Columbia River Basin Forecast
2021 Long-Term Water Supply & Demand Forecast Data Access Website
State of Washington Department of Ecology · Washington State University · The University of Utah · Aspect Consulting · State of Washington Water Research Center
The purpose of this StoryMap is to provide access to the data underlying the results of the Columbia River Basin 202 Long-Term Water Supply and Demand Forecast. Specifically, this StoryMap will guide you through each figure within the 2021 Columbia River Basin Long-term Water Supply and Demand Forecast Legislative Report (Hall et al. 2022) and will allow you to download the figure’s image file and the associated data used to develop that figure. However, this StoryMap does not discuss how results were obtained or how to interpret these results. For a description of the Forecast’s analysis and a discussion of its findings, see the following documents:
From left to right: the 2021 Legislative Report , the flyer , and the 2021 Technical Supplement for the Columbia River Basin Long-Term Water Supply & Demand Forecast.
In addition, for a compressed folder with the image files for all figures within the Legislative Report, click here .
The StoryMap follows the structure of the Legislative Report and is organized using similar, shortened headings. To skip to the figures in a particular section of the Report, use the navigation bar at the top to select the appropriate report heading. Alternatively, you may scroll through to view the figures in the order they appear in the Legislative Report.
Data-based figures will have one or multiple links that allow you to download the associated data. Some figures may offer multiple links if different types of data are available. In such cases, the data links are described according to the type of data they contain (e.g. “spatial” data will contain shapefiles or some other spatial data type). To download spatial data, you must create a free ArcGIS online account if you do not already have one. To ensure the best viewing experience, you must be using one of the following browsers: Google Chrome, Mozilla Firefox, Safari 3 and later, or Microsoft Edge. If there are any issues viewing the StoryMap or the associated figures and data, first try updating your browser to the latest version. If problems persist, please contact aaron.whittemore@wsu.edu.
This data access website is not fully ADA accessible due to limitations with the platform. For ADA accessible versions of the figures, please contact the Washington State Department of Ecology. The Department of Ecology is committed to providing people with disabilities access to information and services by meeting or exceeding the requirements of the Americans with Disabilities Act (ADA), Section 504 and 508 of the Rehabilitation Act, and Washington State Policy #188. To request an ADA accommodation, contact Ecology by phone at 509-454-4241 or email at tim.poppleton@ecy.wa.gov . For Washington Relay Service or TTY call 711 or 877-833-6341. Visit Ecology’s website for more information.
Meeting Eastern Washington's Water Needs
Figure 1. Expected changes that will influence future water supplies and demands
Figure 1. Expected changes that will influence future water supplies and demands. These expected trends inform the scenarios explored in this 2021 Forecast.
Figure 2. Integration of biophysical modeling with economic and policy modeling
Figure 2. Integration of biophysical modeling (surface water supply, crop dynamics and climate) with economic and policy modeling. The bottom panel highlights key improvements made in this 2021 Forecast.
Overview of Forecast Methods
Figure 3. Forecast results are provided for four different geographic scopes
Figure 3. Long-term water supplies and demands were forecast through 2040 and beyond, and results are provided for four different geographic scopes: Columbia River Basin, Washington’s Watersheds, Washington’s Aquifers, and the Columbia River Mainstem.
Figure 4. Biophysical modeling framework used in the forecast
Figure 4. Biophysical modeling framework for forecasting surface water supply and agricultural water demand across the Columbia River Basin. The diagram represents the basic modeling framework used since the 2011 Forecast. The diagram is accompanied by brief descriptions of each modeling component (Panels A, B, and C), and highlights of key improvements made in this 2021 Forecast.
Figure 5. Projects funded by the Office of Columbia River
Figure 6. Estimated proportions of different crops in Washington
Figure 6. Estimated proportions of different crops in Washington, used as inputs to the integrated modeling of agricultural water demand (left) and irrigated acres of certain crop groups of particular interest for this analysis (right). The historical (2020) crop mix was estimated using USDA NASS survey data, and the 2040 crop mix was estimated based on a statistical analysis of trends in different crops between 1999 and 2019.
Figure 7. Greenness cycles for a single cropping system and a double-cropped system
Figure 7. Schematic of greenness cycles for a single-cropping system (left) and for a double-cropped system (right). These curves were obtained from time series of Enhanced Vegetation Index (EVI) obtained from Sentinel-2 optical data.
Figure 8. Diagram representing a well pumping groundwater in eastern Washington
Figure 8. Diagrams representing a well pumping groundwater in eastern Washington (right), and the four main basalt aquifer layers of the Columbia Plateau Regional Aquifer System (CPRAS), with examples of how wells access those aquifer layers (right). The data used in the trend analysis represent the spring high water level, and trends were summarized within each aquifer layer (that is, using wells that access the same aquifer layer, shown by the color of the downturned triangle beside each well). The vulnerability assessment is based on the available saturated thickness.
Water Supply and Demand for the Columbia River Basin
Figure 9. The Columbia River Basin geographic scope
Figure 9. The Columbia River Basin geographic scope.
Figure 10. Expected changes in timing of water supplies by 2040
Figure 10. Expected change by 2040 in timing of water supply in the Columbia River Basin. The water supply timing in the historical (1986- 2015) and forecast (2040) time periods was calculated using a center of timing approach, and was quantified at Bonneville Dam. Historical supply for a median (50th percentile) supply year is shown in the black line, and the range of possible future (2040) supplies under different greenhouse gas emissions scenarios are shown in the blue and green shading (for further details see caption in Figure 12). Historical and future center of timing dates are shown in the blue and brown lines, respectively. Future center of timing date is the median value of all 34 climate change scenarios.
Figure 11. Surface water supply and agricultural water demand across the entire Columbia River Basin
Figure 11. Comparison of regulated surface water supply and agricultural water demands for the historical (1986-2015; top panel) and forecast (two future time periods: 2040 in the middle panel; 2070 in the bottom panel) periods across the entire Columbia River Basin, including portions of the basin outside of Washington State. Interannual variability (20th and 80th percentile conditions around the median year values) is shown for both supply (dotted lines) and demand (error bars). In the 2040 and 2070 forecast panels, all values represent the median of 34 different climate scenarios (see Box 4 for details).
Figure 12. Expected change by 2040 in surface water flows where rivers enter Washington State
Figure 12. Expected change by 2040 in surface water supplies for major Columbia River tributaries entering Washington State (values measured just upstream of the point where the rivers enter Washington). The top number for each tributary refers to change expected by 2040 during high (80th percentile) supply years; the middle number refers to change expected by 2040 during median (50th percentile) supply years. The bottom number refers to change expected by 2040 during low (20th percentile) supply years. The confidence interval around the average change quantifies the uncertainty in possible future change, determined by the 34 climate change scenarios considered. All values are in cubic feet per second. Changes highlighted in orange and blue are decreases and increases in supply (expected to be associated with decreasing and increasing water availability), respectively, that are statistically different to zero. Values in black show metrics that are expected to remain mostly stable into the future. Inset panels show the historical (1986-2015) and forecast (2040) regulated surface water supplies (in thousands of acre-feet per month) on the Snake and Columbia Rivers upstream of the point where they enter Washington State for low (20th percentile; bottom graph in each inset panel), median (50th percentile; middle graph in each inset panel), and high (80th percentile; top graph in each inset panel) supply years. The spread of forecast (2040) supply is due to the range of climate change scenarios considered.
Snake River Regulated Surface Water Supply
Columbia River Regulated Surface Water Supply
Figure 13. Expected change in agricultural water demand by 2040
Figure 13. Expected change by 2040 in timing of agricultural water demand in the Columbia River Basin. The timing of water demand in the historical (1986-2015) and forecast (2040) time periods was calculated using a center of timing approach, and was quantified at Bonneville Dam. Historical agricultural water demand for a median (50th percentile) demand year is shown in the black line, and the range of possible future (2040) demands under different greenhouse gas emissions scenarios (using historical planting dates and historical crop mix) are shown in the two tones of orange shading. Historical and future center of timing dates are shown in the black and crimson lines, respectively. Future center of timing date is the median value of all 34 climate change scenarios.
Figure 14. Cropping intensity of irrigated crops by county, across five states
Figure 14. Cropping intensity—the ratio of total harvested irrigated acres to irrigated extent—of irrigated crops by county, averaged over the last four waves of the Census of Agriculture (USDA NASS: 2002, 2007, 2012, and 2017).
Figure 15. Washington's net electricity generation by source
Figure 15. Washington’s net electricity generation by source, produced by the Energy Information Administration in January 2021. Available online at https://www.eia.gov/state/?sid=WA#tabs-4 , accessed May 18, 2021.
Water Supply and Demand for Washington's Watersheds
Figure 16. Washington's watersheds geographic scopes, with WRIAs and county boundaries
Figure 16. Washington’s Watersheds geographic scope: Water Resource Inventory Areas (WRIAs) in eastern Washington, and their relation to county boundaries.
Figure 17. Expected change by 2040 in surface water flows in tributaries
Figure 17. Expected change by 2040 in surface water flows (prior to accounting for demands) where tributaries join Washington’s Columbia River Mainstem (above Bonneville Dam). The three numbers for each river refer to forecast (2040) surface water supply for a high (80th percentile; top), median (50th percentile; middle) and low supply year (20th percentile; bottom), averaged across 34 climate change scenarios (confidence interval around that average in parentheses). Changes highlighted in orange and blue are decreases and increases in supply (expected to be associated with decreasing and increasing water availability), respectively, that are statistically different to zero. All values are in cubic feet per second.
Figure 18. Changes in timing of water supply expected during high flow years by 2040
Figure 18. Changes in the timing of water supply expected during high flow years (80th percentile) by 2040. We quantified the shift based on the change, in number of days, of the center of timing of supply from the historical (1986-2015) to the forecast (2040) period (using the median of 34 climate change scenarios). Note that one value is given for WRIAs 37, 38 and 39, and one value is given for WRIAs 44 and 50, reflecting the sum of changes in those groups of WRIAs.
Figure 19. Historical Snowmelt Ratio
Figure 19. Historical (1976-2005) snowmelt ratio, obtained from an independent dataset. The snowmelt ratio reflects the relative contributions of snowmelt and rainfall to streamflow. The higher the ratio, the greater the contribution from snowmelt.
Figure 20. Changes in annual water supply expected during high flow years by 2040
Figure 20. Changes in annual water supply expected during high flow years (80th percentile) by 2040, in thousands of acre-feet. WRIAs are colored based on the magnitude of change in annual water supply between historical (1986-2015) and forecast (2026-2055) time periods. Future supplies were represented by the median of 34 climate change scenarios. Note that one value is given for WRIAs 37, 38 and 39, reflecting the sum of changes in those WRIAs.
Figure 21. Changes in annual water supply expected during low flow years by 2040
Figure 21. Changes in annual water supply expected during low flow years (20th percentile) by 2040, in thousands of acre-feet. WRIAs are colored based on the magnitude of change in annual water supply between historical (1986-2015) and forecast (2026-2055) time periods. Future supplies were represented by the median of 34 climate change scenarios. Note that one value is given for WRIAs 37, 38 and 39, and one value is given for WRIAs 44 and 50, reflecting the sum of changes in those groups of WRIAs.
Figure 22. Historical agricultural water demands across eastern Washington's WRIAs
Figure 22. Historical (1986-2015) agricultural water demands across eastern Washington’s Water Resource Inventory Areas (WRIAs). Demand is expressed in acre-feet per year.
Figure 23. Expected change in agricultural water demand by 2040, across WRIAs
Figure 23. Expected change in agricultural water demand between the historical (1986-2015) and forecast (2040) time periods, summarized by WRIA. Changes in demand are expressed in acre-feet per year.
Figure 24. Total annual residential water demands for 2040 for counties and municipalities
Figure 24. Total annual residential water demands for 2040 for domestic users (shaded areas) and municipalities (yellow circles).
Figure 25. Expected change in total annual residential consumptive water use by 2040
Figure 25. Change in total annual residential consumptive water use from 2020 to 2040, expressed as a percent of 2020 use, summarized by WRIA.
Figure 26. Expected change in residential consumptive water use during summer months by 2040
Figure 26. Change in residential consumptive water use during summer months (June, July and August) from 2020 to 2040, summarized by WRIA.
Figure 27. Expected change in surface water supply during summer months by 2040
Figure 27. Change in surface water supply during summer months (June, July and August) from historical (1986-2015) to forecast (2040) periods, by WRIA. Note that one value is given for WRIAs 37, 38 and 39, and one value is given for WRIAs 44 and 50, reflecting the sum of changes in those groups of WRIAs.
Figure 28. Percent of available water rights used by 2040 for sampled water provider systems
Figure 28. Percent of available water rights used by 2040 for sampled water provider systems.
Figure 29. Historical annual minimum low flows - 7Q10
Figure 29. Historical (1982-2011) annual minimum 7-day average streamflow with a 10-year recurrence interval (7Q10) across Washington State’s WRIAs. Map produced for this 2021 Forecast using data obtained from Mauger et al. (2021).
Figure 30. Expected changes in annual minimum low flows - 7Q10
Figure 30. Expected changes in annual minimum 7-day average streamflow with a 10-year recurrence interval (7Q10) across Washington State’s WRIAs, between the historical (1982-2011) and the projected future (2030-2059) time periods. Future projections summarize results from 12 climate change scenarios, developed using dynamic downscaling, under greenhouse gas emissions scenario RCP 8.5. Map produced for this 2021 Forecast using data obtained from Mauger et al. (2021).
Figure 31. Historical annual minimum low flows - 7Q2
Figure 31. Historical (1982-2011) annual minimum 7-day average streamflow with a 2-year recurrence interval (7Q2) across Washington State’s WRIAs. Map produced for this 2021 Forecast using data obtained from Mauger et al. (2021).
Figure 32. Expected changes in annual minimum low flows - 7Q2
Figure 32. Expected changes in annual minimum 7-day average streamflow with a 2-year recurrence interval (7Q2) across Washington State’s WRIAs, between the historical (1982-2011) and the projected future (2030-2059) time periods. Future projections summarize results from 12 climate change scenarios, developed using dynamic downscaling, under greenhouse gas emissions scenario RCP 8.5. Map produced for this 2021 Forecast using data obtained from Mauger et al. (2021).
Figure 33. Expected change in curtailment frequency in two WRIAs
Figure 33. Change in expected curtailment frequency between historical (1986-2015) and forecast (2040) time periods in the Wenatchee watershed (WRIA 45; left panel) and the Methow watershed (WRIA 48; right panel), expressed as the additional number of years, out of 30 years, when curtailment occurs. Results for each watershed are shown for two different greenhouse gas emissions scenarios (RCP 4.5 and RCP 8.5) and reflect the median change expected when 17 climate change scenarios are explored under each emissions scenario. Curtailment frequency was calculated on a weekly basis. Values above the zero line reflect increases in curtailment frequency (brown arrow), and values below the zero line reflect decreases in frequency (blue arrow).
Figure 34. Expected change in yield due to reduced irrigation in the Yakima Basin
Figure 34. Change in yield due to reduced irrigation under historical (1986-2015) and future (2040) climate conditions in the Yakima (WRIAs 37, 38, 39). Changes in yields under future conditions are calculated under two alternative greenhouse gas emissions scenarios (RCPs 4.5 and 8.5). Forage includes alfalfa hay and grass hay. High value annuals include onions, potatoes, mint, sweet corn, carrots, oats, dill, grass seed, sunflower, sugar beets, pepper, canola, and yellow mustard. High Value Perennials include blueberries, apples, cherries, peaches, pears, grapes and hops. Other field crops include wheat, peas, barley, corn, and dry beans (for more details see the Forecast Results for Individual WRIAs section).
Water Supply Forecast for Washington's Aquifers
Figure 35. Washington's aquifers geographic scope, showing the distribution of well locations
Figure 35. Washington’s Aquifers geographic scope, showing the distribution of well locations (circles) used in the groundwater trends analysis. The colors of each well location show which aquifer layer the well accesses if within the Columbia Plateau Regional Aquifer System (CPRAS), or whether the well accesses a source of groundwater outside of the CPRAS.
Figure 36. Interpolated trends in groundwater levels in the Grande Ronde Aquifer Layer
Figure 36. Interpolated trends in groundwater levels in the Grande Ronde Aquifer Layer. Interpolations were completed within each individual subarea based on a minimum of three wells (for further details see the Grande Ronde pages in the Forecast Results for Aquifer Layers section). Areas that do not have interpolated shading lacked adequate data to complete the analysis. The trends are overlaid on a satellite map where cultivated land area is visible in darker green for the central and southern subareas.
Figure 37. Interpolated trends in groundwater levels in the Wanapum Aquifer Layer
Figure 37. Interpolated trends in groundwater levels in the Wanapum Aquifer Layer. Interpolations were completed within each individual subarea based on a minimum of three wells (for further details see the Wanapum pages in the Forecast Results for Aquifer Layers section). Areas that do not have interpolated shading lacked adequate data to complete the analysis. The trends are overlaid on a satellite map where cultivated land area is visible in darker green for the central and southern subareas
Figure 38. Time until the available saturated thickness has declined by 25% in at least one aquifer layer
Figure 38. Time (in years) until the average available saturated thickness has declined by 25% in at least one aquifer layer in each groundwater subarea. These times are based on declines in available saturated thickness in different aquifer layers, as we show the most vulnerable aquifer layer for each subarea; that is, the time until 25% decline in available saturated thickness may reflect the vulnerability related to declines in the Grande Ronde layer for some subareas, for the Wanapum layer for other subareas, and the Overburden layer for other subareas (for more details see the Forecast Results for Aquifer Layers section).
Water Supply and Demand for Washington's Columbia River Mainstem
Figure 39. Washington's Columbia River Mainstem geographic scope
Figure 39. Washington’s Columbia River Mainstem geographic scope.
Figure 40. Regulated surface water supply along the Columbia River mainstem
Figure 40. Historical (1986-2015: left column) and forecast (2040: center column; and 2070: right column) regulated surface water supply at Priest Rapids (top row), McNary (center row) and Bonneville (bottom row) Dams for low (20th percentile), median (50th percentile), and high (80th percentile) supply years, averaged across 34 climate change scenarios. Supplies presented are prior to accounting for out-of-stream demands. Also shown are the Washington State instream flow (WA ISF) and federal Biological Opinion (BiOp) flow targets (bars).
Figure 41.
Figure 41. Modeled historical (1986-2015) frequency of instream flow deficits (quantified as the number of years out of 30 years) at nine locations along the Columbia River Mainstem. The frequency of instream flow deficits was calculated on a weekly basis. These estimates were not conditional on whether the threshold of expected supply that would trigger curtailment decisions on the Mainstem (March through September supply forecast on March 1 to be less than 60 million acre-feet at The Dalles Dam) was reached.
Figure 42. Expected change in frequency of instream flow deficits along the Columbia River Mainstem
Chief Joseph Dam (left), Wells Dam (middle), Rocky Reach Dam (right)
Rock Island Dam (left), Wanapum Dam (middle), Priest Rapids Dam (right)
McNary Dam (left), John Day Dam (middle), The Dalles (right) Figure 42. Change in expected frequency of instream flow deficits (quantified as the difference in number of years out of 30 years) between historical (1986-2015) and forecast (2040) time periods at nine locations along the Columbia River Mainstem. Results are shown for two different greenhouse gas emissions scenarios (RCP 4.5 and RCP 8.5) and reflect the median change expected when 17 climate change scenarios are explored under each emissions scenario. The frequency of instream flow deficits was calculated on a weekly basis.
Forecast Results for Individual WRIAs
Below is a map of eastern Washington's WRIAs. Users can either click on a WRIA within the map or scroll down the left-side panel to explore a specific WRIA in more detail. Upon navigating to a WRIA, clicking on the "Figures and Data" link will allow users to explore all the figures on the given WRIA's pages in the legislative report. Beneath the captions of these figures will be links to their underlying data.
WRIA 45 - Wenatchee
Figures and Data
WRIA 46 - Entiat
Figures and Data
WRIA 47 - Chelan
Figures and Data
WRIA 48 - Methow
Figures and Data
WRIA 49 - Okanogan
Figures and Data
WRIA 50 - Foster
Figures and Data
WRIA 51 - Nespelem
Figures and Data
WRIA 52 - Sanpoil
Figures and Data
WRIA 53 - Lower Lake Roosevelt
Figures and Data
WRIA 54 - Lower Spokane
Figures and Data
WRIA 55 - Little Spokane
Figures and Data
WRIA 56 - Hangman
Figures and Data
WRIA 57 - Middle Spokane
Figures and Data
WRIA 58 - Middle Lake Roosevelt
Figures and Data
WRIA 59 - Colville
Figures and Data
WRIA 60 - Kettle
Figures and Data
WRIA 61 - Upper Lake Roosevelt
Figures and Data
WRIA 62 - Pend Oreille
Figures and Data
Forecast Results for Aquifer Layers
Below are the figures within the aquifer pages of the legislative report. Beneath the caption of each figure is a link to download the underlying data associated with that figure.
Grande Ronde Aquifer Layer
Summary of the Overall Trends by subarea in the Grande Ronde Aquifer Layer. The black lines represent the median trend for each subarea. The bottom and top of each box represents the 25th and 75th percentiles, respectively. The dashed lines terminate in the most extreme lower and upper values that are not considered outliers. Outliers are represented by asterisks. A minimum of three wells within each subarea was required such that missing boxes represent subareas with two or fewer wells within them. The horizontal red line marks the zero trendline, where values above represent increasing water levels and values below it show decreasing water levels.
Interpolated trends in groundwater levels in the Grande Ronde Aquifer Layer. Interpolations were completed within each individual subarea based on a minimum of three wells in the subarea. Inverse-distance weighting with a radius of six miles was used for the interpolation. Areas that do not have interpolated shading indicate regions without adequate data to complete the analysis. The trends are overlaid on a satellite map where cultivated land area is visible in darker green for the central and southern subareas.
Map A shows the average percent change in available saturated thickness between 2020 and 2040. Map B shows the number of years until the average available saturated thickness has declined by 25%. The values and methodological details are listed in the vulnerability table, above.
Wanapum Aquifer Layer
Summary of the Overall Trends by subarea in the Wanapum Layer. The black lines represent the median trend for each subarea. The bottom and top of each box represents the 25th and 75th percentiles, respectively. The dashed lines terminate in the most extreme lower and upper values that are not considered outliers. Outliers are represented by asterisks. A minimum of three wells within each subarea was required such that missing boxes represent subareas with two or fewer wells within them. The horizontal red line marks the zero trendline, where values above represent increasing water levels and values below it show decreasing water levels.
Interpolated trends in groundwater levels in the Wanapum Aquifer Layer. Interpolations were completed within each individual subarea based on a minimum of three wells in the subarea. Inverse-distance weighting with a radius of six miles was used for the interpolation. Areas that do not have interpolated shading indicate regions without adequate data to complete the analysis. The trends are overlaid on a satellite map where cultivated land area is visible in darker green for the central and southern subareas.
Map A shows the average percent change in available saturated thickness between 2020 and 2040. Map B shows the number of years until the average available saturated thickness has declined by 25%. The values and methodological details are listed in the vulnerability table, above.
Saddle Mountain Aquifer Layer
Summary of the Overall Trends by subarea in the Saddle Mountain Aquifer Layer. The black lines represent the median trend for each subarea. The bottom and top of each box represents the 25th and 75th percentiles, respectively. The dashed lines terminate in the most extreme lower and upper values that are not considered outliers. Outliers are represented by asterisks. A minimum of three wells within each subarea was required such that missing boxes represent subareas with two or fewer wells within them. The horizontal red line marks the zero trendline, where values above represent increasing water levels and values below it show decreasing water levels.
Interpolated trends in groundwater levels in the Saddle Mountain Aquifer Layer. Interpolations were completed within each individual subarea based on a minimum of three wells in the subarea. Inverse-distance weighting with a radius of six miles was used for the interpolation. Areas that do not have interpolated shading indicate regions without adequate data to complete the analysis. The trends are overlaid on a satellite map where cultivated land area is visible in darker green for the central and southern subareas.
Map A shows the average percent change in available saturated thickness between 2020 and 2040. Map B shows the number of years until the average available saturated thickness has declined by 25%. The values and methodological details are listed in the vulnerability table, above.
Overburden Aquifer Layer
Summary of the Overall Trends by subarea in the Overburden Aquifer Layer. The black lines represent the median trend for each subarea. The bottom and top of each box represents the 25th and 75th percentiles, respectively. The dashed lines terminate in the most extreme lower and upper values that are not considered outliers. Outliers are represented by asterisks. A minimum of three wells within each subarea was required such that missing boxes represent subareas with two or fewer wells within them. The horizontal red line marks the zero trendline, where values above represent increasing water levels and values below it show decreasing water levels.
Interpolated trends in groundwater levels in the Overburden Aquifer Layer. Interpolations were completed within each individual subarea based on a minimum of three wells in the subarea. Inverse-distance weighting with a radius of six miles was used for the interpolation. Areas that do not have interpolated shading indicate regions without adequate data to complete the analysis. The trends are overlaid on a satellite map where cultivated land area is visible in darker green for the central and southern subareas.
Map A shows the average percent change in available saturated thickness between 2020 and 2040. Map B shows the number of years until the average available saturated thickness has declined by 25%. The values and methodological details are listed in the vulnerability table, above.
Outside CPRAS
Summary of the Overall Trends by subarea in the Outside CPRAS. The black lines represent the median trend for each subarea. The bottom and top of each box represents the 25th and 75th percentiles, respectively. The dashed lines terminate in the most extreme lower and upper values that are not considered outliers. Outliers are represented by asterisks. A minimum of three wells within each subarea was required such that missing boxes represent subareas with two or fewer wells within them. The horizontal red line marks the zero trendline, where values above represent increasing water levels and values below it show decreasing water levels.
Interpolated trends in groundwater levels Outside CPRAS. Interpolations were completed within each individual subarea based on a minimum of three wells in the subarea. Inverse-distance weighting with a radius of six miles was used for the interpolation. Areas that do not have interpolated shading indicate regions without adequate data to complete the analysis. The trends are overlaid on a satellite map where cultivated land area is visible in darker green for the central and southern subareas.
Map A shows the average percent change in available saturated thickness between 2020 and 2040. Map B shows the number of years until the average available saturated thickness has declined by 25%. The values and methodological details are listed in the vulnerability table, above.
