Drying, Warming Soils across Illinois

[September 21, 2018]    Soils are drying out after the early September rain, according to Jennie Atkins, Water and Atmospheric Resources Monitoring (WARM) Program manager at the Illinois State Water Survey, University of Illinois.

Illinois has received 3.61 inches of rain as of Sept. 13, 2.31 inches more than normal. Most parts of the state are seeing a wetter than usual month, and soil moisture levels across the state have been affected. Levels at 2 inch depths averaged 0.33 water fraction by volume (wfv) on Sept. 13, 120 percent greater than in 2017.

Soils have been drying during the second week of September, with moisture declining 20 percent from the highs of last weekend. However, moisture levels remain high, especially in parts of southern Illinois where levels are above field capacity.

Soil moisture is also declining at depths from 4 to 20 inches after increases from earlier rain events. Levels at 39 and 59 inches remain high but steady.

Soil temperatures are increasing in mid-September. The month began with higher than normal temperatures due to the warmer weather, but cooled off as the remnants of tropical storm Gordon passed through the state. Soils have been warming the second week of the month.

Temperatures at 4 inches under sod averaged 73.2 degrees on Sept. 13, up 2.5 degrees from the monthly low on Sept. 9, but 6.1 inches lower than the month’s high on Sept. 5. Temperatures are increasing at all depths with mid-month averages ranging from 72.1 degrees at 8 inches under sod to 75.8 degrees for 2 inches under bare soil.

The Illinois State Water Survey’s WARM Program collects hourly and daily weather and soil information at 19 stations across the state. Daily and monthly summaries can be found at the WARM website http://www.isws. illinois.edu/warm/ and in the Illinois Water and Climate Summary http:// www.isws.illinois.edu/warm/climate.asp. 

[Lisa A. Sheppard]