Colorado Water Supply Outlook Report February 1, 2018 NRCS snow surveyors near the Rio Blanco snow course in the Flat Tops east of Meeker. This survey revealed 5.1” of snow water equivalent which is 59 percent of the 1981-2010 median value. As of February 1st snowpack throughout the combined Yampa and White River basins was 70 percent of normal. Photo By: Tiffany Jehorek Date: January 31st, 2018 REMINDER: We are soliciting field work photos from the field again this year. Each month we will pick one to grace the cover of this report! Please include information on where, when and of who/what the photo was taken. Contents Colorado Statewide Water Supply Conditions........................................................................................................................ 3 Summary ............................................................................................................................................................................. 3 Snowpack ............................................................................................................................................................................ 4 Precipitation ........................................................................................................................................................................ 5 Reservoir Storage ................................................................................................................................................................ 6 Streamflow .......................................................................................................................................................................... 7 GUNNISON RIVER BASIN ......................................................................................................................................................... 8 UPPER COLORADO RIVER BASIN ............................................................................................................................................. 2 SOUTH PLATTE RIVER BASIN ................................................................................................................................................... 2 YAMPA, WHITE, NORTH PLATTE, AND LARAMIE RIVER BASINS ............................................................................................. 2 ARKANSAS RIVER BASIN .......................................................................................................................................................... 2 UPPER RIO GRANDE RIVER BASIN ........................................................................................................................................... 2 SAN MIGUEL, DOLORES, ANIMAS, AND SAN JUAN RIVER BASINS .......................................................................................... 2 How to Read Snowpack Graphs .............................................................................................................................................. 2 How Forecasts Are Made ........................................................................................................................................................ 1 Interpreting the Forecast Graphics ......................................................................................................................................... 1 The U.S. Department of Agriculture (USDA) prohibits discrimination against its customers. 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Colorado Statewide Water Supply Conditions Summary Colorado Statewide Time Series Snowpack Summary Based on Provisional SNOTEL data as of Feb 01, 2018 20 18 Snow Water Equivalent (inches) 16 Current as Pct of Normal: 59% Current as Pct of Avg: 57% Current as Pct of Last Year: 39% Current as Pct of Peak: 36% Normal as Pct of Peak: 61% Pct of Normal Needed to Reach Peak: 164% Normal Peak Date: Apr 07 14 12 10 8 6 4 2 0 Oct 01 Nov 01 Dec 01 Median Jan 01 Feb 01 Mar 01 WY2015 WY2016 Apr 01 May 01 WY2017 Jun 01 Jul 01 Average Aug 01 Sep 01 WY2018 The general patterns of snowpack, precipitation, reservoir storage, and streamflow forecasts observed in the first three months of water year 2018 largely continued through the month of January. Southern Colorado has remained abnormally dry and continues to hold well below normal snowpack, which is also reflected in low streamflow forecasts. Snowpack is 31 percent of normal in the Upper Rio Grande basin and only 34 percent in the combined San Miguel, Dolores, Animas, and San Juan basins to the west. Conversely, snowpack in the North and South Platte basins is 82 and 80 percent of normal, respectively, and they hold several forecasts for near average streamflows, but currently no rivers in Colorado are forecasted to have above average summer flows. While snowpack still lags well below normal in southern Colorado, January did bring the most precipitation of any month of the water year to date, which did help in some capacity. Statewide, mountain precipitation in January was 70 percent of average with the South Platte receiving the most, at 85 percent, and the Upper Rio Grande the least at 50 percent of average. This leaves statewide water year-to-date precipitation at 62 percent of normal and snowpack at 59 percent, a slight increase over a month ago. Despite below normal snowpack and streamflow forecasts across the state, the good news is that every major basin in Colorado is still maintaining above average reservoir storage volumes, which may become critical this summer. Statewide reservoir storage remained unchanged from a month ago and resides at 115 percent of average. Snowpack The storm track failed to deliver the moisture laden storms that Colorado was hoping for last month. The mountains across the state continue to hold a below normal snowpack, making the possibility of achieving a normal snowpack peak a dwindling prospect. There continues to be a strong gradient in snowpack conditions deteriorating north to south across the state, with the North and South Platte River basins having the most favorable conditions at 82 and 80 percent of median, respectively. However, these two basins both experienced a drop compared to normal conditions since last month after monthly snowpack accumulations in January were below normal, except at a handful of SNOTEL sites. Colorado’s remaining major river basins all experienced a slight boost to percent of normal snowpack, however these improvements are little consolation given the grim snowpack present in the southern river basins. The combined San Miguel, Dolores, Animas, and San Juan River basins are currently at 34 percent of median and the Upper Rio Grande is at 31 percent. In these two basins, more than half of the snow measurement sites (snow courses and SNOTEL) are at or near record low levels. The mountains are already about two-thirds of the way through a typical snowpack accumulation season, so impressive snowfall that is considerably above average is needed to overcome the snow drought that dominated these basins for the first half of the water year. Snowpack amounts in the Gunnison and Arkansas River basins are only slightly better, at 48 and 55 percent of median respectively. The Upper Colorado and combined Yampa and White River basins are in the middle of the range of the current snowpack values across the state, and are at 73 and 70 percent of median respectively. Statewide, snowpack is at a dismal 59 percent of median. A major shift in precipitation patterns is badly needed to bring the state’s snowpack anywhere close to normal levels. Precipitation January precipitation amounts were an improvement over the previous monthly accumulations in many of Colorado’s major river basins, however precipitation for the month was below normal across the entire state. Additionally, water year-to-date precipitation is no longer above normal for any basin. The northern basins received precipitation accumulations in January that were nearest to normal amounts and these basins have the highest water year precipitation with respect to normal. The South Platte, combined Yampa, White, and North Platte, and Colorado River basins all received between 80 and 85 percent of average monthly precipitation. The January accumulations resulted in a minimal change to the water year-to-date precipitation for the Colorado and combined Yampa, White, and North Platte River basins, which are at 76 and 77 percent of average respectively. Water year-to-date precipitation fell slightly in the South Platte, but the basin remains near normal at 98 percent of average for the water year. The Gunnison received precipitation that was 73 percent of average for January, which while still below average, boosted the water year precipitation in the basin from 36 percent to 46 percent of average. The Arkansas and combined San Miguel, Dolores, Animas, and San Juan River basins were at 58 and 55 percent of average for the month, while the Upper Rio Grande River basin experienced the driest conditions in the state and received only 50 percent of average January precipitation. The combined San Miguel, Dolores, Animas, and San Juan River basins continue to have the lowest water-year-to date precipitation in the state. Average SNOTEL precipitation for these basins is only 4 inches for the water year, which is 29 percent of average. Statewide, January precipitation was 70 percent of average, while the water year precipitation rose slightly to 62 percent of average. Reservoir Storage Colorado Reservoir Storage Oct-17 Apr-18 Nov-17 May-18 Dec-17 Jun-18 Jan-18 Jul-18 Feb-18 Aug-18 Mar-18 Sep-18 180% Percent of Average Useable Storage 160% 140% 120% 100% 80% 60% 40% 20% 0% Gunnison Colorado South Platte Yampa, White & North Platte Arkansas Upper Rio Grande San Miguel, Dolores, Animas & San Juan Statewide Reservoir levels have fluctuated minimally throughout water year 2018 so far, relative to normal amounts. Statewide reservoir storage was 115 percent of average as of February 1st, the same value as of a month ago. Storage across the major basins has shown change but generally nothing too substantial and all basins remain at above average levels. The most significant declines over the last four months have been in the Arkansas basin, but these reservoirs still have the highest storage in the state, at 140 percent of average. On the low end, the Gunnison and combined San Miguel, Dolores, Animas, and San Juan basins are holding 104 and 105 percent of average storage, respectively. Storage is 109 percent of normal in the South Platte River basin and 116 percent in the Upper Colorado. The Upper Rio Grande River basin continues to hold well above average reservoir storage, at 123 percent, the same as last month. Given the very low snowpack levels in the Rio Grande this is an especially important year to have good reservoir storage, as it has been below average since 2002. The combined Yampa, White, and North Platte River basins lie slightly lower than the Rio Grande relative to normal, holding 120 percent of their average storage values. Given the current low snowpack and streamflow forecasts across the state, particularly in southern Colorado, these above average reservoir volumes may become a critical resource this summer. Streamflow February 1st streamflow forecasts vary widely across the state, largely following the trend of a well below average snowpack in southern Colorado and closer to normal values in the northern Front Range. While there are many streams in the Colorado River headwaters and the northern portion of the South Platte basin forecast to have near average streamflows this summer, there are currently no points in the state forecasted to have above average streamflow at the 50% chance of exceedance level. On the high end, several streams in the South Platte and Colorado River basins are forecast to have 91 percent of average April-July flows, but other forecasts across these basins also range to as low as 59 percent of normal. Across the combined Yampa and White River basins, forecasts range from a low of 48 percent on Elkhead Creek to a high of 70 percent on the Elk River near Milner. Forecasted streamflow volumes generally continue to get lower and lower moving towards the southwest corner of the state. The average of streamflow forecasts across the Gunnison basin is for 55 percent of normal volumes. Forecasts for the rivers and streams of the Rio Grande basin have not changed dramatically from a month ago and currently average out to around 50 percent of normal, but with many substantially lower. The combined San Miguel, Dolores, Animas, and San Juan basins of far southwest Colorado currently have the most consistently low streamflow forecasts in the state. The Dolores, Animas, and San Juan rivers are all forecast to have 43-45 percent of normal flows and the total range of forecasts in these combined basins is 33-56 percent. Forecasts in the Arkansas basin vary the most of any in the state, from a high of 80 percent of average for the Arkansas River at Salida to a low of 20 percent for Grape Creek at Westcliffe. GUNNISON RIVER BASIN February 1, 2018 Snowpack in the Gunnison River basin is below normal at 48% of the median. Precipitation for January was 73% of average which brings water year-to-date precipitation up to 46% of average. Reservoir storage at the end of January was 104% of average compared to 108% last year. Current streamflow forecasts range from 72% of average for the Slate River near Crested Butte to 27% for Surface Creek at Cedaredge. Gunnison River Basin Mountain Snowpack Snow Water Equivalent (Inches) 30 25 20 15 10 5 Historic Snowpack Range Median Snowpack *SWE values calculated using daily SNOTEL data only Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov Oct 0 50% Exceedance Mountain Precipitation 80 70 Percent of Average 60 50 40 30 20 10 0 Oct Nov Dec Monthly Jan Feb Mar Year-to-date Apr May Watershed Snowpack Analysis February 1st, 2018 Sub-Basin Upper Gunnison Surface Creek Uncompahgre Basin-Wide Total # of Sites Last Year % % Median Median 17 49 172 3 29 153 4 46 164 21 48 171 *SWE values calculated using first of month SNOTEL data and snow course measurements Reservoir Storage Percent Average 120% Percent Capacity 100% 80% 60% 40% 20% 0% 1 Reservoir Storage End of January 2018 Reservoir BLUE MESA RESERVOIR CRAWFORD RESERVOIR CRYSTAL RESERVOIR FRUITGROWERS RESERVOIR FRUITLAND RESERVOIR MORROW POINT RESERVOIR PAONIA RESERVOIR RIDGEWAY RESERVOIR SILVERJACK RESERVOIR TAYLOR PARK RESERVOIR VOUGA RESERVOIR BASINWIDE Number of Reservoirs Current Last Year Average Capacity (KAF) (KAF) (KAF) (KAF) 554.5 586.6 514.6 830 5.0 6.0 7.7 14 7.8 8.5 7.6 18 2.2 2.8 3.4 4 1.1 0.7 1.3 9 109.3 112.0 111.4 121 2.7 1.5 3.5 15 60.9 63.7 69.2 83 2.3 2.2 5.3 13 74.2 69.5 66.9 106 0.7 0.9 0.7 0.92 820.7 854.4 791.6 1213.4 11 11 11 11 GUNNISON RIVER BASIN Water Supply Forecasts February 1, 2018 Forecast Exceedance Probabilities and Volumes Forecast Forecast Drier Future Conditions Wetter POW Period Box labels on chart are volumes of water in thousand acre-feet. Tayloerl Taylor Apr-Jul 43 58 83 105 Park Reservoir SlateRnr Apr-Jul 42 52 - 68 81 Crested Butte EastRatAlmont Apr-Jul 70 96 I 139 175 GunnisonR Apr-Jul 122 179 I 275 355 Near Gunnison TomichiCkat Apr-Jul 6.7 13 ?r 24 35 Sargents Cochetopa Apr-Jul 4 11 18 Rock Ck nr Parlin TomichiCkat Apr-Jul 59 19 50 82 Gunnison LakeFkat Apr-Jul 44 62 I 90 114 Gateview GunnisonRat Apr-Jul 200 300 470 620 Blue Mesa Dam Muddka bl Apr-Jul 8.3 2O 44 68 Paonia Reservoir Mar-Jun 11 23 46 68 NF GunnisonR Apr-Jul 65 100 - 159 210 nr Somerset Surface Ck at Apr-Jul 2.2 3.5 - 5.8 7.8 Cedaredge UncompahgreR Apr-Jul 31 45 - 68 88 blRidgway Reservoir UncompahgreR Apr-Jul 26 47 86 121 at Colona Gunnisoanr Apr-Jul 275 465 - 795 1100 Grand Junction 100 110 120 130 Percent of Average (30 Yr Period) 10% Exceedance Forecast (KAF) 5% Exceedance 30% Exceedance Forecast (KAF) There is a 30% chance that flows will exceed this voiume. 50% Exceedance Forecast (KAF) There is a 50% chance that flows will exceed this volume. 70% Exceedance Forecast (KAF) There is a 70% chance that flows will exceed this voiume. 90% Exceedance Forecast 95% Exceedance UPPER COLORADO RIVER BASIN February 1, 2018 Snowpack in the Colorado River basin is below normal at 73% of the median. Precipitation for January was 83% of average which brings water year-to-date precipitation to 76% of average. Reservoir storage at the end of January was 116% of average compared to 108% last year. Current streamflow forecasts range from 91% of average for the inflow to Lake Granby to 59% for the Roaring Fork at Glenwood Springs. Colorado River Basin Mountain Snowpack Snow Water Equivalent (Inches) 25 20 15 10 5 Historic Snowpack Range Median Snowpack Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov Oct 0 50% Exceedance *SWE values calculated using daily SNOTEL data only Mountain Precipitation 120 Percent of Average 100 80 60 40 20 0 Oct Nov Dec Monthly Jan Feb Mar Year-to-date April May Watershed Snowpack Analysis February 1st, 2018 Sub-Basin Blue River Upper Colorado Muddy Creek Eagle River Plateau Creek Roaring Fork Williams Fork Willow Creek Basin-Wide Total Last Year % # of Sites % Median Median 8 91 157 36 79 151 5 89 151 5 59 130 6 39 145 9 67 171 5 72 137 5 85 187 48 73 154 *SWE values calculated using first of month SNOTEL data and snow course measurements Reservoir Storage Percent Average 160% Percent Capacity 140% 120% 100% 80% 60% 40% 20% 0% DILLON RESERVOIR LAKE GRANBY GREEN HOMESTAKE RUEDI VEGA WILLIAMS WILLOW WOLFORD SHADOW BASINWIDE MOUNTAIN RESERVOIR RESERVOIR RESERVOIR FORK CREEK MOUNTAIN MOUNTAIN 1 RESERVOIR RESERVOIR RESERVOIR RESERVOIR RESERVOIR Reservoir Storage End of January 2018 Current Last Year Average Capacity (KAF) (KAF) (KAF) (KAF) DILLON RESERVOIR 235.1 219.0 218.4 249 LAKE GRANBY 417.2 350.0 302.9 466 GREEN MOUNTAIN RESERVOIR 63.7 60.4 77.1 147 HOMESTAKE RESERVOIR 41.0 42.1 31.7 43 RUEDI RESERVOIR 69.4 67.8 72.4 102 VEGA RESERVOIR 10.1 11.0 12.4 33 WILLIAMS FORK RESERVOIR 66.0 74.4 63.8 97 WILLOW CREEK RESERVOIR 6.3 6.7 6.9 9 WOLFORD MOUNTAIN RESERVOIR 54.6 50.8 43.6 66 SHADOW MOUNTAIN RESERVOIR 17.4 17.4 17.3 18 BASINWIDE 980.9 899.5 846.5 1229.8 Number of Reservoirs 10 10 10 10 Reservoir Forecast Point UPPER COLORADO RIVER BASIN Water Supply Forecasts February 1, 2018 Forecast Exceedance Probabilities and Volumes Forecast Drier Future Conditions Penod Box labels on chart are volumes of water in thousand acre-feet. Wetter Colorado bl Lake Granby Willow Ck bl Willow Ck Reservoir Williams Fk bl Williams Fk Reservoir Muddy Creek bl Wolford Reservoir Blue bl Dillon Reservoir Blue bl Green Mountain Reservoir Eagle bl Gypsum Colorado nr Dotsero Frying Pan at Ruedi Roaring Fk at Glenwood Springs Colorado nr Cameo 138 175 230 24 34 51 Apr-Jul Apr-Jul Apr-Jul 52 275 65? Apr-Jul Apr-Jul Apr-Jul 152 200 1380 375 Apr-Jul Apr-Jul 1730 63 83 115 Apr-Jul 141 255 345 - 485 610 Apr-Jul 2380 1030 1370 1920 Apr-Jul 100 110 120 Percent of Average (30 Yr Period) I 130 140 150 I 10% Exceedance Forecast (KAF) El 5% Exceedance 70% Exceedance Forecast (KAF) There is a 70% chance that ?ows will exceed this volume. 50% Exceedance Forecast There is a 50% chance that ?ows will exceed this volume. 30% Exceedance Forecast (KAF) There is a 30% chance that flows will exceed this volume. 90% Exceedance Forecast (KAF) El 95% Exceedance SOUTH PLATTE RIVER BASIN February 1, 2018 Snowpack in the South Platte River basin is below normal at 80% of the median. Precipitation for January was 85% of average which brings water year-to-date precipitation to 98%. Reservoir storage at the end of January was 109% of average compared to 104% last year. Streamflow forecasts range from 91% of average for Boulder Creek near Orodell to 62% for the inflow to Antero Reservoir. South Platte River Basin Mountain Snowpack Snow Water Equivalent (Inches) 30 25 20 15 10 5 Historic Snowpack Range Median Snowpack *SWE values calculated using daily SNOTEL data only Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov Oct 0 50% Exceedance Mountain Precipitation 140 Percent of Average 120 100 80 60 40 20 0 Oct Nov Dec Monthly Jan Feb Mar Year-to-date Apr May Watershed Snowpack Analysis February 1st, 2018 Sub-Basin Big Thompson Boulder Creek Cache La Poudre Clear Creek Saint Vrain Upper South Platte Basin-Wide Total Last Year % # of Sites % Median Median 7 78 160 6 79 170 10 90 156 4 87 145 2 60 245 16 71 139 45 80 156 *SWE values calculated using first of month SNOTEL data and snow course measurements Reservoir Storage Percent Average 250% Percent Capacity 200% 150% 100% 50% 0% 1 Current Last 2018 Year Reservoir Storage End of January Reservoir ANTERO RESERVOIR BARR LAKE BLACK HOLLOW RESERVOIR BOYD LAKE CACHE LA POUDRE CARTER LAKE CHAMBERS LAKE CHEESMAN LAKE COBB LAKE ELEVENMILE CANYON RESERVOIR EMPIRE RESERVOIR FOSSIL CREEK RESERVOIR GROSS RESERVOIR HALLIGAN RESERVOIR HORSECREEK RESERVOIR HORSETOOTH RESERVOIR JACKSON LAKE RESERVOIR JULESBURG RESERVOIR LAKE LOVELAND RESERVOIR LONE TREE RESERVOIR MARIANO RESERVOIR MARSHALL RESERVOIR MARSTON RESERVOIR MILTON RESERVOIR POINT OF ROCKS RESERVOIR PREWITT RESERVOIR RIVERSIDE RESERVOIR SPINNEY MOUNTAIN RESERVOIR STANDLEY RESERVOIR TERRY RESERVOIR UNION RESERVOIR WINDSOR RESERVOIR BASINWIDE Number of Reservoirs (KAF) 20.3 26.8 3.4 34.6 8.9 55.4 5.8 71.0 19.1 99.8 25.8 9.3 28.3 6.4 11.8 85.8 24.2 16.5 5.8 6.8 4.0 7.1 6.4 19.3 59.2 18.9 41.8 35.8 42.0 6.0 12.0 8.8 827.0 32 (KAF) 14.5 24.0 3.3 27.6 6.8 71.5 2.6 68.5 17.0 99.4 23.7 9.3 12.1 6.4 7.5 114.5 24.0 12.7 3.9 5.2 1.0 5.9 5.1 19.4 50.9 20.1 45.1 27.6 32.1 4.8 9.3 11.2 787.0 32 Average (KAF) 15.3 24.0 2.8 27.8 6.4 78.3 3.1 63.7 11.7 95.9 22.6 6.9 14.3 4.5 10.4 94.7 23.1 16.9 6.8 6.4 3.0 5.6 5.9 15.8 51.1 15.7 37.3 29.0 35.7 5.0 10.0 8.3 758.0 32 Capacity (KAF) 20 30 7 48 10 109 9 79 22 98 37 11 30 6 15 150 26 21 10 9 5 10 13 24 71 28 56 49 42 8 13 15 1079.5 32 There is not enough information to produce a valid forecast, forecasts will be produced starting in April. YAMPA, WHITE, NORTH PLATTE, AND LARAMIE RIVER BASINS February 1, 2018 Snowpack in the Yampa, White & North Platte basins is below normal at 75% of the median. Precipitation for January was 80% of average and water year-to-date precipitation is 77% of average. Reservoir storage at the end of January was 120% of average compared to 121% last year. Streamflow forecasts range from 98% of average for the Laramie River at Woods Landing to 48% for Elkhead Creek above Long Gulch. Yampa, White & North Platte River Basins Mountain Snowpack Snow Water Equivalent (Inches) 40 35 30 25 20 15 10 5 Historic Snowpack Range Median Snowpack *SWE values calculated using daily SNOTEL data only Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov Oct 0 50% Exceedance Mountain Precipitation 100 90 Percent of Average 80 70 60 50 40 30 20 10 0 Oct Nov Dec Monthly Jan Feb Mar Year-to-date April May Watershed Snowpack Analysis February 1st, 2018 Sub-Basin Laramie North Platte Total Laramie & North Platte Elk Yampa White Total Yampa & White Little Snake Basin-Wide Total Last Year % # of Sites % Median Median 4 95 149 12 79 137 16 82 139 2 68 135 11 73 128 4 66 134 14 70 128 9 72 132 35 75 135 *SWE values calculated using first of month SNOTEL data and snow course measurements Reservoir Storage 140% Percent Average Percent Capacity 120% 100% 80% 60% 40% 20% 0% STAGECOACH RESERVOIR NR OAK CREEK YAMCOLO RESERVOIR Reservoir Storage End of January 2018 Current Last Year Average Capacity Reservoir (KAF) (KAF) (KAF) (KAF) STAGECOACH RESERVOIR NR OAK CREEK33.4 34.5 28.2 37 YAMCOLO RESERVOIR 7.6 6.7 5.8 9 BASINWIDE 41.0 41.2 34.0 45.2 Number of Reservoirs 2 2 2 2 BASINWIDE 1 YAMPA-WHITE-NORTH PLATTE RIVER BASINS Water Supply Forecasts February 1, 2018 Forecast Exceedance Probabilities and Volumes Forecast Forecast Drier Future Conditions Wetter POW Period Box labels on chart are volumes of water in thousand acre-feet. North PlatteRnr Apr-Jul 55 132 235 315 Northgate Apr-Sep 63 147 260 345 LaramieRand Apr-Jul 54 89 137 172 Pioneer nr Woods Apr-Sep 62 99 151 188 YampaRab Apr-Jul - 2 7 19 28 Stagecoach Reservoir YampaRat Apr-Jul 89 121 - 189 240 Steamboat Apr-Jul 150 182 - 270 335 Elkhead Ckab Apr-Jul 15 22 I 48 66 Long Gulch YampaRnr Apr-Jul 300 - 425 - 635 815 Maybell LittleSnakeRnr Apr-Jul 63 - 86 131 169 Slater Little SnakeRnr Apr-Jul 115 155-? 240 330 Dixon Little SnakeRnr Apr-Jul 97 157 260 355 Lily WhiteRnr Apr-Jul 87 122 - 179 225 Meeker 100 120 140 160 Percent of Average (30 Yr Period) 10% Exceedance 30% Exceedance 50% Exceedance 70% Exceedance 90% Exceedance Forecast (KAF) Forecast (KAF) Forecast (KAF) Forecast (KAF) Forecast (KAF) El 0 There is a 30% chance that There is a 50% chance that There is a 70% chance that El 0 5 Exceedance ?ows will exceed this volume. ?ows will exceed this volume. ?ows will exceed this volume. 95? Exceedance ARKANSAS RIVER BASIN February 1, 2018 Snowpack in the Arkansas River basin is below normal at 55% of the median. Precipitation for January was 58% of average which brings water year-to-date precipitation to 56% of average. Reservoir storage at the end of January was 138% of average compared to 99% last year. Current streamflow forecasts range from 80% of average for the Arkansas River at Salida to 20% of average for Grape Creek near Westcliffe. Arkansas River Basin Mountain Snowpack Snow Water Equivalent (Inches) 25 20 15 10 5 Historic Snowpack Range Median Snowpack *SWE values calculated using daily SNOTEL data only Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov Oct 0 50% Exceedance Mountain Precipitation 70 Percent of Average 60 50 40 30 20 10 0 Oct Nov Dec Monthly Jan Feb Mar Year-to-date April May Watershed Snowpack Analysis February 1st, 2018 Sub-Basin Upper Arkansas Cucharas & Huerfano Purgatoire Basin-Wide Total Last Year % # of Sites % Median Median 9 75 169 5 20 142 2 24 221 16 55 164 *SWE values calculated using first of month SNOTEL data and snow course measurements Reservoir Storage Percent Average 250% Percent Capacity 200% 150% 100% 50% 0% 1 Reservoir Storage End of January 2018 Reservoir ADOBE CREEK RESERVOIR CLEAR CREEK RESERVOIR CUCHARAS RESERVOIR GREAT PLAINS RESERVOIR HOLBROOK LAKE HORSE CREEK RESERVOIR JOHN MARTIN RESERVOIR LAKE HENRY MEREDITH RESERVOIR PUEBLO RESERVOIR TRINIDAD LAKE TURQUOISE LAKE TWIN LAKES RESERVOIR BASINWIDE Number of Reservoirs Current Last Year Average Capacity (KAF) (KAF) (KAF) (KAF) 49.4 58.0 42.9 62 7.7 7.6 7.2 11 0.0 0.0 0.0 40 0.0 0.0 30.7 150 6.2 0.0 3.6 7 27.0 0.0 12.0 27 291.6 120.1 135.9 616 8.9 6.9 4.1 9 37.2 33.8 22.9 42 262.8 226.9 187.5 354 39.3 24.4 25.6 167 92.7 66.3 86.3 127 34.9 45.1 54.3 86 857.8 589.0 613.0 1698.8 13 13 13 13 ARKANSAS RIVER BASIN Water Supply Forecasts February 1, 2018 Forecast Exceedance Probabilities and Volumes Forecast Forecast Drier Future Conditions Wetter POW Period Box labels on chart are volumes of water in thousand acre-feet. Chalk Ck nr Apr-Jul 6.6 11 19 26 Nathrop Apr-Sep 8.8 14 I 23 31 ArkansasRat Apr-Jul 129 165 - 220 270 Salida Apr-Sep 161 205 - 275 335 Grape Ck nr Apr-Jul 0 6.7 13 Westcliffe Apr-Sep 0.01 1.6 8 16 ArkansasRab Apr-Jul 131 197 I 310 410 Pueblo Apr-Sep 186 265 400 515 HuerfanoRnr Apr-Jul 1.5 3.1 I 6 Redwing Apr-Sep 2.5 4.5 - 8.1 CucharasRnr Apr-Jul 0.48 - 2 5.9 10 La Veta 1 3 7.5 12 Trinidad Lake Apr-Sep 2.1 8.6 24 41 8.8 Apr-Sep In?ow Mar-Jul 1100 110 120 130 Percent of Average (30 Yr Period) 10% Exceedance 30% Exceedance 50% Exceedance 70% Exceedance 90% Exceedance Forecast (KAF) Forecast (KAF) Forecast (KAF) Forecast (KAF) Forecast (KAF) El 0 There is a 30% chance that There is a 50% chance that There is a 70% chance that El 0 Exceedance flows will exceed this volume. ?ows will exceed this volume. ?ows will exceed this volume. 95" Exceedance UPPER RIO GRANDE RIVER BASIN February 1, 2018 Snowpack in the Upper Rio Grande River basin is below normal at 31% of median. Precipitation for January was 50% of average which brings water year-to-date precipitation to 38% of average. Reservoir storage at the end of January was 123% of average compared to 90% last year. Streamflow forecasts range from 59% of average for the inflow to Platoro Reservoir to 22% of average for Sangre de Cristo Creek. Upper Rio Grande Basin Mountain Snowpack Snow Water Equivalent (Inches) 25 20 15 10 5 Historic Snowpack Range Median Snowpack *SWE values calculated using daily SNOTEL data only Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov Oct 0 50% Exceedance Mountain Precipitation 60 Percent of Average 50 40 30 20 10 0 Oct Nov Dec Monthly Jan Feb Mar Year-to-date April May Watershed Snowpack Analysis February 1st, 2018 Sub-Basin Alamosa Creek Conejos & Rio San Antonio Culebra & Trinchera Creek Upper Rio Grande Basin-Wide Total Last Year % # of Sites % Median Median 3 32 162 4 39 173 6 31 169 10 28 146 22 31 160 *SWE values calculated using first of month SNOTEL data and snow course measurements Reservoir Storage Percent Average 300% Percent Capacity 250% 200% 150% 100% 50% 0% CONTINENTAL RESERVOIR PLATORO RESERVOIR RIO GRANDE RESERVOIR SANCHEZ RESERVOIR SANTA MARIA RESERVOIR Reservoir Storage End of January 2018 Reservoir CONTINENTAL RESERVOIR PLATORO RESERVOIR RIO GRANDE RESERVOIR SANCHEZ RESERVOIR SANTA MARIA RESERVOIR TERRACE RESERVOIR BEAVER RESERVOIR BASINWIDE Number of Reservoirs Current Last Year Average Capacity (KAF) (KAF) (KAF) (KAF) 11.4 9.0 4.5 27 23.2 15.6 24.0 60 27.0 24.8 16.3 51 21.1 9.2 27.6 103 18.9 16.5 10.5 45 8.3 4.9 6.2 18 3.8 3.1 4.2 5 113.6 83.1 93.3 308.5 7 7 7 7 TERRACE RESERVOIR BEAVER RESERVOIR BASINWIDE 1 UPPER RIO GRANDE BASIN Water Supply Forecasts February 1, 2018 Forecast Exceedance Probabilities and Volumes Forecast Forecast Drier Future Conditions Wetter Point Period Box labels on chart are volumes of water in thousand acre-feet. RioGrandeat Apr-Jul Thirty Mile Bridge Apr-Sep 36 53 - so 104 Rio Grande at Apr-Sep 86 132 I 210 275 Wagon Wheel Gap SF Rio Grande Apr-Sep South Fork Rio Grande nr Apr-Sap 130 199 I 320 420 Del Norte SaguacheCknr Apr-Sep 7.1 13 i 24 34 Saguache AlamosaCkab Apr-Sap 19 28 - 41 53 Terrace Reservoir LaJaraCknr Mar-Jul 1.6 2.8 I 5.1 7.2 Capulin Trinchera Ckab Apr-Sap 2.4 3.7 - 5.8 7.8 Turners Ranch Sangre De Apr-Sep 0.29 1.8 I 6 11 Ck UteCkanort Apr-Sap 1.7 3.5 7.1 11 Garland Platoro Apr?Jul 21 28 - 38 47 Reservoir Inflow Apr-Sep 23 - 30 - 42 52 ConejosRnr Apr-Sep 60 84 - 123 156 Mogote San AntonioRat Apr-Sep ?0.47 1.8 - 4.9 8.1 Ortiz LosPinosRnr Apr-Sep 12 20 - 35 47 Ortiz Culebra Ckat Apr-Sep 2.1 - 4.9 11 16 San Luis Costilla Mar-Jul 2.5 4 I 6.6 8.9 Costilla Dam CostillaCknr Mar-Jul 2.9 6 I 12 18 Costilla 100 110 120 Percent of Average (30 Yr Period) 10% Exceedance 30% Exceedance 50% Exceedance 70% Exceedance 90% Exceedance Forecast Forecast Forecast Forecast Forecast There is a 30% chance that There is a 50% chance that There is a 70% chance that 5% Exceedance . . 0 flows exceed this volume. flows exceed this volume. flows exceed this volume. 95 4' Exceedance SAN MIGUEL, DOLORES, ANIMAS, AND SAN JUAN RIVER BASINS February 1, 2018 Snowpack in the combined southwest river basins is below normal at 34% of median. Precipitation for January was 55% of average which brings water year-to-date precipitation to 29% of average. Reservoir storage at the end of January was 105% of average compared to 115% last year. Current streamflow forecasts range from 56% of average for the inflow to Lilylands Reservoir to 33% for the La Plata River near Hesperus. San Miguel, Dolores, Animas & San Juan River Basins Mountain Snowpack Snow Water Equivalent (Inches) 35 30 25 20 15 10 5 Historic Snowpack Range Median Snowpack Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov Oct 0 50% Exceedance *SWE values calculated using daily SNOTEL data only Mountain Precipitation 60 Percent of Average 50 40 30 20 10 0 Oct Nov Dec Monthly Jan Feb Mar Year-to-date April May Watershed Snowpack Analysis February 1st, 2018 Sub-Basin Animas Dolores San Miguel San Juan Basin-Wide Total Last Year % # of Sites % Median Median 10 36 180 7 37 185 6 34 170 4 30 157 25 34 174 *SWE values calculated using first of month SNOTEL data and snow course measurements Reservoir Storage Percent Average 140% Percent Capacity 120% 100% 80% 60% 40% 20% 0% GROUNDHOG RESERVOIR JACKSON GULCH RESERVOIR LEMON RESERVOIR MCPHEE RESERVOIR NARRAGUINNEP RESERVOIR Reservoir Storage End of January 2018 Reservoir GROUNDHOG RESERVOIR JACKSON GULCH RESERVOIR LEMON RESERVOIR MCPHEE RESERVOIR NARRAGUINNEP RESERVOIR VALLECITO RESERVOIR TROUT LAKE RESERVOIR BASINWIDE Number of Reservoirs Current Last Year Average Capacity (KAF) (KAF) (KAF) (KAF) 12.2 18.1 12.4 22 5.2 5.1 4.5 10 18.6 20.6 20.9 40 284.5 294.4 266.4 381 11.7 15.5 14.7 19 67.3 84.3 63.3 126 2.6 3.2 2.1 3 402.2 441.3 384.3 601.2 7 7 7 7 VALLECITO RESERVOIR TROUT LAKE RESERVOIR BASINWIDE 1 SAN JUAN RIVER BASINS Water Supply Forecasts February 1, 2018 Forecast Exceedance Probabilities and Volumes Forecast Forecast Drier Future Conditions Wetter Point Period Box labels on chart are volumes of water in thousand acre-feet. DoloresRat Apr-Jul 52 83 I 137 185 Dolores Dolorestl Apr-Jul 49 86 I 154 215 Mcphee Reservoir San MigueIRnr Apr-Jul 32 50 80 107 Placerville Cone Reservoir Apr-Jul 0.78 1.2 I 1.9 2.5 Inlet GurleyReservoir Apr-Jul 5.5 7.4 - 10 13 Inlet Lilylands Apr-Jul 0.6 1.1 2 2.8 Reservoir Inlet RioBlancobl Apr-Jul 14 22 I 35 46 Blanco Diversion NavajoRatOso Apr-Jul 17 26 I 41 55 Diversion San Juaanr Apr-Jul 80 131 I 220 300 Carracas PiedraRnr Apr-Jul 31 53 - 93 130 Arboles Los PinosRnr Apr-Jul 47 68 - 103 133 Bay?eld San Juaanr Apr-Jul 106 - 179 - 310 430 Archuleta Animas Rat Apr-Jul 100 145 - 220 285 Durango FIoridaRbI Apr-Jul 9.4 15 - 25 34 Lemon Reservoir nr Apr-Jul 3.4 5.7 9.9 14 Hesperus MancosRnr Apr-Jul 4 7.7 I 15 21 Mancos 100 110 Percent of Average {30 Yr Period) 10% Exceedance 30% Exceedance 50% Exceedance 70% Exceedance 90% Exceedance Forecast (KAF) Forecast (KAF) Forecast (KAF) Forecast (KAF) Forecast (KAF) There is a 30% chance that There is a 50% chance that There is a 70% chance that El 0 5 1? Exceedance flows will exceed this volume. flows will exceed this volume. flows will exceed this volume. 95 Exceedance How to Read Snowpack Graphs The graphs show snow water equivalent (SWE) (in inches), using daily SNOTEL data. for the October 1 through September 30 water year. Basin “observed” SWE values are computed using SNOTEL sites which are characteristic of the snowpack of the particular basin. The SWE observations at these sites are averaged and normalized to produce these basin snowpack graphs. Current water year is represented by the heavy red line terminating on the last day the graphic was updated. Historical observed percentile range is shown as a gray background area on the graph. Shades of gray indicate maximum, 90 percentile, 70 percentile, 50 percentile (solid black line), 30 percentile, 10 percentile, and minimum for the period of record. 50 % Excedance Projection: The most probabilistic snowpack projection, based on the median snowpack is projected forward from the end of the current period to the end of the current water year. For more detailed information on these graphs visit: http://www.nrcs.usda.gov/Internet/FSE_DOCUMENTS/nrcs144p2_062291.pdf South Platte River Basin Mountain Snowpack Historical Observed Percentiles: Maximum (on top), 90, 70, 50 (median), 30, 10, Minimum (on bottom). 25 20 15 50 % Exceedance Projection 10 5 Historic Snowpack Range Median Snowpack Current Snowpack Sep Aug Jul Jun May Apr Mar Feb Jan Dec Nov 0 Oct Snow Water Equivalent (Inches) 30 50% Exceedance How Forecasts Are Made For more water supply and resource management information, contact: Brian Domonkos Snow Survey Supervisor USDA, Natural Resources Conservation Service Denver Federal Center, Bldg 56, Rm 2604 PO Box 25426 Denver, CO 80225-0426 Phone (720) 544-2852 Website: http://www.nrcs.usda.gov/wps/portal/nrcs/main/co/snow/ Most of the annual streamflow in the western United States originates as snowfall that has accumulated in the mountains during the winter and early spring. As the snowpack accumulates, hydrologists estimate the runoff that will occur when it melts. Measurements of snow water equivalent at selected manual snow courses and automated SNOTEL sites, along with precipitation, antecedent streamflow, and indices of the El Niño / Southern Oscillation are used in computerized statistical and simulation models to prepare runoff forecasts. Unless otherwise specified, all forecasts are for flows that would occur naturally without any upstream influences. Forecasts of any kind, of course, are not perfect. Streamflow forecast uncertainty arises from three primary sources: (1) uncertain knowledge of future weather conditions, (2) uncertainty in the forecasting procedure, and (3) errors in the data. The forecast, therefore, must be interpreted not as a single value but rather as a range of values with specific probabilities of occurrence. The middle of the range is expressed by the 50% exceedance probability forecast, for which there is a 50% chance that the actual flow will be above, and a 50% chance that the actual flow will be below, this value. To describe the expected range around this 50% value, four other forecasts are provided, two smaller values (90% and 70% exceedance probability) and two larger values (30%, and 10% exceedance probability). For example, there is a 90% chance that the actual flow will be more than the 90% exceedance probability forecast. The others can be interpreted similarly. The wider the spread among these values, the more uncertain the forecast. As the season progresses, forecasts become more accurate, primarily because a greater portion of the future weather conditions become known; this is reflected by a narrowing of the range around the 50% exceedance probability forecast. Users should take this uncertainty into consideration when making operational decisions by selecting forecasts corresponding to the level of risk they are willing to assume about the amount of water to be expected. If users anticipate receiving a lesser supply of water, or if they wish to increase their chances of having an adequate supply of water for their operations, they may want to base their decisions on the 90% or 70% exceedance probability forecasts, or something in between. On the other hand, if users are concerned about receiving too much water (for example, threat of flooding), they may want to base their decisions on the 30% or 10% exceedance probability forecasts, or something in between. Regardless of the forecast value users choose for operations, they should be prepared to deal with either more or less water. (Users should remember that even if the 90% exceedance probability forecast is used, there is still a 10% chance of receiving less than this amount.) By using the exceedance probability information, users can easily determine the chances of receiving more or less water. Interpreting the Forecast Graphics These graphics provide the same information that was contained in the previously published basin forecast tables, but provide a new way to visualize the range of streamflows represented by the forecast exceedance probabilities for each forecast period. The numbers displayed in the box represent the actual forecasted streamflow volume (in KAF) for the given exceedance probability, and the horizontal position of the box represents the percent of average of that streamflow volume. The spread of the forecasts offers an indication of the uncertainty in a given forecast; when the colored boxes are spread far a part, the forecast skill is low and uncertainty is high; when the boxes are close together, the forecast skill is higher and uncertainty lower. OF WATER BEGINS WITH THE SHOW SURVEY Denver Federal Center, 56, Rm 2604 PO Box 25426 Denver, CO 80225-0426 In addition to the water supply outlook reports, water supply forecast information for the Western United States is available from the Natural Resources Conservation Service and the National Weather Service January through June. The information may be obtained from the Natural Resources Conservation Service web page at Issued by Released by Leonard Jordan Clint Evans Acting Chief State Conservationist Natural Resources Conservation Service Natural Resources Conservation Service U.S. Department of Agriculture Lakewood, Colorado Colorado Water Supply Outlook Report Natural Resources Conservation Service Lakewood, CO