The 2020 Water Year, running from Oct. 1, 2019 to Sept. 30, 2020, ended with a total of 31.51 inches of precipitation in Iowa. This period of time is used by hydrologists since Oct. 1 marks the end of the growing season, and precipitation after that date becomes a source of runoff into streams for the next calendar year. Temperatures in this time averaged 48.6 degrees, which is 0.5 degrees above normal for Iowa.
A majority of Iowa received below normal precipitation over the 2020 Water Year, with only northeastern Iowa receiving above-average totals of 3 to 9 inches. For the remaining portions of the state, precipitation deficits dominated, especially in western Iowa, where totals were between 10 to 18 inches below normal.
“Conditions continue to become drier as we move into the fall months,” said Tim Hall, DNR’s coordinator of hydrology resources. “This causes some concern as we see decreases in average rainfall from October into November. Replenishing soil moisture and groundwater becomes more challenging as we move toward the winter months.”
The current drought monitor map, which reflects conditions as of Oct. 6, shows a return of extreme drought conditions. About 5 percent of the state is rated in extreme drought, while conditions have been moved from moderate drought into severe drought in other parts of northwest and western Iowa. Overall, the area of Iowa covered by some form of dryness or drought has not changed in the last month.
Temperatures were generally cooler across Iowa during September, with a statewide average temperature of 61.9 degrees, 1.3 degrees below normal. Spencer Municipal Airport (Clay County) reported the month’s high temperature of 96 degrees on Sept. 6, 18 degrees above normal. Mason City Municipal Airport (Cerro Gordo County) reported the month’s low temperature of 35 degrees on Sept. 18, 12 degrees below normal.
After the third driest August on record, widespread rainfall returned to Iowa during September. The statewide average precipitation totaled 4.06 inches, or 0.68 inches more than the 30-year average. Much of the eastern two-thirds of Iowa reported above average precipitation totals with the highest amounts occurring in eastern Iowa; 4 to 6 inches of above average rainfall were recorded across more than 10 counties. On the other side of the state, precipitation deficits from 1 to 2 inches were found. Northwest Iowa observed the driest conditions of 2 or more inches below normal.
For a thorough review of Iowa’s water resource trends, go to www.iowadnr.gov/
The report is prepared by technical staff from Iowa DNR, the Iowa Department of Agriculture and Land Stewardship, IIHR—Hydroscience and Engineering, and the U.S. Geological Survey, in collaboration with Iowa Homeland Security and Emergency Management Department.