Data and tools

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This section of the Colorado River Science Wiki automatically collates all of the information found under the Data and tools headings on every page in the Science and applications section, and lists those datasets and tools below in the same order as the the pages in the Science and applications section.

Climate patterns and variability

NOAA NCEI Climate at a Glance

The “CAG” tool is a versatile tool that can be used to generate many types of charts, maps, and analyses from NOAA’s official nClimGrid monthly gridded climate dataset. Selecting "Regional" and "Time series" at top brings up several dozen region options, including the Upper Basin and Lower Basin. Selecting "Regional" and "Mapping" allows data to be mapped with river basin boundaries.

Climate Toolbox - Historical Climograph

This tool, developed by researchers at the U. of California-Merced and partners, generates climographs of average (1981-2010) monthly temperature and precipitation for any point, county, HUC8 watershed, or user-selected area, from the gridMET gridded (4 km) climate dataset.

Recent climate change

NOAA NCEI Climate at a Glance - Regional Time Series

The “CAG” tool is a versatile tool that can be used to generate many types of charts, maps, and analyses from NOAA’s official nClimGrid monthly gridded (5 km) climate dataset. The link above opens the Regional and Time Series options, allowing users to plot temperature, precipitation, and other variables for the Upper Basin, Lower Basin, or many other U.S. basins and regions. All variables can be plotted from 1895 to present.

Climate Toolbox - Historical Climate Tracker

This tool, developed by researchers at the U. of California-Merced and partners, generates time series plots for any point, county, HUC8 watershed, or user-selected area from the gridMET gridded (4 km) climate dataset. Many more variables are available from gridMET than from NOAA's nClimGrid; however, gridMET only extends back to 1979. Some drought-related variables calculated from other climate datasets are available through this tool.

Weather and climate monitoring

Weather station data


This site created by the University of Utah provides map-based access to 1000s of observations from the NWS and FAA (ASOS/AWOS) automated networks, RAWS, SNOTEL, APRSWXNET/CWOP (citizen weather stations), and many other networks. Very useful for real-time monitoring of temperature, winds, humidity, and recent precipitation; users can also access historical observations.

ACIS Climate Maps (HPRCC)

These maps, generated from weather station observations from the NWS COOP network and updated daily, are very helpful for monitoring conditions from weekly to annual timescales. Note that the "shaded" maps are created using a very simple interpolation, unlike that used for gridded climate products.

Gridded climate products

NOAA NCEI Climate at a Glance

This versatile tool can be used to generate many types of charts, maps, and analyses from NOAA’s official nClimGrid gridded climate dataset, updated monthly.

Climate Toolbox

This toolset, developed by researchers at the U. of California-Merced and partners, generates many different types of charts and analyses from the gridMET gridded (4 km) climate dataset, updated daily.

WestWide Drought Tracker

These maps display the PRISM gridded climate product, updated monthly, for climate (temperature, precipitation) variables as well as drought indices (PDSI, SPI, SPEI). The "Percentile" maps show how unusual recent conditions are relative to the historical record.

Weather and climate forecasts

Weather Forecasts

NWS Homepage (access to all local forecasts)

The National Weather Service (NWS) homepage has a national map that, on-click, opens up the homepage for that local Weather Forecast Office, which has a region map that on-click brings up the NWS official local weather forecasts (nowcast to 7-day) and any hazard watches/warnings.

NWS National Digital Forecast Map

This interactive map presents a seamless mosaic of all of the local forecasts (out to 7 days) issued by the Weather Forecast Offices across the U.S., for temperature, precipitation, and several dozen other variables.

NWS WPC Quantitative Precipitation Forecast (QPF)

QPFs are specific forecasts of the most likely precipitation amounts over the next 1-7 days, issued as national maps. QPFs are used as inputs to the CBRFC's streamflow forecasts made on both short-term (10-day) and seasonal timescales. The NWS WPC QPF is based on guidance from several different weather models.

CBRFC Quantitative Precipitation Forecast (QPF) Grids

This is the QPF as used by CBRFC to drive their streamflow forecast model system. Days 2-7 are taken from the NWS WPC QPF product shown above; Day 1 comes from the very similar NWS National Blend of Models (NBM) QPF.

GEFS Ensemble Plumes (for cumulative precipitation)

This is another way of displaying a QPF (here, an 8-day ensemble forecast from the GFS weather model), for a single location. This URL shows the forecasted cumulative precipitation for KASE (Aspen, CO); zoom in on the map to select any other of ~20 locations within the Colorado River Basin. The plume shows the uncertainty in the forecast given our imperfect knowledge about the initial atmospheric conditions.

NWS CPC 8-14 day Temperature and Precipitation Outlooks

Because the skill of weather forecasts for beyond 7 days out is much lower, the official NWS "week 2" (8-14-day) forecasts are issued (daily) as probabilistic outlooks, indicating enhanced likelihoods that conditions over that period will fall into the 3 categories of above normal (upper 1/3), near-normal (middle 1/3), or below normal (lower 1/3 of all historical observations). Monthly and seasonal outlooks also use these "tercile" categories.

Sub-seasonal Climate Forecasts

NWS CPC Week 3-4 Temperature and Precipitation Outlooks

These "Week 3-4" outlooks (i.e., for the period 15-30 days after the forecast date) are issued weekly and show enhanced likelihoods that conditions for the forecast period will be in one of 2 categories: above or below the historical median. The Temperature outlook is an official forecast product, but the Precipitation outlook is still considered "experimental" due to low skill/reliability.

NWS CPC 1-month Temperature and Precipitation Outlooks

These monthly outlooks are issued for each full month (January, February, etc.) at two lead times: 0.5 months lead (i.e, issued in middle of prior month) and zero lead (end of prior month). Not surprisingly, the zero-lead monthly outlooks are more skillful since they incorporate short-term weather (0-14 days) forecast guidance, in addition to longer term guidance (equivalent to the Week 3-4 outlooks).

S2S Climate Outlooks for Watersheds

This interactive web tool, developed by NCAR and Reclamation, presents specific ("deterministic") forecasts of temperature and precipitation anomalies (departures from normal) from several weather/climate models, which can be viewed individually or as an 7-model ensemble ("NMME") average. These models are used as guidance for the NWS sub-seasonal outlooks listed above. The sub-seasonal forecasts available are for weeks 2-3 and 3-4 (CFSv2 only); and 1-month (all NMME models), at three lead times: zero, 1 month, and 2 months; the seasonal forecasts available are for 3-month seasons at three lead times: zero, 1 month, and 2 months.

Seasonal Climate Forecasts

NWS CPC Seasonal (3-month) Temperature and Precipitation Outlooks

These seasonal outlooks are issued monthly for overlapping 3-month periods (Jan-Mar, Feb-April, etc.) at lead times ranging from 0.5 months to 12.5 months. The shorter-lead outlooks are generally more skillful, but skill is relatively low for precipitation at all lead times. As with the CPC 8-14 day outlooks, the seasonal outlooks are probabilistic and based on 3 categories (above normal, near-normal, and below normal).

Projected future climate

The Climate Explorer

The Climate Explorer interactive tool (developed by NOAA and its partners) allows users to generate zoomable climate change maps for temperature and precipitation for the U.S. and northern Mexico, and time-series plots of projected future temperature and precipitation for U.S. counties. Other areas for analysis, such as river basin, cannot be selected. All projected climate data are from the LOCA-downscaled CMIP5 dataset (32 models).

Climate Toolbox

The Climate Toolbox is a diverse set of interactive tools developed by researchers at U. Cal-Merced and partners. All projected climate data are from the MACA-downscaled CMIP5 dataset (20 models).

Climate Toolbox - Climate Mapper

The Climate Mapper tool allows users to generate zoomable climate change maps for temperature as well as precipitation and a broad set of drought, agricultural, and fire-risk indicators. To access the projections, "Future: Projections" must be selected under Choose Data - Time Scale in the upper left. Projected climate data are from the MACA-downscaled CMIP5 dataset (20 models).

Climate Toolbox - Future Time Series

The Future Time Series tool allows users to generate time series for temperature as well as precipitation and a broad set of drought, agricultural, and fire-risk indicators. To access the projections, "Future: Projections" must be selected under Choose Data - Time Scale in the upper left. Projected climate data are from the MACA-downscaled CMIP5 dataset (20 models).

National Climate Change Viewer

The National Climate Change Viewer (NCCV) is a versatile interactive viewer developed by USGS. It allows users to generate zoomable change maps, time series, monthly climographs, and scatterplots for multiple climate variables. This viewer's analysis areas are river basins/watersheds (HUC2, HUC4, and HUC8); a separate viewer allows analyses by state or county. All projected climate data are from the MACA-downscaled CMIP5 dataset (20 models), same as for the Climate Toolbox.


SNOTEL and other in-situ snow data

NRCS Interactive Map

This very versatile tool provides a clear spatial overview of snowpack (SNOTEL) and other hydroclimate conditions across the western U.S., while allowing users to easily drill down into site-level data. Displays both near-real-time data (previous day) and historical data.

NRCS State Snow Survey Snow Products

The NRCS state snow survey sites provide many additional options--varying by state-- for viewing current and historical SNOTEL and snow course data, including monthly summary reports (Basin Outlook Reports).

CBRFC Snow Groups

Provides current year's time-series plots of SNOTEL SWE averaged across multiple SNOTEL sites (“snow groups”) selected to represent a particular catchment or area; ~300 options for catchments within the Colorado River Basin and eastern Great Basin.

CoCoRaHS Interactive Map

Provides daily new snow depth and SWE, and snow depth and SWE on the ground, from the hundreds of volunteer CoCoRaHS observers in the basin. Select Map Options > What to map these snow variables.

Gridded and modeled snow products

NOAA NOHRSC - SNODAS Interactive Map

Provides access to SNODAS daily gridded SWE and other snow variables; the SNODAS model builds and maintains a snowpack based on weather data and also assimilates SNOTEL data.

SnowView – Snow-Water Artificial Neural Network modeling system (SWANN)

This tool, developed at the U. of Arizona, shows a daily gridded snow dataset (SWANN) that uses snow models, assimilated SNOTEL data, and machine-learning methods. Users can compare SWANN with SNODAS for a catchment of interest.

CBRFC Modeled Snowpack – Interactive Conditions Map

Interactive map that provides daily-updated modeled SWE for ~500 catchment-elevation zones in the Colorado River Basin and eastern Great Basin. These modeled SWE data are used as key inputs for CBRFC's seasonal streamflow forecasts.

Other snowpack information

Colorado Dust-on-Snow (CODOS) reports

The CODOS program at the Center for Snow and Avalanche Studies (CSAS) tracks the deposition and emergence of dust layers in the snowpack, and snowpack temperature and other metrics, at 11 mountain pass locations throughout Colorado.

Soil moisture

Observational Data

NRCS SNOTEL/SCAN (current conditions, 20 in. depth)

A subset of the NRCS SNOTEL and SCAN stations are equipped with soil moisture sensors. The NRCS Interactive Map allows users to view current conditions at each station by selecting the desired measurement (e.g., soil moisture value at 20 in. depths). Navigate to individual stations to access data on previous soil moisture conditions.

Modeled Data

Colorado River Basin Forecast Center

The Colorado River Basin Forecast Center provides modeled soil moisture data (as opposed to single point observations) in map formats. Users can navigate to see either current conditions as compared to a percent normal value or may look at static, gridded maps of modeled soil moisture data from previous months (as in Figure 2).

NASA GRACE-FO Soil Moisture Maps

The NASA GRACE-FO website provides maps of gridded soil moisture conditions for the contiguous United States based on wetness percentile. Maps are updated weekly.

Evapotranspiration (ET)

Reference ET

Several weather-station networks in the basin states, mainly serving the agricultural sector, have instrumentation for all of the variables (temperature, solar radiation, humidity, winds) needed for real-time calculations of Reference ET. Typically, Reference ET is calculated hourly and daily, to the nearest 0.01 in. or 1 mm.


Colorado; 90 active stations in agricultural areas.


Arizona; 27 active stations in agricultural and urban areas.

UT AgWeather

Utah and adjacent areas in ID, WY, CO, NM; 130 active stations in agricultural and urban areas.

California Irrigation Management Information System (CIMIS)

California; 150 active stations in agricultural and urban areas.

Evaporative Demand Drought Index (EDDI)

EDDI is based on Reference ET (calculated from gridded NLDAS-2 meteorological data, using the same method as for the in-situ data above) and standardized relative to historical Reference ET for each gridpoint over the time window (2 weeks to 1 year) of interest. EDDI can offer early warning of agricultural and hydrologic drought by providing near-real-time information on the emergence or persistence of anomalous evaporative demand.


OpenET is an open-source platform and data viewing tool that brings together several satellite-based ET estimation methods to provide daily, monthly, and annual ET estimates at the field scale. The methods currently in the OpenET ensemble include ALEXI/DisAlexi, eeMETRIC, geeSEBAL, PT-JPL, SIMS, and SSEBop. Free registration required to view data.


Gaged streamflow - Real-time and Historical

USGS Water Watch interactive map

This interactive map shows over 530 active gages across the Colorado River Basin, and hundreds more in adjacent basins (Figure 2). Zoom in to see all gages, mouse-over a gage to see a yellow popup with its name and current streamflow statistics, and click on that gage's name within that popup to open the real-time data page for that gage. On the real-time data page, click "Change time span" to plot and retrieve historical gaged flow data.

USGS NWIS: Map View - Colorado River Basin

This interactive map is similar to the USGS Water Watch map but shows both the ~530 active gages (dark gray) and the ~380 inactive gages (light gray) across the basin for which daily streamflow over some period has been archived in the USGS National Water Information System. Click on a gage to get see the name; click "Access data" to go to the (old-USGS-style) data page for that gage.

Reclamation Boulder Canyon Operations Office (BCOO) - Data Explorer

Reclamation's BCOO provides near-real-time access to flow data from about 15 gages on the lower Colorado River, below Davis Dam, that are not part of the USGS network.

Colorado DWR Stations - Current and Historical

This interactive map shows over 360 active gages, and over 600 inactive ('historical') gages, within the 4 water divisions that comprise Colorado's portion of the Colorado River Basin. These gages include all those shown on the USGS map, along with others operated by DWR and local agencies. Zoom in to locate a gage of interest, mouse-over to see its name, and click to open a popup showing the length of the record. Click "View more details" to open the data page for that gage.

Unregulated inflow - Reclamation

24-Month Study Report - Archive (back to 2010)

Reclamation's 24-Month Study Reports, in addition to projecting system inflows and conditions ~24 months into the future, includes the observed (unregulated) inflows to each system reservoir for 12 months prior to the report date. These observed flows are shaded in gray and labeled "Historical".

Unregulated streamflow and inflow - NOAA CBRFC

CBRFC Streamflow Volumes

From the basin map shown, click the gage of interest so that the popup appears, then the link within the popup to open the webpage for that gage. For the current year and recent years, select the Water Year of interest at lower left (back to 2011); the forecast evolution plot will show that year's daily cumulative observed (unregulated) flows, in orange. For the full record (30-100 years), click Historical Volumes under "Data" in the lower right. A list of all historical April-July unregulated flows, in order of increasing flow, will be shown.

Adjusted streamflow - NRCS

NRCS Interactive Map - Observed Streamflow Volume

This link shows the NRCS Interactive Map customized to show the adjusted streamflow for the current water-year-to-date, as a % of the period-of-record average. Click on a gage of interest to bring up a popup, click on the popup to expand it, and then click on Data Reports and either Water Year Table or Water Year Chart for the current year's monthly flows. For historical flows at that gage, open the Water Year Table, click on the Create/Modify Report tab in the upper left. When the tab opens, click the first checkbox for 'stream volume, adjusted' then below that, change Time Period to "Period of Record", then click on the View Report tab at upper left.

Natural streamflow

Reclamation - Current Natural Flow Data

The Excel file linked on this page contains estimated monthly natural flows for the 20 locations in the Upper Basin, and 9 in the Lower Basin, that are the inflow points for the Colorado River Simulation System (CRSS). Most prominent among these is the Colorado River at Lees Ferry. These flow data are updated every year or so by Reclamation to extend the record forward, but they are always 1-2 years behind the most recently completed water year. Provisional data for the Lees Ferry gage only for the most recent water years are found on this page.



The TreeFlow resource provides access to data, metadata, and plots of nearly all existing tree-ring reconstructions of streamflow for the Colorado River Basin, as well as other river basins throughout the U.S. Currently there are 31 gages in the Upper Basin and 4 gages in the Lower Basin for which reconstructions are available.


The Paleoflow tool provides additional analysis and plotting options for the Colorado River Basin reconstructions that are available on TreeFlow, including dynamic time-series plots, analysis of extreme events, and comparisons of distributions (probability density functions) between two periods. Make sure Time Resolution = Annual to see the full list of reconstructions.

Seasonal streamflow forecasts


CBRFC has multiple ways to access and view their seasonal water supply forecasts and related data:

CBRFC Conditions Map - Water Supply Forecasts

The Conditions Map can display several different types of hydroclimate information, depending on the tab selected. The Water Supply Forecasts tab, when opened, defaults to the most probable (50% exceedance) values for the official 1st of month forecasts, but can also display the latest daily ESP forecasts ("Latest Model Guidance"). Clicking on the triangles (forecast points) brings up a thumbnail forecast evolution plot for that point; clicking within the plot opens a page specific to that forecast point, with an interactive forecast evolution plot and links to plots for previous years, calibration and validation data, and historical streamflow volumes for that point.

CBRFC Upper Colorado Situational Awareness

This page shows the most recent official forecasts for Lake Powell inflows (~all Upper Basin runoff) for April-July and the water year; maps of observed/modeled soil moisture, snowpack, and precipitation used to inform the forecasts; and graphs showing how the sub-basins' contributions and overall forecasted volume compares with average conditions.

CBRFC Water Supply Official Forecast List

This page features an interactive table with the official 1st of month forecasts for all forecast points. Like the forecast map, it links to the pages for each point.

CBRFC Water Supply Forecast Discussion

This document (PDF) discusses provides a general overview of the official (1st and 15th of month) CBRFC forecasts, describing the weather/watershed conditions that have led to the forecasts, as well as forecasts and outlooks for upcoming weather.

CBRFC Water Supply Webinars

From January through May, CRBFC presents one-hour webinars around the 7th of the month to explain the latest streamflow forecasts, the weather and snow conditions leading up to the forecasts, and the weather conditions forecasted for the next two weeks. Scroll down to "Presentations 20xx" for a link to the webinar archive for the current year; and then find the Water Supply Webinar" of interest. Both the slides and a recorded video with slides are available.


NRCS likewise has several ways to access and view their seasonal water supply forecasts and related data.

NRCS Interactive Map - Forecasted Streamflow Volumes

NRCS Interactive Map

The NRCS Interactive Map is a versatile tool to access and view all NRCS hydroclimate data, including the seasonal water supply forecasts. The link above has been specifically set up to show the most probable (50% exceedance) values for the current seasonal water supply forecasts, for individual points, but users can select other ways to visualize the forecast data, e.g., by basin, as percentiles, or for different forecast periods. Similar to the CBRFC Conditions Map, clicking on an individual forecast point will bring up a small window with the name of the point and forecasted streamflow volume; clicking on that window will bring up other options for viewing additional data for that point, including other statistics for the forecasted streamflow, and the observed streamflows for the water year.

NRCS Water Supply Forecast Chart

The Water Supply Forecast Chart shows the potential range for the forecasted streamflows (90%-70%-50%-30%-10% exceedances), similar to the shaded bands on the CBRFC forecast evolution plots. Note that the sub-basins within the CRB are shown by state; forecasts for Colorado R at Glen Canyon Dam (i.e., Lake Powell inflows) are accessed under Utah >Southwestern Utah.

NRCS State Basin Outlook Reports

The Basin Outlook Reports (also known as Water Supply Outlook Reports in some states) are issued monthly or semi-monthly from January through June by the state-level NRCS Snow Survey Offices, and supplement the NRCS seasonal water supply forecasts with narratives of statewide precipitation, snowpack, and water supply conditions, and additional graphics showing the water supply forecasts by sub-basin, alongside snowpack, precipitation, and reservoir conditions.

Colorado River Mid-Range Modeling System (CRMMS)

24-Month Study Reports

The output of the primary monthly run of CRMMS in 24-Month Study mode (using most probable inflows) is released around the 15th of each month. These results are formatted by Reclamation as a standardized set of data tables totaling 17 pages. The Upper Colorado and Lower Colorado regional offices package this set of data tables differently; Upper Colorado adds a 9-page narrative summary for the Upper Colorado reservoirs, while Lower Colorado adds a single cover page with very a brief summary. Note that both report "flavors" contain the results for both Upper Basin and Lower Basin reservoirs.

24-Month Study Reports - as distributed by Upper Colorado Region

24-Month Study Reports - as distributed by Lower Colorado Region

Supplemental 24-Month Study runs

As noted above, two supplemental runs of CRMMS in 24-Month Study mode are performed either 4 times per year, or monthly (as is true as of March 2022), depending on the projected reservoir conditions. These runs, based on minimum probable and maximum probable inflows, bracket most of the uncertainty in future conditions.

Probable Min/Probable Max runs

CRMMS Visualization Tool

This visualization tool shows the results of the latest month's runs of CRMMS in both 24-Month Study mode and Ensemble mode, for all 12 reservoirs represented in CRMMS. From the homepage, select the latest month, then the reservoir of interest, then "Dashboard" to see modeled monthly inflow, outflow, elevation, and storage, going out 24 months from the latest month.

Colorado River System 5-Year Probabilistic Projections

The CRMMS 5-year probabilistic projections of future conditions of the Colorado River system are typically updated by Reclamation in January, April, and August. The linked page shows the results of the most recent projections in tabular form, along with a description of the modeling approach and assumptions.

Colorado River Simulation System (CRSS)

Studies featuring long-term CRSS projections

Reclamation does not produce regular operational CRSS projections at long-term (>5-year) timescales. Instead, CRSS is run at longer timescales as needed for specific studies and policy analyses. Below are links to the studies (and report volumes therein) that drew on, and in some cases, presented CRSS results, in reverse chronological order:

  • International Boundary and Water Commission Minute 323 (2017)
  • International Boundary and Water Commission Minute 319 (2012)