Looking northwest from Military Crossing Rd with the Williamson River in the foreground.
Satellite imagery and the interplay of climate and hydrologic data tell the story of surface-water decline in the Klamath Marsh.
The Klamath Marsh is a crucial part of the Williamson River Basin in southern Oregon, serving as a focal point for water draining the upper Williamson River and water flowing from the Cascade Range. Historically, surface-water outflow from Klamath Marsh supplied seasonally intermittent water to Upper Klamath Lake; however there has been no surface-water outflow from the marsh since 2020. Since 2020, hydrologists from the U.S. Geological Survey (USGS) and the Klamath Tribes are investigating the Klamath Marsh to better understand declines in standing water, declines in groundwater levels within and around the marsh, and declines in surface-water outflow from the marsh.
The amount of water in the Klamath Marsh increases seasonally each year in response to snowmelt runoff during the spring and early summer, and the wetted area gradually decreases through the summer and fall as the marsh dries out. Water in the marsh fluctuates naturally in response to year-to-year differences in the seasonal snowpack volume and melt timing. However, field observations by Klamath Tribes’ members and biologists noted that the extent of wetted area declined in recent decades.
To quantify changes in the annual maximum wetted area of the marsh, USGS hydrologists processed Landsat imagery to create a 37-year record of the annual maximum surface-water extent (MSWE) of the marsh. The MSWE dataset uses Landsat imagery from January through June of each year during 1985–2021 to document changes in surface-water cover within vegetated and open areas of the marsh. This geospatial dataset was published in December 2021.
Scientists compared the MSWE data to streamflow, groundwater level, precipitation, temperature, water use, water management, and changes in land cover to understand the possible factors influencing the observed changes in MSWE.
Result Highlights:
From 1985 through 2003 the MSWE yearly average was 22 percent of the total marsh area. However, during the second half of the study period, 2003–2021, the MSWE declined to 11 percent of the total marsh area. The results validated and quantified the field observations by Klamath Tribes’ scientists.
Sources/Usage: Public Domain. View Media Details
What factors likely contributed to a 50-percent reduction of water in the Klamath Marsh?
The hydrology of the Klamath Marsh relies on a delicate balance between groundwater level and surface-water inflow. The ground beneath the marsh is highly porous, so when the groundwater level is lower than the land surface, incoming streamflow infiltrates into the earth instead of staying on the surface and spreading out across the marsh. When the groundwater level is near the land surface and spring runoff is abundant, the wetted area (as measured by MSWE) is at its largest. In summer 2000, the groundwater level was at or above the marsh land surface, but by July 2021, groundwater had declined, leaving a 10- to 20-foot unsaturated zone (ground without water) beneath the marsh.
Streamflow inputs also decreased during the study period. The two stream gages in the area, Williamson River near Klamath Agency and Williamson River below Sheep Creek, had substantial declines in annual flow during 1985–2021.
Declines in streamflow and groundwater level could not be linked to human water use or management, nor were there any notable changes in precipitation during the 1985–2021 study period. Water declines in the marsh, groundwater level, and streamflow correspond with an increase in average air temperature across the region. During the study period, temperature increased at most climate stations, with lower-elevation areas experiencing an increase of 0.9-degrees Fahrenheit per decade. Therefore, climate-related changes in evapotranspiration (ET) may be contributing to the observed declines in wetland area within the marsh.
Re-establishment of more than 55,000 acres of forests following a county-wide decline in timber harvests after 1990 may also be contributing to increased levels of ET across the basin. ET within young pine forests has been documented to be larger than ET in older, more mature forests. As with rising temperatures, increased forest ET has the potential to reduce groundwater recharge which can reduce stream baseflow and contribute to the observed declines in groundwater level.
Increases in ET from rising air temperatures could stabilize or reverse if air temperatures decline; or if air temperatures continue to rise, vegetative thermal stress may limit plant growth causing them to use less water. Similarly, increases in ET by young trees in re-establishing forests could stabilize or reverse if forests are allowed to mature and are properly managed.
Regional studies of climate change and forest re-establishment and succession support the observed hydrologic changes in the Klamath Marsh. However, determining the relative importance of these factors (and potentially other unrecognized factors) on the hydrology of the Williamson River basin and Klamath Marsh will require continued and long-term scientific study. Along with hydrologists, understanding the complex interplay of climate change, wildfire, forest management, and restoration activities on the hydrology of the area requires expertise from many other fields of study. Planning is already underway for additional work by USGS in the Williamson River basin to inform these and other outstanding questions about the hydrology of the basin.
Sources/Usage: Public Domain. View Media Details
Photo's taken during research in the field:
Williamson River in the Klamath Marsh
Looking northwest from Military Crossing Rd with the Williamson River in the foreground.
Rain gage and piezometer at the Klamath Marsh, Oregon
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.
Rain gage and piezometer at the Klamath Marsh, Oregon
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.
Satellite imagery and the interplay of climate and hydrologic data tell the story of surface-water decline in the Klamath Marsh.
The Klamath Marsh is a crucial part of the Williamson River Basin in southern Oregon, serving as a focal point for water draining the upper Williamson River and water flowing from the Cascade Range. Historically, surface-water outflow from Klamath Marsh supplied seasonally intermittent water to Upper Klamath Lake; however there has been no surface-water outflow from the marsh since 2020. Since 2020, hydrologists from the U.S. Geological Survey (USGS) and the Klamath Tribes are investigating the Klamath Marsh to better understand declines in standing water, declines in groundwater levels within and around the marsh, and declines in surface-water outflow from the marsh.
The amount of water in the Klamath Marsh increases seasonally each year in response to snowmelt runoff during the spring and early summer, and the wetted area gradually decreases through the summer and fall as the marsh dries out. Water in the marsh fluctuates naturally in response to year-to-year differences in the seasonal snowpack volume and melt timing. However, field observations by Klamath Tribes’ members and biologists noted that the extent of wetted area declined in recent decades.
To quantify changes in the annual maximum wetted area of the marsh, USGS hydrologists processed Landsat imagery to create a 37-year record of the annual maximum surface-water extent (MSWE) of the marsh. The MSWE dataset uses Landsat imagery from January through June of each year during 1985–2021 to document changes in surface-water cover within vegetated and open areas of the marsh. This geospatial dataset was published in December 2021.
Scientists compared the MSWE data to streamflow, groundwater level, precipitation, temperature, water use, water management, and changes in land cover to understand the possible factors influencing the observed changes in MSWE.
Result Highlights:
From 1985 through 2003 the MSWE yearly average was 22 percent of the total marsh area. However, during the second half of the study period, 2003–2021, the MSWE declined to 11 percent of the total marsh area. The results validated and quantified the field observations by Klamath Tribes’ scientists.
Sources/Usage: Public Domain. View Media Details
What factors likely contributed to a 50-percent reduction of water in the Klamath Marsh?
The hydrology of the Klamath Marsh relies on a delicate balance between groundwater level and surface-water inflow. The ground beneath the marsh is highly porous, so when the groundwater level is lower than the land surface, incoming streamflow infiltrates into the earth instead of staying on the surface and spreading out across the marsh. When the groundwater level is near the land surface and spring runoff is abundant, the wetted area (as measured by MSWE) is at its largest. In summer 2000, the groundwater level was at or above the marsh land surface, but by July 2021, groundwater had declined, leaving a 10- to 20-foot unsaturated zone (ground without water) beneath the marsh.
Streamflow inputs also decreased during the study period. The two stream gages in the area, Williamson River near Klamath Agency and Williamson River below Sheep Creek, had substantial declines in annual flow during 1985–2021.
Declines in streamflow and groundwater level could not be linked to human water use or management, nor were there any notable changes in precipitation during the 1985–2021 study period. Water declines in the marsh, groundwater level, and streamflow correspond with an increase in average air temperature across the region. During the study period, temperature increased at most climate stations, with lower-elevation areas experiencing an increase of 0.9-degrees Fahrenheit per decade. Therefore, climate-related changes in evapotranspiration (ET) may be contributing to the observed declines in wetland area within the marsh.
Re-establishment of more than 55,000 acres of forests following a county-wide decline in timber harvests after 1990 may also be contributing to increased levels of ET across the basin. ET within young pine forests has been documented to be larger than ET in older, more mature forests. As with rising temperatures, increased forest ET has the potential to reduce groundwater recharge which can reduce stream baseflow and contribute to the observed declines in groundwater level.
Increases in ET from rising air temperatures could stabilize or reverse if air temperatures decline; or if air temperatures continue to rise, vegetative thermal stress may limit plant growth causing them to use less water. Similarly, increases in ET by young trees in re-establishing forests could stabilize or reverse if forests are allowed to mature and are properly managed.
Regional studies of climate change and forest re-establishment and succession support the observed hydrologic changes in the Klamath Marsh. However, determining the relative importance of these factors (and potentially other unrecognized factors) on the hydrology of the Williamson River basin and Klamath Marsh will require continued and long-term scientific study. Along with hydrologists, understanding the complex interplay of climate change, wildfire, forest management, and restoration activities on the hydrology of the area requires expertise from many other fields of study. Planning is already underway for additional work by USGS in the Williamson River basin to inform these and other outstanding questions about the hydrology of the basin.
Sources/Usage: Public Domain. View Media Details
Photo's taken during research in the field:
Williamson River in the Klamath Marsh
Looking northwest from Military Crossing Rd with the Williamson River in the foreground.
Looking northwest from Military Crossing Rd with the Williamson River in the foreground.
Rain gage and piezometer at the Klamath Marsh, Oregon
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.
Rain gage and piezometer at the Klamath Marsh, Oregon
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.
Looking south in the northern area of the Klamath Marsh. A white cylindrical rain gage that tracks rainfall and a white tube-shaped piezometer that measures changes in water level beneath the surface. These sensors are operated by the Klamath Tribes.