Spring moisture needed for drought recovery
August 11, 2015
April showers bring May flowers, or so they say. Spring showers also bring one very important element to the state of Colorado, and that is much needed moisture.
Spring time is a time of year that the ground can absorb moisture without a high risk of evaporation. In years following a drought, this moisture is more important than ever to the path of drought recovery.
In general, February is too early for moisture to make a big difference. The ground still has a layer of frost, and moisture is unable to penetrate the soil.
"Mid-winter moisture doesn't usually add that much to soil moisture in the Eastern plains because the ground if often still frozen. It was great having moisture at the end of February, however, because some of our best improvements happen in March and April," said Nolan Doesken, Colorado State Climatologist.
He continued, "We need to get things off to a good start, and the moisture and cool weather is better. Anything that keeps vegetation dormant, and not pulling moisture and reducing evaporation rates, is a good thing. We need to stay in winter mode. It's better for drought recovery."
For the month of February, Colorado did not receive normal moisture, even with the storms. "Last month, most of the Upper Colorado River Basin received less than average precipitation. Through the higher elevation, precipitation amounts exceeded 1-inch in most areas, much of the UCRB received between 20 percent and 90 percent of average moisture for February. Part of southwest Colorado and southwest Wyoming received near to slightly above average precipitation for the month," said Becky Smith, Drought Specialist and Graduate Research Assistant at Colorado State University in the NIDIS Weekly Climate, Water and Drought Assessment Summary dated March 5.
Snowpack in the mountains in an important indicator of drought, and so far, Colorado is behind. "Water-year-to-date SNOTEL precipitation percentiles in the UCRB are below the median throughout the entire basin. The northern and central Colorado mountain are below the 20th percentile at most locations, with several sites recording below the 5th percentile. Percentile rankings in southwest Colorado in the San Juan mountains are mostly in the teens," said Smith.
She continued, "Accumulated snowpack is currently less than normal across the entire UCRB. Sub-basins in western Colorado range between 74 percent to 81 percent of normal snowpack. The northeast Utah and southwest Wyoming basins, which had been closer to normal for most of the water year, are now a little lower, ranging from 75 percent of normal to 87 percent of normal for the season."
Temperatures in February have been cold, which is good in terms of keeping vegetation dormant. "Last month, the entire UCRB saw below average temperatures ranging between three and nine degrees colder than average. East of the basin, the rest of Colorado experienced slight below average temperatures for February. Last week, the entire region saw temperatures ranging from three to 12 degrees colder than average."
Reservoir volume is also important in drought recovery. "Last month, most of the major reservoirs in the UCRB saw slight decreases in volume, which is normal for this time of year. Blue Mesa has stayed near steady for most of the calendar year though it usually decreases this time of year. McPhee decreased in volume, though it normally increases slightly in February. Lake Granby saw large volume decreases last month. Flaming Gorge is the only major reservoir near its March average. The rest of the major reservoirs range between 55 percent and 90 percent of average for the month of March," Smith stated.
Going forward, Doesken feels optimistic about the state's chances for moisture. "The predictions made for the spring months have not been favorable all through the winter. Most likely, but not for certain, it will be warmer than average and dryer than average. However, with that being said, the storm track has been active, and we have had a steady sequence of storms. Overall, there is a much more optimistic outlook for spring than we had a few weeks ago," he said.
The importance of the spring storms in the next few weeks will be vital to recovery. "The next storm is the most optimistic for Northeast Colorado into Nebraska. March storms do so much good. The soil has less frost, so that moisture is more likely to go into the soil. We need the moisture first, before we get the wind. That makes a big difference. It's always a waiting game for spring moisture and spring winds"
Moisture would greatly help the state, but because of the drought, it will be an uphill battle. "My biggest concern is the fact that we were deep enough in the hole from last year over the entire state: forests, mountains, reservoirs, dryland and irrigated regions. We ended the year with such dry soils, that we know that we are considerably vulnerable going into this year," said Doesken.
He continued, "Spring is such a critical season. It's our best chance of recovery, and easiest time to slip deeper into drought. It's a long path to recovery, but have made a good run so far, and there is general optimism. However, everything hinges on these next few weeks. The moisture would be a wonderful inconvenience." ❖