Iowa has had an unusually dry first quarter, according to a water summary update released last week by the Iowa Department of Natural Resources.
Average precipitation statewide has been just 2.76 inches as of April 7, marking this the driest start to a year in Iowa since 1994, the DNR states. On average, Iowa typically sees 4.77 inches of precipitation by April 7.
“This continues the relatively dry weather pattern that began in mid-October in central and southwestern Iowa, and in July 2014 across much of northern/northeastern Iowa,” the report states. Recent rainfall and a cool growing season in 2014 has led soil moisture — a significant contributing factor in flooding — to exceed levels seen over the last three years, however.
Despite this, the National Weather Service predicts flooding in Iowa through early June will remain “near normal,” due to low levels of precipitation across the state. A normal risk of flooding means that some amount of flooding may occur, as is typical for the state of Iowa, but it is unlikely to be severe based on current projections.
Drought conditions are particularly severe in northwest and eastern Iowa, according to the report. Streamflow conditions and groundwater levels in eastern and northwest Iowa are also below average.
Tim Hall, Hydrology Resources Coordinator at the Iowa DNR, notes that this report does not take flash floods into consideration, as they are typically localized and specific to individual storm systems. To predict flooding in a more general sense, experts look at several factors leading into the spring and summer.
“For most of the interior part of the state of Iowa, [flooding] has to do with soil moisture and precipitation,” Hall said. “The other thing that tends to play in a little bit is temperature.” Hall notes that in warmer temperatures, crops and vegetation pull more moisture out of the soil, lowering soil moisture levels and exacerbating drought-like conditions.
“Drought tends to be a combination of temperature and rainfall,” Hall added. “Most people just think about the rainfall side.”
The water summary update came just prior to heavy rainfall across the state, which “should help,” according to the report. The department plans on releasing updates every two weeks through the rest of this spring and summer.
The report was compiled by the Iowa DNR in collaboration with the Iowa Department of Agriculture and Land Stewardship, the U.S. Geological Survey, IIHR–Hydroscience and Engineering and The Iowa Homeland Security and Emergency Management Department.