CWCB March 2018 Drought Update

March Drought Map, 2018

Despite near normal precipitation across most of the state in February, March precipitation has been well below average statewide. Currently Colorado is experiencing the 3rd lowest snowpack on record, with only 2002 and 1981 being drier. Extreme drought has expanded to cover most of Southwestern Colorado, The San Luis Valley and Southeastern Colorado. West Slope providers with limited storage are concerned about the demand season and thinking about possible restrictions, while Front Range providers are thinking about conservation messaging.

 As of March 23rd, statewide snowpack at SNOTEL sites is 69 percent of average. The North and South Platte basins have experienced the highest levels of precipitation in the state, at 90 and 81 percent, respectively. While the Yampa & White and Colorado River Basins are slightly lower at 80 percent. The southern half of the state has been significantly drier with the Southwest basins of the San Miguel, Dolores, Animas & San Juan, Rio Grande, Gunnison and Arkansas all well below normal precipitation at 54, 54, 61 and 58 percent respectively.

 Many basins’ year –to-date precipitation, based on SNOTEL is tracking near 2002, as is the state as a whole.   74 percent of the state is in some level of drought classification with 24 percent in moderate drought, 30 percent in severe drought and 20 percent classified as extremely dry. An additional 16 percent of the state is experiencing abnormally dry conditions (see image on reverse side).

 Reservoir storage statewide is at 116 percent of normal, with all basins above average. The Arkansas basin is reporting the highest average storage at 145 percent. The Southwest basins of the San Miguel, Dolores, Animas & San Juan have the lowest storage levels in the state at 105 percent of normal.

 The Surface Water Supply Index(SWSI) values improved slightly for March 1, but remain below normal with much of the western slope classified as moderate to extremely dry. These values are expected to decline when new numbers are released on April 1, this is largely the due to below average streamflow forecasts.

 Streamflow forecasts are well below average for the vast majority of the state and near normal in isolated areas including the Blue River, St. Vrain and Cache La Poudre basins.

 Short term forecasts show that temperatures will be more seasonal with a normal chance of precipitation, however longer term forecasts indicate increased likelihood of below average precipitation and above average temperatures.

 A weak La Niña remains active and is projected to transition to neutral conditions in May or June, indicating that warm and dry conditions are likely to persist through the spring. While the monsoonal rainfall forecast is still uncertain, above average temperatures should continue into the summer months.

Statewide SNOTEL snowpack is well below average at 69 percent of normal, and tracking close to 2002 levels. To reach a normal snowpack peak we would need to 480 percent of normal accumulation. Snowpack typically peaks in early to mid April.

Southern Colorado has continued to see an expansion of drought conditions through the snow accumulation season, while moderate and severe drought has also expanded across the northern half of the state.

March 1 streamflow forecasts are below 60 percent of average for nearly all of southern Colorado, while the central portion of the state ranges from 70-80 percent of average. With dry conditions throughout March the April 1 streamflow forecasts are projected to decline.