Midwest snowfall could bring drought relief to Mississippi River basinView Source
Several winter storms have barreled through the Midwest since the start of the year, bringing deep snow and bitter cold. In Iowa, where treacherous roads caused hundreds of accidents, snowpack grew up to 20 inches in some places — marking a winter with 180% more precipitation than normal, so far.
Last week’s storm reached all the way down to Memphis, where the mayor declared a state of emergency after six inches of snow snarled traffic, and freezing temperatures caused at least two deaths. Meantime, schools and offices were closed as far south as Baton Rouge and New Orleans, due to several days of sub-zero weather.
The snow comes on the heels of several years of drought that has left parts of the Mississippi River basin with rainfall deficits of a foot-plus.
This week, higher temperatures should melt some of the recent snow and ice. As it melts, that water will bleed into parched waterways in Iowa and beyond, helping restore stream flows decimated by drought. It could also carry the risk of flooding downstream.
Most of Minnesota and northern Wisconsin are seeing below-average snowpacks — a sharp contrast to last year when historic snow led to flooding on the Mississippi River. The rest of the Midwest, however, is inundated with above-average snowpack. Around a foot of snow blankets eastern Nebraska into northern Illinois and southern Wisconsin.
Drought conditions don’t typically improve in the winter, as frozen soils can’t soak up precipitation. But the warmer-than-normal December allowed rainfall to infiltrate soils across the western Corn Belt. Parts of Iowa received more than double the month’s average rainfall, and drought conditions have improved in western Minnesota, Kansas and Missouri.
“That was really beneficial because soils were not frozen yet,” said Dennis Todey, director of the U.S. Department of Agriculture’s Midwest Climate Hub. “A lot of that was able to soak into the soil.”
The winter storms that passed through the Midwest even tossed some rain to some parts of the basin, particularly in southern Illinois and Missouri, before the ground froze.
Winter weather advisories are in effect throughout the upper Mississippi River basin, and freeze warnings and watches span the lower basin. Much of the ground is frozen in the Midwest, so soils can’t absorb expected snowmelt this week. But the water can help in another way: It can feed into parched waterways across the basin.
Last summer’s drought brought cascading impacts across the basin, including saltwater intrusion that threatened drinking water in New Orleans, ongoing marsh fires in Louisiana and upriver challenges for agriculture and shipping.
Farmers reported difficulties getting water to their cattle last year. Public water supplies had to fall back on emergency procedures as their resources dwindled, like in Iowa where a community considered using recycled wastewater as drinking water.
“We’re lacking water in a lot of places,” Todey said. “Soils are dry. Aquifers are dry. Ponds, lakes, rivers are all very dry. So runoff is beneficial.”
Overnight lows should stay below freezing for much of the Midwest this week, which will preserve some of the snowpack and prevent widespread flooding.
The melt may lead to some ice jams — when clumps of river ice back up flow — and localized flooding in the upper Mississippi River basin. But, generally, waterway levels are low enough to handle more water.
“That’s one thing with this drought: We can take an inundation of water in the inland streams and also the rivers,” said state climatologist Justin Glisan.
But the lower part of the Mississippi River basin, south of Cairo, Illinois, is not likely to see much relief from snowfall in the Midwest after months of drought.
Louisiana State University professor and former state climatologist, Barry Keim, said “it’s a drop in the bucket.” However, he said the unseasonably cold weather in the South is bringing a different form of drought relief: Because the moisture is frozen in the soil, the ground can’t dry out even more.
Meteorologists are hoping soil moisture levels throughout the region may see some relief come spring. As the El Nino weather pattern continues through the rest of winter, the upper U.S. could expect warmer temperatures and more active storms over the next six weeks.
“We have some huge rainfall deficits that have built up, not only over the last year but the last few years,” Todey said. “We want to see some improvements in those deficits before we start talking about a lot of drought improvement.”