9/6/2017 NIDIS Drought and Water Assessment NIDIS Intermountain West Drought Early Warning System September 5, 2017 Precipitation The images above use daily precipitation statistics from NWS COOP, CoCoRaHS, and CoAgMet stations. From top to bottom, and left to right: most recent 7-days of accumulated precipitation in inches; current month-to-date accumulated precipitation in inches; last month's precipitation as a percent of average; water-year-to-date precipitation as a percent of average. Standardized Precipitation Index http://climate.colostate.edu/~drought/current_assessment.php 1/12
Standardized Precipitation Index standardizes precipitation accumulations for a specified time period into percentile rankings. -1.0 to -1.5 is equivalent to a D1 to D2. -1.5 to -2.0 is equivalent to a D2 to D3. -2.0 and worse is equivalent to a D3 to D4. 30- and 60-day SPIs focus on shortterm conditions while 6- and 9-month SPIs focus on long-term conditions. SPI data provided by High Plains Regional Climate Center. Streamflow http://climate.colostate.edu/~drought/current_assessment.php 2/12
http://climate.colostate.edu/~drought/current_assessment.php 3/12
The top left image shows 7-day averaged streamflows as a percentile ranking across the UCRB. The top right image shows 7-day averaged discharge over time at three key sites around the UCRB: The Colorado River at the CO-UT state line; the Green River at Green River, UT; and the San Juan River near Bluff, UT. All streamflow data provided by United States Geological Survey. Surface Water The top left image shows VIC modeled soil moisture as a percentile ranking. The top right image shows satellite-derived vegetation from the VegDRI product (which updates on Mondays). http://climate.colostate.edu/~drought/current_assessment.php 4/12
9/6/2017 NIDIS Drought and Water Assessment The graphs shown below are plots of reservoir volumes over the past full year and current year to date (black). The dashed line at the top of each graphic indicates the reservoir's capacity, and the background color-coded shading provides context for the range of reservoir levels observed over the past 30 years. The data are obtained from the Bureau of Reclamation. Some of the reservoir percentiles don't line up at the new year due to differences in reservoir levels at the beginning of 1985 and the end of 2014. Dead storage has been subtracted. Note: Lake Granby data are obtained from the Colorado Division of Water Resources, and only goes back to the year 2000. Evaporative Demand The above images are of reference evapotranspiration (ET) from CoAgMET sites across Colorado. Reference ET assumes the amount of water that will evaporate from a well-irrigated crop. Higher ET rates occur during hot, dry, and windy conditions. Lower ET rates are more desirable for crops. See a map of locations for the above ET sites. http://climate.colostate.edu/~drought/current_assessment.php 5/12
The above images are available courtesy of NOAA s Evaporative Demand Drought Index (EDDI). Drought classification listed is a function of the depth of reference evapotranspiration accumulated over a given period of record with respect to a climatology of 1981-2010. The drought categories displayed are in line with the US Drought Monitor's Percentile Ranking Scheme. Data used to generate these maps come from the North American Land Data Assimilation System Phase-2 (NLDAS-2) project, which assimilates observations of temperature, wind speed, radiation, and vapor pressure deficit. The date indicates the last day of the period of record, and the week number indicates the window size for the period of record. Temperature http://climate.colostate.edu/~drought/current_assessment.php 6/12
All images show temperature departures from average over different time periods (last 7 days on top left; month-to-date on top right; last full month on bottom). Temperature departure maps provided by HPRCC ACIS. Outlook http://climate.colostate.edu/~drought/current_assessment.php 7/12
The top two images show Climate Prediction Center's Precipitation and Temperature outlooks for 8-14 days. The middle image shows the Weather Prediction Center's Quantitative Precipitation Forecast accumulation for seven days. The bottom left image shows the 3-month precipitation outlook from Climate Prediction Center, and the bottom right image shows the Climate Prediction Center's most recent release of the U.S. Seasonal Drought Outlook. http://climate.colostate.edu/~drought/current_assessment.php 8/12
> Summary and Recommendations http://climate.colostate.edu/~drought/current_assessment.php 9/12
Above is the most recent release of the U.S. Drought Monitor map for the UCRB region. Below shows the proposed changes for this week, with supporting text. http://climate.colostate.edu/~drought/current_assessment.php 10/12
Summary: September 5, 2017 A warm, dry, high pressure airmass has had a stranglehold on the western United States for weeks now and in some areas longer. This system has remained far enough north and west that areas of southern and eastern Colorado have had access to some monsoonal moisture. South-central Colorado managed to squeeze out some rain mid-week last week, and a larger chunk of eastern Colorado saw thunderstorm activity last Thursday evening. Warm and dry air took over from Friday through Sunday including record heat for weather stations all over Colorado and the Upper Colorado River Basin. A cool front moved through late this weekend, but it was dry and brought smoke from the northwest rather than rain. Despite above average winter precip, eastern Utah and the west slopes of Colorado are now experiencing precipitation deficits for timescales going back to the start of last water year. The Colorado, Yampa, and White River Valleys are showing 70-90% of normal precipitation over this time frame. Spotty areas of eastern Utah and western Colorado are below 70% for the water year to date. This time of year we expect streams and rivers to return closer to base flow levels, for the atmosphere to begin to dry out, and for soil moisture surpluses from thunderstorms to be short- http://climate.colostate.edu/~drought/current_assessment.php 11/12
lived. Flows in the headwaters of the Colorado River, along the San Juan River, and on the Rio Blanco River are below or much below normal even for this time of year. Soil sensor readings in eastern Utah show wilted soils across the board down to 8" depth and values in the normal range at 20" and 40". This is not an unusual signal for September, especially following short-term dryness. Agricultural impacts from recent dryness are likely for the rare dry land operation on the west slope. Luckily, most growing operations do use irrigation, and 2017 gave above average water supply from snowpack. Scattered showers may continue for the next two days in the Four Corners Region. Moisture should return and expand across the west slope by Thursday, but rainfall totals will still mostly be less than a quarter of an inch. Temperatures are likely to remain hotter than normal next week with an increase in chances for above average precipitation for the UCRB, especially southern Utah. Recommendations UCRB: It is recommended that D1 be added to southeast Uintah County in Utah and to western Rio Blanco and Garfield Counties in Colorado. This recommendation would include northeast Mesa County. 6-month precipitation anomalies in the white river are below -1 sigma. The White River is showing much below average 28-day average streamflows for this time of year. It is recommended that D1 be added to northeast San Juan County and southeast Grand County in Utah as well as northwest Montrose County and southwest Mesa County in Colorado. These areas are showing both short and long term precipitation deficits that are now reflected by browning vegetation and lower than average streamflows. It is recommended that D0 be widely expanded in eastern Utah and western Colorado as well as south-central Wyoming. This recommendation includes central Wayne County, east-central Garfield County, and west-central San Juan County in Utah. It includes northern San Miguel County, eastern Montrose County, eastern Delta County, north and central Gunnison County, Chaffee County, Pitkin County, eastern Garfield County, Eagle County, Summit County, Grand County, Routt County, and the D-nada remnants of Moffat and Jackson County in Colorado. It includes south-central Carbon County in Wyoming. These areas are showing water year to date precipitation deficits of growing concern in part thanks to recent dryness. Eastern Colorado: Status quo. http://climate.colostate.edu/~drought/current_assessment.php 12/12