Streamflows Up; More Rain Predicted

Streamflows Up; More Rain Predicted

April 27, 2007

Significant storm activity during the past week dropped record rainfall across much of the state east of the Panhandle. Rainfall totals from the April 23-25 storm were impressive, with levels of 2-3 inches common and isolated reports of 6 inches reported across the southern third of Nebraska. Preliminary analysis indicates that all time 24-hour precipitation records for April 24 were set at almost every location east and southeast of a line from McCook to Norfolk.

Graphic illustrating precipitation in inches for seven days, ending April 26.
Figure 1. Precipitation in inches for the last seven days, ending April 26, for the High Plains Region. For more maps and data on Nebraska precipitation and soil temperature, visit the CropWatch Weather.

Unfortunately, much of the northern half of the Panhandle missed out on the generous precipitation. The Panhandle remains the only area within the state that is still designated by the U.S. Drought Monitor as experiencing at least moderate drought conditions. Severe to extreme drought conditions exist for areas north of a line from Scottsbluff to Alliance.

The excessive moisture has led to rapid increases in streamflow rates within the Republican, Loup, Elkhorn and Platte (east of North Platte) river basins. Within the Republican River basin numerous locations received 3-6 inches of moisture, with streamflow rates increasing 10-15 fold within a 24-hour period. This surge of water will add additional storage to Harlan County reservoir, but the exact impact is still unknown.

The wild roller coaster ride of weather during April has begun to impact spring corn planting across the entire Corn Belt. Very cold temperatures during the first two weeks of April inhibited normal surface drying, only to be followed by a brief period of warm temperatures before the onset of excessive precipitation. It will probably take at least four to five days of above normal temperatures and no precipitation for fields to dry enough to allow planting to resume.

As of April 22, the five largest corn producing states (Iowa, Illinois, Nebraska, Indiana and Ohio) all reported that corn planting was behind last year and the five-year average. Last year, Iowa and Illinois had planted 23% and 29% of their corn crop, respectively, compared to only 8% and 13% this year. The five-year average for Iowa is 18%, while Illinois is 37%. Nebraska stands at 9% planted, compared to 14% last year and the five-year average of 11%. Indiana and Ohio are in worse shape with only 4% of their corn crop in the ground.

After a welcome warm-up this weekend and early next week, another potent storm system appears to be headed toward the central and northern Plains region. Precipitation could begin as early as May 2, with continual chances for moisture through at least May 10. Right now the models point to heavy moisture events May 3-4, 6-7 and 9-10. If the forecasts prove true, significant corn planting delays could continue through at least mid-May.

Streamflow Rates

The recent storm brought welcome moisture and heavy snowfall to central Colorado, but missed much of Wyoming. Snowpack levels continued to decrease in much of the head water region of the northern branch of the Platte River. Sites in the North Platte River basin are at 40-80% of normal and have declined for nearly eight consecutive weeks.

Additional supplements to streamflow rates this summer will need to come from excessive precipitation events and/or above normal precipitation during much of the growing season. The U.S. Drought Monitor forecasts improving conditions within the Nebraska Panhandle, but little improvement within upper northern Platte basin of Wyoming. In addition, the Climate Prediction Center projects that much of Colorado and Wyoming will have below normal moisture in May and June.

Al Dutcher
Extension State Climatologist, Lincoln

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A field of corn.