osoyoos Lake and determine the environmental conditions under which ice jams tend to occur.
USGS scientists compiled streamflow, lake level, and weather data and identified typical conditions when known ice jams occurred historically. They also reviewed satellite imagery to visually confirm the presence of ice, ice jams, and to make observations about ice distribution on the lake during ice jam events. Once the scientists identified the changes in streamflow and lake level in response to ice jams, they looked for cold periods with similar abrupt reductions in streamflow in the Okanogan River associated with increased water levels in Osoyoos Lake to identify past ice jams going back further in time than satellite imagery and documented ice jams. This approach revealed 16 ice jam events that occurred since 1942, with ice jam conditions persisting a total of 31 days. Individual ice jams typically persisted for one to four days. Thirteen ice jam days occurred in the past decade (2014–2024), exceeding any previous decade.
Understanding the Environmental Conditions Associated with Ice Jams
With a list of historical ice jams in hand, the researchers investigated the weather conditions associated with these events. Weather stations in the Okanogan Valley provided historical wind speed and direction, as well as air temperature data. Statistical tests indicated significant differences in each of these weather conditions between ice jam and non-ice jam days.
Ice jams are more likely to occur when the wind blows from the west or the northwest and when wind speeds are near or above 6 miles per hour (10 kilometers per hour). Additionally, ice jams are more likely during cold periods when minimum air temperatures are near or below 15 degrees Fahrenheit (-9.4 degrees Celsius). The daily minimum air temperature in the Osoyoos Lake region has increased at a rate of 0.021 °C per year since the 1940s, but ice jams usually occur in winters with colder average temperatures.
The findings of this study suggest that ice jams form when strong wind pushes broken ice on the lake toward the southern outlet. Information about when ice jams occurred in the past will help water managers better understand these events and prepare for future occurrences.