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.
Regional Water Availability Assessments are detailed scientific studies of water availability, conducted in medium-sized watersheds located throughout the Nation. These Integrated Water Availability Assessments, occurring in Integrated Water Science basins, evaluate water quantity and quality in both surface and groundwater, determine whether there is enough water for human and ecosystem needs, and understand how human and natural influences affect the amount of available water. Regional Water Availability Assessments address important water resource questions in the basin in ways that support local stakeholders and improve the USGS’s national water availability assessment capacity.
The Colorado River and its tributaries supply drinking water for 40 million people in the U.S. and Mexico, irrigation water for 5.5 million acres of land, and are essential sources of water for at least 29 federally recognized tribes, 7 National Wildlife Refuges, 4 National Recreation Areas, and 11 National Parks (Bureau of Reclamation, 2012; Bureau of Reclamation and Colorado River Basin Ten Tribes Partnership, 2018). The Upper Colorado River Basin (UCOL) was selected as an Integrated Water Science basin in 2019. The UCOL water availability assessment studies will focus on the area of the UCOL watershed upstream of Lee’s Ferry, Arizona. A smaller sub-basin that includes the Colorado headwaters and Gunnison River Basins is being intensively monitored by the Next Generation Water Observing System (NGWOS).
Accumulation of an annual winter snowpack in the mountains and subsequent spring snowmelt are primary drivers of hydrology of the UCOL. High-altitude areas in the UCOL are cold enough to receive most of their precipitation as winter snow that accumulates as a seasonal snowpack. These areas produce a large portion of the runoff to streams in the basin, where about 15 percent of the basin area contributes about 85 percent of the mean-annual runoff (Lukas and Payton, 2020). Snow that falls and accumulates in the UCOL headwaters is eventually delivered to and stored in two major reservoirs - Lake Powell and Lake Mead. These reservoirs serve as critical water supplies for the Lower Colorado River basin. A 2022 UCOL Regional Water Availability Assessment publication summarizes the state of snow, and other priority water availability components in the UCOL, including streamflow, total dissolved solids (TDS; a proxy for salinity) in groundwater and surface water, and groundwater levels and storage. Each of these components plays an important role in understanding the UCOL water cycle and water quality.
Upper Colorado River Basin Regional Water Availability Phases
Phase 1 of the Regional Water Availability Assessment, which formally began in 2021, will last five years and will focus on addressing a regionally relevant threat to water availability. Phase 2 of the assessment will begin in 2026, will last five years, and will include a broader regional evaluation of water supply and demand.
Regional Water Availability Assessments in IWS Basins are conducted in two general Phases:
Phase 1 - Focus topic: A focused assessment of regionally relevant threats to water availability
Regional Assessments begin in Phase 1 by addressing regionally important water resource questions in ways that both support local stakeholders and improve national assessment capacity. A small number of focus topics are identified by the USGS Water Mission Area at the time of IWS Basin selection, guided by national model gaps and stakeholder needs in the basin. This phase of the assessment will (1) answer key science questions in the region related to the focus topic; (2) develop new process understanding and modeling capacity that fills a gap in the region and supports national models and assessments; and (3) predict future changes in water availability for humans or aquatic life, as related to the focus topic.
Owing to the importance of snow processes on UCOL hydrology and water quality, the UCOL focus topic addresses the effects of snow conditions on water availability. The goal of Phase 1 is to improve understanding of how snow accumulation and melt processes contribute to surface and groundwater availability. Specifically, Phase 1 will address two primary water availability questions:
- How have changes in snowpack in the UCOL headwaters translated to changes in other water budget components throughout the basin and how will these changes vary in the future?
- What is the sensitivity of total dissolved solids concentrations and loads to changes in snow hydrology?
Changes in climate are affecting the amount of snow accumulation, the timing of snow melt, and the relative contribution of precipitation that falls as rain versus snow (Mote and others, 2018; Milly and Dunne, 2020; Musselman and others, 2021). These changes are expected to continue in the future (Talsma and others, 2022), and projecting the effects of these changes on water availability is required to help inform plans for meeting future water demand in the basin.
Phase 2 - Base evaluation: A regional evaluation of water supply and demand
The Regional Assessments continue in Phase 2 with a broader evaluation—an integrated and comprehensive evaluation of factors affecting water availability in the region, inclusive of water quantity, quality, and use. This base evaluation will explore targeted future tipping points —when water no longer meets our standards for a given use — and human and ecosystem vulnerabilities in the region. A consistent approach will be used in each Regional Assessment to allow for comparing and contrasting limits to past, current, and future water availability in different parts of the Nation in more detail than will be possible using national-scale assessments. The regional base evaluation will complement the National Water Availability Assessment by answering similar water availability questions, but in more detail, and tailored toward important regional water issues.
Below are other science projects associated with IWAAs and the Upper Colorado River Basin.
Integrated Water Availability Assessments
Regional Water Availability Assessment: Delaware River Basin
Integrated Water Science (IWS) Basins
Next Generation Water Observing System (NGWOS)
Integrated Water Prediction (IWP)
Next Generation Water Observing System: Upper Colorado River Basin
Below are data releases associated with IWAAs and the Upper Colorado River Basin.
Groundwater-withdrawal and well-construction data in the Upper Colorado River Basin from Arizona, Colorado, New Mexico, Utah, and Wyoming state databases, 1980–2022
Digital hydrogeologic framework model of the Upper Colorado River Basin, western U.S.
Below are publications associated with IWAAs and the Upper Colorado River Basin.
A review of current capabilities and science gaps in water supply data, modeling, and trends for water availability assessments in the Upper Colorado River Basin
How will baseflow respond to climate change in the Upper Colorado River Basin?
Water priorities for the Nation—USGS Integrated Water Science basins
Substantial declines in salinity observed across the Upper Colorado River Basin during the 20th century, 1929 to 2019
Water priorities for the Nation—U.S. Geological Survey Integrated Water Availability Assessments
Below are data or web applications associated with IWAAs and the Upper Colorado River Basin.
From Snow to Flow (data visualization story)
A majority of the water in the western U.S. comes from snowmelt, but changes in the timing, magnitude, and duration of snowmelt can alter water availability downstream. This data visualization story explores what changing snowmelt means for water in the West, and how new USGS efforts can advance snow science by modeling snowpack and snowmelt dynamics and linking these results to streamflow.
- Overview
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.
Regional Water Availability Assessments are detailed scientific studies of water availability, conducted in medium-sized watersheds located throughout the Nation. These Integrated Water Availability Assessments, occurring in Integrated Water Science basins, evaluate water quantity and quality in both surface and groundwater, determine whether there is enough water for human and ecosystem needs, and understand how human and natural influences affect the amount of available water. Regional Water Availability Assessments address important water resource questions in the basin in ways that support local stakeholders and improve the USGS’s national water availability assessment capacity.
The Colorado River and its tributaries supply drinking water for 40 million people in the U.S. and Mexico, irrigation water for 5.5 million acres of land, and are essential sources of water for at least 29 federally recognized tribes, 7 National Wildlife Refuges, 4 National Recreation Areas, and 11 National Parks (Bureau of Reclamation, 2012; Bureau of Reclamation and Colorado River Basin Ten Tribes Partnership, 2018). The Upper Colorado River Basin (UCOL) was selected as an Integrated Water Science basin in 2019. The UCOL water availability assessment studies will focus on the area of the UCOL watershed upstream of Lee’s Ferry, Arizona. A smaller sub-basin that includes the Colorado headwaters and Gunnison River Basins is being intensively monitored by the Next Generation Water Observing System (NGWOS).
Accumulation of an annual winter snowpack in the mountains and subsequent spring snowmelt are primary drivers of hydrology of the UCOL. High-altitude areas in the UCOL are cold enough to receive most of their precipitation as winter snow that accumulates as a seasonal snowpack. These areas produce a large portion of the runoff to streams in the basin, where about 15 percent of the basin area contributes about 85 percent of the mean-annual runoff (Lukas and Payton, 2020). Snow that falls and accumulates in the UCOL headwaters is eventually delivered to and stored in two major reservoirs - Lake Powell and Lake Mead. These reservoirs serve as critical water supplies for the Lower Colorado River basin. A 2022 UCOL Regional Water Availability Assessment publication summarizes the state of snow, and other priority water availability components in the UCOL, including streamflow, total dissolved solids (TDS; a proxy for salinity) in groundwater and surface water, and groundwater levels and storage. Each of these components plays an important role in understanding the UCOL water cycle and water quality.
Upper Colorado River Basin Regional Water Availability Phases
Phase 1 of the Regional Water Availability Assessment, which formally began in 2021, will last five years and will focus on addressing a regionally relevant threat to water availability. Phase 2 of the assessment will begin in 2026, will last five years, and will include a broader regional evaluation of water supply and demand.
The Upper Colorado River Basin regional water availability assessment is divided into two phases. Regional Water Availability Assessments in IWS Basins are conducted in two general Phases:
Phase 1 - Focus topic: A focused assessment of regionally relevant threats to water availability
Regional Assessments begin in Phase 1 by addressing regionally important water resource questions in ways that both support local stakeholders and improve national assessment capacity. A small number of focus topics are identified by the USGS Water Mission Area at the time of IWS Basin selection, guided by national model gaps and stakeholder needs in the basin. This phase of the assessment will (1) answer key science questions in the region related to the focus topic; (2) develop new process understanding and modeling capacity that fills a gap in the region and supports national models and assessments; and (3) predict future changes in water availability for humans or aquatic life, as related to the focus topic.
Owing to the importance of snow processes on UCOL hydrology and water quality, the UCOL focus topic addresses the effects of snow conditions on water availability. The goal of Phase 1 is to improve understanding of how snow accumulation and melt processes contribute to surface and groundwater availability. Specifically, Phase 1 will address two primary water availability questions:
- How have changes in snowpack in the UCOL headwaters translated to changes in other water budget components throughout the basin and how will these changes vary in the future?
- What is the sensitivity of total dissolved solids concentrations and loads to changes in snow hydrology?
Changes in climate are affecting the amount of snow accumulation, the timing of snow melt, and the relative contribution of precipitation that falls as rain versus snow (Mote and others, 2018; Milly and Dunne, 2020; Musselman and others, 2021). These changes are expected to continue in the future (Talsma and others, 2022), and projecting the effects of these changes on water availability is required to help inform plans for meeting future water demand in the basin.
Phase 2 - Base evaluation: A regional evaluation of water supply and demand
The Regional Assessments continue in Phase 2 with a broader evaluation—an integrated and comprehensive evaluation of factors affecting water availability in the region, inclusive of water quantity, quality, and use. This base evaluation will explore targeted future tipping points —when water no longer meets our standards for a given use — and human and ecosystem vulnerabilities in the region. A consistent approach will be used in each Regional Assessment to allow for comparing and contrasting limits to past, current, and future water availability in different parts of the Nation in more detail than will be possible using national-scale assessments. The regional base evaluation will complement the National Water Availability Assessment by answering similar water availability questions, but in more detail, and tailored toward important regional water issues.
- Science
Below are other science projects associated with IWAAs and the Upper Colorado River Basin.
Integrated Water Availability Assessments
The USGS Water Resources Mission Area is assessing how much water is available for human and ecological needs in the United States and identifying where and when the Nation may have challenges meeting its demand for water.Regional Water Availability Assessment: Delaware River Basin
Regional Water Availability Assessments are scientific assessments of water availability in different hydrologic regions across the Nation. In the Delaware River Basin, the USGS will conduct a focused assessment of increasing freshwater salinity and an integrated and comprehensive assessment of multiple water quantity, quality and use factors.Integrated Water Science (IWS) Basins
The U.S. Geological Survey is integrating its water science programs to better address the Nation’s greatest water resource challenges. At the heart of this effort are plans to intensively study at least 10 Integrated Water Science (IWS) basins — medium-sized watersheds (10,000-20,000 square miles) and underlying aquifers — over the next decade. The IWS basins will represent a wide range of...Next Generation Water Observing System (NGWOS)
Substantial advances in water science, together with emerging breakthroughs in technical and computational capabilities, have led the USGS to develop a Next Generation Water Observing System (NGWOS). The USGS NGWOS will provide real-time data on water quantity and quality in more affordable and rapid ways than previously possible, and in more locations.Integrated Water Prediction (IWP)
The USGS Integrated Water Prediction science program focuses on the development of advanced models for forecasting multiple water quality and quantity attributes including water budgets and components of the water cycle; water use; temperature; dissolved and suspended water constituents, and ecological conditions. It is also developing the cyberinfrastructure and workflows required to implement...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... - Data
Below are data releases associated with IWAAs and the Upper Colorado River Basin.
Groundwater-withdrawal and well-construction data in the Upper Colorado River Basin from Arizona, Colorado, New Mexico, Utah, and Wyoming state databases, 1980–2022
The U.S. Geological Survey developed a coupled groundwater and surface-water flow (GSFLOW) model to represent the aquifers of the Colorado Plateau and Upper Colorado River Basin. The study area covers approximately 142,000 square miles and includes parts of Arizona, Colorado, New Mexico, Utah, and Wyoming. To support this modeling effort, groundwater well withdrawal volume data were needed from JaDigital hydrogeologic framework model of the Upper Colorado River Basin, western U.S.
This digital dataset was created as part of a U.S. Geological Survey hydrologic resource assessment and development of an integrated numerical hydrologic model of the hydrologic system of the Upper Colorado River Basin, an extensive region covering approximately 412,000 square kilometers in five states: Wyoming, Colorado, Utah, Arizona, and New Mexico. As part of this larger study, the USGS develo - Publications
Below are publications associated with IWAAs and the Upper Colorado River Basin.
A review of current capabilities and science gaps in water supply data, modeling, and trends for water availability assessments in the Upper Colorado River Basin
The Colorado River is a critical water resource in the southwestern United States, supplying drinking water for 40 million people in the region and water for irrigation of 2.2 million hectares of land. Extended drought in the Upper Colorado River Basin (UCOL) and the prospect of a warmer climate in the future pose water availability challenges for those charged with managing the river. Limited watAuthorsFred D. Tillman, Natalie K. Day, Matthew P. Miller, Olivia L. Miller, Christine Rumsey, Daniel Wise, Patrick Cullen Longley, Morgan C. McDonnellHow will baseflow respond to climate change in the Upper Colorado River Basin?
Baseflow is critical to sustaining streamflow in the Upper Colorado River Basin. Therefore, effective water resources management requires estimates of baseflow response to climatic changes. This study provides the first estimates of projected baseflow changes from historical (1984 – 2012) to thirty-year periods centered around 2030, 2050, and 2080 under warm/wet, median, and hot/dry climatic condiAuthorsOlivia L. Miller, Matthew P. Miller, Patrick Cullen Longley, Jay R. Alder, Lindsay A. Bearup, Tom Pruitt, Daniel Jones, Annie Laura Putman, Christine Rumsey, Tim S. McKinneyWater priorities for the Nation—USGS Integrated Water Science basins
The United States faces growing challenges to its water supply, infrastructure, and aquatic ecosystems because of population growth, climate change, floods, and droughts. To help address these challenges, the U.S. Geological Survey Water Resources Mission Area is integrating recent advances in monitoring, research, and modeling to improve assessments of water availability throughout the United StaAuthorsMark P. Miller, Sandra M. Eberts, Lori A. SpragueSubstantial declines in salinity observed across the Upper Colorado River Basin during the 20th century, 1929 to 2019
Salinity in the Colorado River Basin causes an estimated $300 to $400 million per year in economic damages in the U.S. To inform and improve salinity‐control efforts, this study quantifies long‐term trends in salinity (dissolved solids) across the Upper Colorado River Basin (UCRB), including time periods prior to the construction of large dams and preceding the implementation of salinity‐control pAuthorsChristine Rumsey, Olivia L. Miller, Robert Hirsch, Thomas M. Marston, David SusongWater priorities for the Nation—U.S. Geological Survey Integrated Water Availability Assessments
The United States faces growing challenges to its water supply, infrastructure, and aquatic ecosystems because of population growth, climate change, floods and droughts, and aging water delivery systems. To help address these challenges, the U.S. Geological Survey (USGS) Water Resources Mission Area has established new strategic priorities that capitalize on the operational and scientific strengthAuthorsMark P. Miller, Brian R. Clark, Sandra M. Eberts, Patrick M. Lambert, Patricia Toccalino - Web Tools
Below are data or web applications associated with IWAAs and the Upper Colorado River Basin.
From Snow to Flow (data visualization story)
A majority of the water in the western U.S. comes from snowmelt, but changes in the timing, magnitude, and duration of snowmelt can alter water availability downstream. This data visualization story explores what changing snowmelt means for water in the West, and how new USGS efforts can advance snow science by modeling snowpack and snowmelt dynamics and linking these results to streamflow.