Good news—so far—regarding soil moisture
Normally the start to the calendar year in Iowa provides little in the way of significant precipitation. This year, however, two rain/snow events produced some localized flooding, and helped to alleviate some of the dry conditions that have been present in the state since last fall. The first two months of the year produced 2.7 inches of moisture, more than 0.7 inches above normal. As a result, streamflow has increased to normal over most of Iowa, and shallow groundwater conditions are improving. There remains an area of concern in Southeast Iowa, where the drought monitor shows about 10 percent of the state in a condition of Moderate Drought. Some parts of Southeast Iowa are short over 20 inches of rainfall over the past two years.
Over the last two months conditions across the state have seen some improvement. The Drought Severity and Coverage Index (DSCI) was developed to provide a way to compare regional conditions over time, and has been dropping in Iowa. The DSCI now stands at 37, down from nearly 80 at the beginning of the year. This shows the gradual improvement in drought conditions over the winter months. Areas of southeast Iowa continue to be of concern, with nearly all of 10 counties rated in D1-Moderate Drought; a total of 10 percent of the state. This is an improvement over the conditions that existed on October 1 of last year, when over 30 percent of the state was rated D1 and six percent of the state was rated in D2—Severe Drought. Regionally, considerable improvement to conditions has occurred in Missouri and Arkansas, while significant dryness and drought continues in much of the Southwest and in the Dakotas.
CURRENT STREAM FLOW:
Streamflow conditions in much of the state remain in the normal range. Northeast Iowa moved from the normal flow in January to above normal flow in February. Flow in portions of the Thompson and Chariton River basins has been below normal condition for the past two months. Streamflow conditions that were above normal in January for several basins in the western portion of the state have decreased to the normal flow. ISGS crews have been making extra site visits to verify ice conditions on the streams as well as collecting additional streamflow measurements to validate real-time values. It should be noted that during the winter season, USGS streamflow data may be impacted by ice formation and backwater. This information should be used as preliminary information only.
Soils were frozen across nearly all of Iowa through most of January and February, with the exception of a few brief periods when the uppermost few inches of soils thawed over portions of southern Iowa. However, soils were completely thawed by the end of February over much of the southern one-third of the state, with thawing of much of the topsoil across the central one-third of Iowa.
Shallow groundwater conditions have improved over most of the northwest, southwest and northeast Iowa during the first two months of 2018. Shallow groundwater conditions in parts of south central and southeast Iowa remain in a slight to moderate drought classification. Additional spring rainfall is needed across the southern half of Iowa to improve shallow groundwater conditions.
Subsoil remains very dry over much of south central and southeast Iowa, where both 2016 and 2017 were unusually dry with 24-month precipitation deficits exceeding 20 inches, in some areas.
On March 1, the National Weather Service (NWS) issued its final spring flood outlook. The outlook calls for Update, peace contact any of the following:
General Information: Tim.Hall@dnr.iowa.gov, 515-725-8298; Drought Monitor/Precipitation: Harry.Hillaker@iowaagriculture.gov, 515-281-8981; Stream Flow: Daniel Christiansen, firstname.lastname@example.org, 319-358-3639, or Michael.Anderson@dnr.iowa.gov, 515-725-0336; Shallow Groundwater: email@example.com, 319-335-1581; and, Flood Outlook: firstname.lastname@example.org, 515-270-4501.