NIDIS Upper Colorado River
Regional Drought Early Warning System
September 1, 2015


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.

 

Last Week Precipitation:

  • It was a wet week for the northeast portion of the UCRB with a broad brush of over half an inch of rainfall for western Colorado. Parts of Mesa, Garfield, and Pitkin Counties saw upwards of 2.00". 
  • The Upper Green River Basin, for the most part, received less than a quarter of an inch of rainfall. The northern side of the Uintah Range did a little better picking up between a quarter of an inch and an inch. 
  • The Duchesne Basin was fairly dry, but between 0.25 and 1.00" fell in the higher elevations around the basin. 
  • Southeast Utah received some spotty coverage between 0.50 and 1.00". Most of the area was between 0.10 and 0.50".
  • The headwaters of the Yampa and White Basins did well receiving 0.50-2.00" of rainfall. Farther west near the CO-UT border conditions were drier at 0.10-0.50".
  • The San Juans had some beneficial rains in La Plata and Archuletta Counties where over 0.50" of rain fell. Farther in northeast in Hinsdale and Mineral Counties it was far drier, and 0-0.25" fell across most of the region. 
  • The San Luis Valley was mostly between 0.10 and 0.25" for the week, but some spotty areas near the CO-NM border received over half an inch of rainfall. 
  • East of the divide it looks like most of the convection fired along the Palmer Divide as isolated areas received over half an inch of rainfall. Widespread coverage averaged in the 0.10-0.25" range fro the Denver metro area and east in Morgan, Washington, Lincoln, Adams, and Arapahoe Counties. Kit Carson and Cheyenne Counties received some of the heaviest and most widespread thunderstorm activity picking up over 0.50" across much of the region. 
  • The southeast corner of the state was generally dry receiving less than a tenth of an inch. 

August Precipitation:

  • With the exception of some strong thunderstorm activity along the eastern plains of Colorado, and some anomalously heavy rains in Duchesne and Carbon Counties in Utah, August was by and large a dry month for the UCRB and eastern Colorado. 
  • The Upper Green River Basin received some polarized precipitation totals in August. Uinta County did well picking up well over 125% of normal across much of the county. Sweetwater County was wetter than average in the western half and drier than average in the eastern half. 
  • August was also a polar month for northeast Utah precipitation-wise. The western Uintah Range in Daggett County, Uintah County, and Carbon County were all well above average for the month. In some places precipitation was over double average. The UT-CO border was dry from top to bottom with less than 75% of average precip. 
  • A couple isolated spots of western Colorado picked up above average precipitation for the month of August. Pitkin County and central Garfield County were over 125% of average. Northern Eagle County had a good month as well. Most of the western portion of the state was below 75% of average. The lowest areas with respect to average were northern and eastern Grand County, and Summit and Eagle Counties. In these areas less than 50% of normal precipitation fell. 
  • The San Luis Valley had a drier month than average at 50-90% of normal. 
  • East of the Divide, precipitation was mostly below normal, but there were some areas of above normal precipitation stemming from the Denver metro area and extending to the north and east. Morgan County, and eastern Weld and Adams Counties picked up over 200% of average August precipitation. Southern El Paso County, southern Bent County, and central Prowers County were well above average for the month also. The areas with the lowest precipitation totals with respect to normal were southern Yuma County and Huerfano County. 

Water Year 2015 Precipitation (Oct-Aug):

  • As a result of a very wet Spring, Colorado east of the divide is still above average across the board for the water year to date with a few small exceptions. Isolated areas of Custer and Huerfano Counties are showing below 100% of average. 
  • The UCRB is mostly close to, but a little below normal for the water year to date. 
  • Most of the Upper Green River Basin is between 50 and 90% of normal for the water year to date. Central Sweetwater County is in great shape at over 110% of normal. 
  • Northeastern Utah is mostly between 75 and 100% of normal for the water year to date. Farther to the west over higher terrain percentages are a little lower at between 50 and 75%. 
  • Southeastern Utah has balanced out to a fairly typical water year to date. The area is between 75 and 125% of normal. 
  • AHAPS indicates a very dry band in Conejos, Rio Grande, Mineral, and southwest Saguache Counties. Here precipitation is less than 50% of average for the water year to date. Radar does tend to struggle in this area, so it may be worth taking another look at when our precipitation figures update. Most of western Colorado is just slightly dry. The area is between 75 and 110% of normal for the water year to date. 
  • The Rio Grande Basin is now showing a mixed bag of above and below normal water year to date conditions. Southern Costilla County is doing very well at over 150% of normal for the water year to date. 

Additional Precipitation Links: (will take you to an outside website)
AHPS Precipitation
High Plains Regional Climate Center's ACIS Maps


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 short-term conditions while 6- and 9-month SPIs focus on long-term conditions. SPI data provided by High Plains Regional Climate Center.

Short Term (30-day):

  • SPIs for the UCRB are continuing a dry trend. with values between 0 and -2. SPIs around the Gunnison River are fairing better, with some areas around +1.
  • Slight improvements for the Upper Green River Basin with SPIs generally betwen 0 and -1, with values greater than 0 in the northern reaches of the Basin. 
  • Northcentral to northeast Utah are wetter than normal, between 0 and 2 SPI, while the point in far southest Utah in Uintah County is abnormally dry at -1.5 SPI.
  • Further southeast in Utah has a mix of SPI values between 1 (far southeast) and -1 (towards eastcentral Utah). 
  • The Yampa River Basin in northwest Colorado slightly dry at about 0 to -1 SPI. A point in Routt County has a value of +1 SPI. 
  • Western Colorado has a mix of values between -1.5 to +1 SPI. Further southwest sees wetter conditions, up to +1.5 at one point in Montezuma County.
  • The mountain ranges of the Rockies are in general very dry, with some points reaching as low as -2 SPI. Chaffee and Gunnison Counties are the expection, however, with SPIs greater than 0.
  • The Front Range has also been dry the last 30 days, with SPIs between -2.5 and 0.
  • Northeast Colorado remains generally dry. SPIs are between -1.5 and +1, while a point in Yuma County is nearly -3. 
  • The southeast portion of the state is still wet; around +1 SPI. 

Long Term (6-month):

  • Grand County remains the sole area that has below-normal SPIs for the UCRB (-1), while the rest of the basin is still wet. 
  • The Upper Green River is very wet at about +2 SPI. 
  • The entire eastern portion of Utah is wet in the long-term, with values around +1 (northeast) to +2/+2.5 (southeast). 
  • Western Colorado is showing SPIs mostly between 0 and +2.
  • SPIs along the front range remain very wet, up to +2 SPI. 
  • Far eastern Colorado continues the wet trend as well. Here values are mostly around +!, with some areas in Lincoln, Yuma, and Prowers Counties at nearly +2 SPI. 

Additional SPI Links: (will take you to an outside website)
WestWide Drought Tracker SPI Maps
HPRCC's SPI Maps



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.

Streamflow Statistics:

  • Streamflows in the UCRB appear to be leveling out to normal off-season levels over the last week and a half. 
  • 68% of the gages in the UCRB are reporting in the normal range for 7-day average streamflow. 9% of gages are reporting above to much above normal. There are no gages recording record high flows. 
  • 23% of the gages are recording below normal flows, with 6% of gages in the much below normal for 7-day average streamflow.
  • Streamflow on the Colorado River near the CO-UT state line is at the 55th percentile, 102% of average. 
  • The Green River at Green River, UT has come up slightly to the 31st percentile, 66% of average.
  • Streamflow at the San Juan near Bluff, UT is rallying yet again, and is at the 44th percentile, 66% of average. 

Additional Streamflow and River Links: (will take you to an outside website)
USGS Streamflow Drought
CBRFC Peak Flow Forecast Conditions Map


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).


The above image shows last month's and this month's current volumes of the major reservoirs in the UCRB, with percent of average and percent of capacity.
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.


VIC:

  • Soils are in the average to below average range in the Upper Green River Basin. Arid soils are expanding through the whole of Sweetwater County. The County is in the 2-30th percentile range, with a small sliver of 0-2nd percentile showing up. Far west Uinta and Lincoln Counties are above the 70th percentile. 
  • Much of central Uintah County is in the 2-30th percentile range with another sliver of 0-2nd percentile showing up, and western Duchesne County is between the 10th and 30th percentile, but the rest of the area is in the normal range. 
  • Southeast Utah is also showing soil moisture mostly in the normal range.  Southeast Emery County is showing a dry patch between the 5th and 30th percentile. The 70%+ region in Grand and San Juan Counties has nearly completely eroded with recent dryness. 
  • Western Colorado is almost entirely in the normal range. The far northwest corner of the state is between the 10th and 30th percentile. Isolated areas of Mesa, Pitkin, and Gunnison Counties are above the 70th percentile.
  • The San Luis Valley is mostly is showing soils mostly in the normal range, with a spot of 20th-30th percentile.
  • The Upper Arkansas River Basin, which has been moist since May, is back in the normal range for the most part. There are still some areas above the 70th percentile in Custer and Pueblo Counties. 
  • The Front Range is holding onto some wet soils primarily in Jefferson County. Most of the area is in the normal range. 
  • Soil have been in a drying trend for the northeastern portion of the state. Kit Carson, Yuma, and Washington Counties are seeing soils in the 10-30th percentile range. 
  • Soils in southeast Colorado are mostly in the normal range. Baca and Prowers Counties are showing some wet soils above the 70th percentile. 

VegDri:

  • The VegDri is showing mostly healthy conditions across the UCRB and eastern Colorado. There are a few pockets of pre-to moderate drought that have been in place for a couple weeks. 
  • The Upper Green River Basin shows mostly moist vegetative health conditions with some areas of pre to moderate drought along the northwest flank of the basin in Lincoln and Uinta Counties.
  • The Wasatch Mountains are showing pre to moderate drought. The Uintah Mountains are still holding on to a fair amount of pre-drought, especially in the northwestern portion of the range, but starting to show some wet conditions in the southern portion of the range. 
  • Conditions in the Duchesne River Basin are now showing mostly wet vegetative health. This degrades into pre-drought farther east into Uintah County. 
  • In southeast Utah vegetative health is mostly normal or slightly moist. 
  • Most of western Colorado is in the normal to slightly moist range. Pre-drought actually appears to be going away in Moffat and Rio Blanco Counties according to the VegDri. Southern Grand County and northern Eagle County are showing a fair amount of pre-to-moderate drought. 
  • The San Luis Valley is showing mostly moist vegetative health conditions.
  • The Upper Arkansas and Upper South Platte Basins are showing very moist vegetation conditions. This includes Chaffee, Park, Teller, Fremont, and Custer Counties. This area of very moist vegetation extends onto the Front Range and into El Paso, Elbert, Douglas, Jefferson, Adams, and Arapahoe Counties. This has been the case for a couple months now. 
  • Northeastern Colorado is holding on to moist conditions near the Front Range, but conditions closer to normal prevail farther east. There are spotty areas of pre-drought in Sedgewick, Phillips, Logan, Yuma, and Washington Counties. 
  • Southeast Colorado conditions are now mostly moist. Only very small and isolated traces of pre and moderate drought can be found in the area. 

Reservoirs (8/24):

  • Flaming Gorge is at 108% of its August average. 
  • Green Mtn is 110% of its August average and is 97% full.
  • Lake Granby is at 117% of its August average and 96% full. 
  • Blue Mesa is 117% of the August average, 96% full. 
  • Navajo is 103% of its August average. 
  • McPhee is now at 106% of its August average.
  • Lake Powell is now at 69% of the August average, 53% full.

Additional Surface Water Links: (will take you to an outside website)
NLDAS Drought Monitor
Bureau of Reclamation Upper Colorado River Basin Teacup Diagrams



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.

Reference Evapotranspiration:

  • Olathe: ET started the growing season at higher than average ET rates and since mid-May has been tracking below the lowest reference ET year of 1999.
  • Cortez: ET began a little above normal, but has been tracking below normal since early May.  ET was nearing the lowest year of 1995, but has tracked a little higher over the past week.
  • Center: Early season ET was higher than the track taken during the record year, but has slowed considerably with respect to the seasonal average, and is now tracking below average. 
  • Avondale: ET began just above average, but has slowed to below normal. It has been tracking at the normal rate over the past month and a half.
  • Idalia: ET started near average, then tracked with the low year of 2009 from mid-May to late July. It is still below average, but has taken a steep track over the past week.
  • Holyoke: ET started around normal and has dropped below normal since the second week of May. It has followed a fairly normal track for the past month or so with a notacable upward bend over the past week. 
  • Lucerne: ET has been tracking lower than the previous record low year in 2009 since the second week of May. It has gained some ground on the low year's track in the past three weeks. 


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.

Last Week Temperatures:

  • The UCRB was warmer than normal, with the largest departure in the far northwest portion of Colorado. 
  • Moving up into the Green River Basin in Wyoming, temperatures continue to be warmer than normal, at around +4 to 6 degrees.
  • Northeast Utah is between 4 to 6 degrees warmer than normal. Eastern and southeastern Utah was closer to normal for this week, with temperatures ranging from -2 to +2 degrees from normal.
  • The San Juan River area was 0 to 4 degrees warmer than normal throughout. The Rio Grande River Basin also saw this pattern, with a portion of Saguache County up near 6 degrees above normal. 
  • East of the divide, temperature departures began to fall off steadily from the front range to the high plains. North Weld and areas in Washington and Adams/Arapahoe Counties saw temperatures near 6 degrees warmer than normal. 
  • Southeast Colorado was the coolest, with Cheyenne, Kiowa, and Prowers Counties departing 0 to -2 degrees from normal. 

August Temperatures:

  • For August, the UCRB was about normal for temperatures, ranging from -2 to +2 degrees from normal. This is also true for the Upper Green River Basin in Wyoming. 
  • Throughout eastern Utah, temperatures were also roughly normal for August. Again, between -2 to +2 degrees.
  • Southwest Colorado was warmer than normal, generally around +2 degrees, with areas in La Plata and Ouray/Montrose Counties nearing +4 degrees. 
  • The Rockies were also warmer than normal. The southern portion near the Rio Grande River was the warmest at near +6 degrees warmer in Saguache County. 
  • The areas near the headwaters of the Arkansas River Basin were fairly warm at +4 degrees warmer than normal.
  • Much of the rest of the eastern portion of the state was 0 to +2 degrees warmer than normal. Exceptions are Sedgwick, Philips, and Logan Counties slightly cooler than normal, and Morgan County warmer at +2 to +4 degrees warmer. 


The top two images show Climate Prediction Center's Precipitation and Temperature outlooks for 8 - 14 days. The middle image shows the 3 months Precipitation outlook. The bottom left image shows the Hydrologic Prediction Center's Quantitative Precipitation Forecast accumulation for the five days between Tuesday 12Z and ending Sunday 12Z. The bottom right image shows the Climate Prediction Center's most recent release of the U.S. Seasonal Drought Outlook.

Short Term: (9/1)

  • Currently, high pressure sits just to the southeast of the UCRB and eastern Colorado. This afternoon and tomorrow this will keep conditions mostly stagnant with chances for afternoon showers over the western slopes of Colorado. The San Juans look the most likely to receive moisture. 
  • On Thursday and Friday an embedded upper level low pressure disturbance will traverse the northwestern portion of the basin. This will bring slightly cooler temperatures and increased chances for rainfall over western Colorado especially. Once again, the San Juans look to be the biggest benefactors, and are likely to receive over half an inch of moisture between now and the end of Thursday night. 
  • On Saturday and Sunday temperatures will cool by about ten degrees over eastern Colorado, possibly closer to fifteen degrees over the northeast quadrant of the state as the low pressure disturbance works its way to well northeast of the domain. Saturday and Sunday evenings offer the best chance of thunderstorms east of the divide over the next week, but accumulations are expected to be light, under 0.25" in most areas. 
  • By the beginning of next week eastern Colorado and the northeast part of the UCRB look to be giving way to a clearer, slightly cooler high pressure regime. The southwest portion of the state may benefit from additional moisture being wrapped in from the Pacific Ocean. 

Longer Term:

  • The 8-14 day precipitation outlook shows increased chances for above normal precipitation for eastern Colorado and for the eastern portion of the UCRB. These odds are highest in extreme southeast Colorado. The northwest portion of the UCRB is forecast equal chances of above and below normal precipitation.
  • The 8-14 day temperature outlook shows increased chances for above normal temperatures for southeast Colorado and increased chance for below normal temperatures for the northern portion of the Upper Colorado River Basin. The rest of the area is forecast equal chances of above and below normal temperatures. 
  • The Climate Prediction Center September through November precipitation outlook shows increased chances for above average precipitation across the entirety of the UCRB and Colorado east of the divide. These chances are maximized at low elevations in the southern portion of the basin. 
  • The seasonal drought outlook indicates that drought improvement and removal are likely for the western portion of the UCRB by the end of November. No drought development is likely over this time frame. 


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.

Summary for September 1st, 2015:  

It was a hot week for the Upper Colorado River Basin and Colorado east of the divide. Southeastern Colorado managed average to very slightly below average temperatures, but much of the domain was 2-4 degrees above average for the week. The Evaporative Demand Drought Index (EDDI) indicated a brutal week of evaporative stress for the central Rockies between August 19th and 26th. This was followed up by some really beneficial rainfall totals along the western slopes of 0.50-1.00" in most areas. Some of the biggest winners from this round of precipitation were the Uintah Mountain Range in Utah, and Mesa, Garfield, Pitkin, and northern Gunnison Counties in western Colorado. Streamflows in the UCRB did receive a slight bump as a result of this moisture, but are settling into post-runoff season levels. In spite of the recent moisture SPIs are still dry across most of western Colorado on the 30-day timescale. With the exception of Grand County these turn around at longer timescales (6 months). SPIs in the Duchesne River Basin are wet following the week's moisture, but soil moisture is still low in the region.

Northeast Colorado is showing some dry SPIs on the 30-day timescale. Yuma County is showing SPIs in the -1.5 to -2.5 range. Areas below the 30th percentile as shown by the VIC soil moisture model are expanding in the region as well. Even so, the area appears to be staying fairly healthy due to a cool, wet spring. Cumulative ET values are still well below average for the growing season to date and agricultural impacts reported have been minimal. 

Recommendations:

·         UCRB: It is recommended that southeast and central Grand County be downgraded to D0. This area received less reprieve that nearby areas with less than 0.25" of precipitation over the past week follow a very hot, dry period with high evaporative demand. For the time frame of August 19th-26th EDDI ranked the area above the 98th percentile for evaporative stress. This area is also showing pre-to-moderate vegetative health conditions as depicted by the VegDRI remote sensing product, and shows the only 6-month SPI in the area below 0. 

 

·         Eastern CO: Status quo

**Disclaimer: The above recommendations are recommendations only, based on data, impacts, and input from local experts. These recommendations are sent to the U.S. Drought Monitor author on Tuesdays. The USDM author has sole discretion on final changes made in the region and can accept, reject, or modify the above recommendations and may have additional modifications. Additionally, any recommendations discussed during the NIDIS webinars that are agreed upon by the local experts and USDM author are still subject to change. Changes are final and official as of Thursday morning, and can be viewed on the official U.S. Drought Monitor website.

Additional Drought Index Links: (will take you to an outside website)
Palmer Drought Severity Index for Climate Divisions Updated Weekly
WestWide Drought Tracker's PDSI Updated Monthly
Surface Water Supply Index

When available, maps and text are updated Tuesday afternoons.

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