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
Abstract
:1. Introduction
2. Background
UCOL Hydrology, Water Quality, and Water Use
3. Review of Current UCOL Data, Modeling, and Trend Capabilities
3.1. Streamflow
3.1.1. Data
3.1.2. Modeling Capabilities
3.1.3. Trends
3.2. Salinity in Groundwater and Surface Water
3.2.1. Data
3.2.2. Modeling Capabilities
Ground Water
Surface Water
3.2.3. Trends
3.3. Groundwater Levels and Storage
3.3.1. Data
3.3.2. Modeling Capabilities
3.3.3. Trends
3.4. Snow
3.4.1. Data
3.4.2. Modeling Capabilities
3.4.3. Trends
4. Summary and Conclusions
Supplementary Materials
Author Contributions
Funding
Data Availability Statement
Acknowledgments
Conflicts of Interest
References
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Percentage of Reaches | ||
---|---|---|
Stream Order 1 | Gaged Reaches | All Reaches |
1 | 9.2 | 48.8 |
2 | 19.2 | 21.7 |
3 | 26.9 | 12.1 |
4 | 23.9 | 6.9 |
5 | 12.3 | 4.1 |
6 | 6.0 | 3.7 |
7 | 1.5 | 1.9 |
8 | 0.9 | 0.9 |
Limitations of Existing Trend Assessments | Possible Directions to Expand Trend Assessments | Ways New Approach Could Enhance Understanding of Change and Processes Driving Change |
---|---|---|
Limited spatial extent. Existing studies are often limited in the number of sites or spatial extent over which they conduct trend assessments. | Analyze trends at a greater number of sites across the basin representative of different elevations, land uses (e.g., not just reference streams), and subbasins (e.g., Upper Green, Yampa-White, etc). | Trend analyses would include a basin-wide assessment of streamflow, including all sub-basins, tributaries, and reference sites, where possible. Additionally, having trend analyses at a denser spatial resolution will enable a more robust assessment of how and when streamflow changes in different UCOL subbasins. |
Limited scope. Heavy focus on streamflow conditions most relevant to spring runoff (high and mean flows). | Assess trends in additional metrics including magnitude, duration, and frequency of low-streamflow events and high and mean streamflow events during summer periods. | Summer precipitation (monsoons) are important for moderating water demand for agriculture and urban outdoor use. Likewise, monsoon events and characteristics of low-streamflow are important to ecological functions. |
Out of date. Current (2000–2021) temperature-driven drought is unprecedented in the gaged record. | Rapidly changing drivers of streamflow declines coupled with water demand exceeding supplies warrants regular updates to trend estimates. | Obtain a better understanding of the relationships among hydroclimatic and water use variables to improve water availability assessments. |
Limited trend attribution. Heavy emphasis on how hydroclimatic variables influence streamflow to the detriment of other potentially important drivers. | Expand trend attribution investigations to assess the influence of other attributes, including large scale land use change, changes in water use driven by irrigation methods or population increases, and changes in vegetation, to better understand drivers of change. | An enhanced understanding of processes driving streamflow trends will inform resource managers seeking to mitigate the impacts of drivers, where possible, on declining streamflow. |
Limitations/Gaps in Existing Trend Assessments | Possible Directions to Expand Trend Assessments | Ways New Approach Could Enhance Understanding of Change and Processes Driving Change |
---|---|---|
Limited spatial extent. Existing studies are often limited in the number of sites or spatial extent over which they conduct dissolved-solids trend assessments. In many cases, the number of sites where trends were analyzed is less than 20, often excluding sub-basins and tributary streams. | Analyze trends at a greater number of sites across the basin. Dissolved-solids concentrations and streamflow data exist across the basin and could be applied more broadly to assess spatial patterns in trends. | Trend analyses would include a basin-wide assessment of dissolved solids, including all sub-basins, tributaries, and reference sites, where possible. Additionally, having trend analyses at a denser spatial resolution will enable a more robust assessment of how and when dissolved-solids change in different UCOL sub-areas. |
Most studies report monotonic trends that provide no information about the patterns of dissolved-solids change through time. | Apply state-of-the-science trend evaluation methodology to estimate trend patterns through time. | Understanding the evolving patterns of how dissolved-solids change through time is useful for assessing drivers of change and understanding the changing rates of trends through time [114]. |
Trend assessments are out of date. | Automate analyses to update trends on an annual or seasonal basis so that trends are current and up-to-date. | A framework for providing up-to-date assessments of trend across the UCOL could help resource managers better understand changing water supplies and changing conditions in ecosystems. It would also provide an opportunity to continuously evaluate current conditions in the context of historical variability and long-term shifts. |
Many trend assessments apply trend estimation techniques with no descriptive capabilities, limiting the amount of information that can be obtained from collected water quality and streamflow data. | Apply new, state-of-the science tools such as WRTDS to obtain trend outputs that not only identify trends, but describe the nature, rate, magnitude, and significance of dissolved-solids change. | Tools such as WRTDS provide robust estimates of trends that remove the year-to-year influence of streamflow, describe the changing nature of dissolved solids, apply a flexible modeling framework that does not assume the data follow a particular form, and allow water quality and streamflow relationships to evolve through time [114]. |
Fixed trend periods. Many studies analyze trends between fixed starting/ending dates to meet specific study objectives. With updates to modeling and computing capabilities, trends could be modeled for any combination of trend periods provided adequate data are available. | Provide trends for all possible combinations of trend periods and make data visualization tools that allow for an adjustable time-period selection. | Trends for user-defined periods of interest allow trends to be more versatile and flexible to meet a range of resource manager and data user needs. |
Limited integration of dissolved-solids trends with other watershed parameters. In some cases, dissolved-solids trends are assessed in conjunction with changes in streamflow and/or major ions, but largely efforts to integrate dissolved-solids trends with other watershed variables is limited. | Integrate dissolved-solids trends with other priority water availability components and across a greater number of sites in the basin. | Integration of trends from multiple watershed variables could help to expand understanding of how water quality, streamflow, groundwater, and reservoir conditions interact and affect dissolved solids in the UCOL, enabling users to begin evaluating change in the system as a whole, not as an assortment of individual components. |
Most trends are generated on an annual basis. | Assess seasonal/monthly trends in dissolved solids, and/or trends during baseflow-dominated-seasons of the year. | Enhance understanding of seasonal changes in dissolved solids that could inform drivers of change. |
Trends are not compared to benchmarks. | Put trends in context of benchmarks relevant for a wide variety of water uses (ecosystem, municipal supply, irrigation, industrial uses, etc.). | Obtain a better understanding of whether dissolved solids are trending toward conditions of concern. |
Limited trend attribution. Several studies compare dissolved-solids trends to periods affected by watershed change (such as reservoir construction, salinity mitigation projects, mining, or other watershed activities), but a comprehensive assessment linking watershed changes to dissolved-solids trends has not been conducted. | Conduct a comprehensive trend attribution investigation to combine patterns of historical change in dissolved solids and watersheds attributes to better understand drivers of change. | An enhanced understanding of watershed processes driving dissolved-solids change will inform:
|
Limitations of Existing Trend Assessments | Possible Directions to Expand Trend Assessments | Ways New Approach Could Enhance Understanding of Change and Processes Driving Change |
---|---|---|
Limited spatial extent. Existing studies use estimated groundwater storage data. | Analyze trends at groundwater wells in the UCOL. | Trend analyses would include a basin-wide assessment of groundwater levels. Assessment of trends in groundwater levels could expand the spatial extent and inform changes in groundwater-surface water interaction. |
Out of date. Current (2000–2021) temperature-driven drought is unprecedented in the gaged record. | Rapidly changing drivers of groundwater level trends, including hydroclimatic variables and water management operations, warrant regular updates to trend estimates. | Obtain a better understanding of the relationships among drivers to improve water availability assessments. |
Limited trend attribution. Focus has mostly been on climate data. | Expand trend attribution investigations to assess the influence of anthropogenic factors, including groundwater withdrawals, especially during the recent drought period where groundwater withdrawals likely increased. | An enhanced understanding of processes driving river temperature trends could inform resource managers seeking to mitigate the impacts of drivers, where possible, on changing groundwater levels. |
Limitations of Existing Trend Assessments | Possible Directions to Expand Trend Assessments | Ways New Approach Could Enhance Understanding of Change and Processes Driving Change |
---|---|---|
Limited spatial extent. Existing studies are often conducted at a broad spatial scale. | Analyze trends at a greater number of sites (or area if using raster data) across the basin representative of different elevations, land uses, and subbasins (e.g., Upper Green, Yampa-White, etc). | Trend analyses could include a basin-wide assessment of snowpack and related climate metrics. Additionally, having trend analyses at a denser spatial resolution could enable a more robust assessment of how and when snowpack changes in different UCOL subbasins. |
Limited scope. Few snowpack metrics assessed at same time in existing studies. | Assess trends in multiple metrics (e.g., related to timing, total, precipitation). | Better understand how spatial variability across the basin, including differences in topography, elevation, and land use, influences trends in snowpack. |
Limited understanding of how trends in snowpack influence water availability, as influenced by water quality. | Expand trend investigations to assess the influence of changes in snowpack to changes in salinity. | An enhanced understanding of processes driving snowpack trends will inform resource managers seeking to mitigate the impacts of drivers, where possible, on salinity. |
Limitations of Existing Modeling Capabilities | Possible Directions to Improve Modeling Abilities | Ways Improvements Could Enhance Prediction |
---|---|---|
Scaling: large-scale models may be less accurate or neglect important processes at fine spatial scales yet small-scale models don’t provide information over larger areas necessary for basin-wide water availability assessments. | Include processes that are important at small scales in large-scale models as computational abilities improve, explore data-driven and hybrid approaches to prediction at a range of scales. | Improved prediction at a range of spatial scales. |
Separation between natural and human systems. Many models don’t represent both natural and human processes that affect water availability. | Integrate human systems including reservoirs, water use, diversions, water rights, land cover and use, and other human effects into hydrologic models. | Improve process understanding, relevance to land and water management, and applicability for near-term forecasting, long-term projections, and scenario-testing. |
Separation between water quantity and water quality modeling. | Integrate water quantity and quality models. | Provide a more comprehensive assessment of water availability for a wider range of water users. |
Separation between surface and subsurface systems. Although some models consider both, many do not. | Integrate surface and subsurface models. | Provide a more comprehensive assessment of water availability for a wider range of water users. Improve process-understanding and applicability for long-term projections and scenario-testing. |
Lack of process representation or data on key processes limits applicability of some models. While this may depend on the purpose of the model, lack of, or poor, process representation can reduce prediction accuracy. For data-driven models specifically, it can also reduce explainability. | Depending on the model purpose, add relevant processes or data representing processes. This could include improved representation of snowpack and groundwater-surface water interactions, and related processes. For data-driven models, consider methods to improve explainability. | Improved prediction accuracy, explainability, and relevance to near-term forecasting and long-term projections. |
Uncertainty about modeling approach. | Test multiple modeling approaches with common datasets to understand the effects of modeling decisions and representations. | Results would indicate how modeling decisions influence predictions and interpretation of results. |
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Tillman, F.D.; Day, N.K.; Miller, M.P.; Miller, O.L.; Rumsey, C.A.; Wise, D.R.; Longley, P.C.; McDonnell, M.C. 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. Water 2022, 14, 3813. https://doi.org/10.3390/w14233813
Tillman FD, Day NK, Miller MP, Miller OL, Rumsey CA, Wise DR, Longley PC, McDonnell MC. 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. Water. 2022; 14(23):3813. https://doi.org/10.3390/w14233813
Chicago/Turabian StyleTillman, Fred D, Natalie K. Day, Matthew P. Miller, Olivia L. Miller, Christine A. Rumsey, Daniel R. Wise, Patrick C. Longley, and Morgan C. McDonnell. 2022. "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" Water 14, no. 23: 3813. https://doi.org/10.3390/w14233813
APA StyleTillman, F. D., Day, N. K., Miller, M. P., Miller, O. L., Rumsey, C. A., Wise, D. R., Longley, P. C., & McDonnell, M. C. (2022). 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. Water, 14(23), 3813. https://doi.org/10.3390/w14233813