Photo of irrigation ditch flowing through a pasture in the East River Basin, Colorado.
Agricultural Return Flows in the Upper Gunnison River Basin
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By Colorado Water Science Center
April 3, 2025
Canals and ditches divert water from streams in the Upper Gunnison River Basin, Colorado, to irrigate agricultural fields. In some areas, irrigation water that percolates below the root zone can locally recharge groundwater and later return to streams through the subsurface, which can extend streamflow outside of the snowmelt runoff season. Understanding the timing and quantity of agricultural return flows can improve the understanding of possible effects from potential future changes in water availability and use.
The U.S. Geological Survey (USGS), in cooperation with the Upper Gunnison River Water Conservancy District, is studying groundwater and surface-water interactions in the East River, Upper Gunnison River Basin, to characterize the quantity and timing of agricultural return flows. The study area is a reach of the East River between two USGS streamgage sites:
- East River Below Cement Creek NR Crested Butte, CO - 09112200
- East River at Almont, Colorado - 09112500
Media
Sources/Usage: Public Domain. View Media Details
Media
Sources/Usage: Public Domain. View Media Details
Two approaches are used to characterize agricultural return flows in the study reach: (1) endmember mixing analysis, which relies on streamflow and geochemical data, and (2) groundwater modeling, which incorporates the physical processes of groundwater recharge and discharge with geochemical data. Both approaches provide information about the timing and quantity of agricultural return flows and can improve the understanding of this process in the Upper Gunnison River Basin. Project activities include the following:
- Collecting surface-water and groundwater samples for chemical analysis,
- Monitoring surface-water flows and groundwater levels,
- Completing endmember mixing analysis using geochemical tracers to estimate the fraction of streamflow represented by agricultural return flow, and
- Developing a groundwater-flow model to simulate groundwater and surface-water interactions
Colorado River Headwaters, Water Isotope Network
Water availability is controlled by processes that can be hard to measure, like the process of groundwater discharging from a streambed that becomes streamflow. Naturally occurring, radioactive and stable (non-radioactive) isotopes can help trace those processes, particularly the isotopes of hydrogen and oxygen that are part of the water molecule. Tritium, the radioactive isotope of hydrogen, has...
Regional Water Availability Assessment: Upper Colorado River Basin
Regional Water Availability Assessments are scientific assessments of water availability in different hydrologic regions across the Nation. In the Upper Colorado River Basin, the USGS will conduct a focused assessment of how snowpack and snowmelt influence hydrology and water quality, and an integrated and comprehensive assessment of multiple water quantity, quality and use factors.
Next Generation Water Observing System: Upper Colorado River Basin
The Next Generation Water Observing System (NGWOS) provides high-fidelity, real-time data on water quantity, quality, and use to support modern prediction and decision-support systems that are necessary for informing water operations on a daily basis and decision-making during water emergencies. The headwaters of the Colorado and Gunnison River Basins provide an opportunity to implement NGWOS in a...
Irrigation ditch in the East River Basin, Colorado
Photo of irrigation ditch flowing through a pasture in the East River Basin, Colorado.
09110500 East River Near Crested Butte, Colorado
The East River at U.S. Geological Survey streamgage site 09110500 (East River Near Crested Butte, Colorado.)
The East River at U.S. Geological Survey streamgage site 09110500 (East River Near Crested Butte, Colorado.)
Canals and ditches divert water from streams in the Upper Gunnison River Basin, Colorado, to irrigate agricultural fields. In some areas, irrigation water that percolates below the root zone can locally recharge groundwater and later return to streams through the subsurface, which can extend streamflow outside of the snowmelt runoff season. Understanding the timing and quantity of agricultural return flows can improve the understanding of possible effects from potential future changes in water availability and use.
The U.S. Geological Survey (USGS), in cooperation with the Upper Gunnison River Water Conservancy District, is studying groundwater and surface-water interactions in the East River, Upper Gunnison River Basin, to characterize the quantity and timing of agricultural return flows. The study area is a reach of the East River between two USGS streamgage sites:
- East River Below Cement Creek NR Crested Butte, CO - 09112200
- East River at Almont, Colorado - 09112500
Media
Sources/Usage: Public Domain. View Media Details
Media
Sources/Usage: Public Domain. View Media Details
Two approaches are used to characterize agricultural return flows in the study reach: (1) endmember mixing analysis, which relies on streamflow and geochemical data, and (2) groundwater modeling, which incorporates the physical processes of groundwater recharge and discharge with geochemical data. Both approaches provide information about the timing and quantity of agricultural return flows and can improve the understanding of this process in the Upper Gunnison River Basin. Project activities include the following:
- Collecting surface-water and groundwater samples for chemical analysis,
- Monitoring surface-water flows and groundwater levels,
- Completing endmember mixing analysis using geochemical tracers to estimate the fraction of streamflow represented by agricultural return flow, and
- Developing a groundwater-flow model to simulate groundwater and surface-water interactions
Colorado River Headwaters, Water Isotope Network
Water availability is controlled by processes that can be hard to measure, like the process of groundwater discharging from a streambed that becomes streamflow. Naturally occurring, radioactive and stable (non-radioactive) isotopes can help trace those processes, particularly the isotopes of hydrogen and oxygen that are part of the water molecule. Tritium, the radioactive isotope of hydrogen, has...
Regional Water Availability Assessment: Upper Colorado River Basin
Regional Water Availability Assessments are scientific assessments of water availability in different hydrologic regions across the Nation. In the Upper Colorado River Basin, the USGS will conduct a focused assessment of how snowpack and snowmelt influence hydrology and water quality, and an integrated and comprehensive assessment of multiple water quantity, quality and use factors.
Next Generation Water Observing System: Upper Colorado River Basin
The Next Generation Water Observing System (NGWOS) provides high-fidelity, real-time data on water quantity, quality, and use to support modern prediction and decision-support systems that are necessary for informing water operations on a daily basis and decision-making during water emergencies. The headwaters of the Colorado and Gunnison River Basins provide an opportunity to implement NGWOS in a...
Irrigation ditch in the East River Basin, Colorado
Photo of irrigation ditch flowing through a pasture in the East River Basin, Colorado.
Photo of irrigation ditch flowing through a pasture in the East River Basin, Colorado.
09110500 East River Near Crested Butte, Colorado
The East River at U.S. Geological Survey streamgage site 09110500 (East River Near Crested Butte, Colorado.)
The East River at U.S. Geological Survey streamgage site 09110500 (East River Near Crested Butte, Colorado.)