High River Levels in Winter

River levels are abnormally high for this time of year across much of the Upper Mississippi River Valley region. Although many rivers are either observing ongoing flooding, or are still forecast to reach flood levels, river flooding is not a normal phenomenon during the winter months. There are 2 main reasons for this:

The winter months are typically the drier months of the year
Precipitation typically falls as snow, which endurs a slow runoff rate into the rivers.

Antecedent conditions play a large part in why river levels will reach flood stage. Multiple heavy rain events have occurred in this winter, with much of the area also seeing one instance of heavy snow. Following the snow, warm temperatures caused a quick melt of the snow, and with the additional rains the ground has become very saturated. This means when it rains the water will runoff into the rivers rather than soaking into the ground. This would be similar to what happens with rain that falls on concrete, or on frozen ground.

The amount of rain that has fallen so far in December far exceeds the amounts that are normal for this time of year. The images below show the rainfall totals from December 13 & 14 and the departure from normal of precipitation for the month of December (through December 17th). This shows that much of Iowa and Wisconsin have seen amounts greater than 1 inch above normal, with some areas seeing in excess of 4 inches above normal.


48-hour Observed Rainfall, 12/13 -12/14	December Precipitation Departure from Normal

Prior to December 13th, most rivers in the area were still running at high levels from the previous events, and with the rain that fell the 13th and 14th almost entirely becoming direct runoff due to the saturated soils, many areas saw the rivers rise significantly.

How do these flows compare to historical levels?

Data from the US Geological Survey shows comparisons of the current situation to historical conditions. When comparing the current streamflows with what has occurred historically in December, the entire local area is observing streamflows near or above record levels. Simply, this means since records have been kept, most area rivers have not observed flows this high in December.

Maps of Daily Streamflow Compared to Historical Streamflow for December 16-18, 2015

Iowa

Illinois

Missouri

Upper Mississippi River Region

Images courtesy of www.watermonitor.gov / www.waterwatch.usgs.gov

Details of the most current crest flows compared to historical values for some specific river forecast points can be found in the table below. Locations highlighted in cyan are those that have exceeded historical flows for the month of December. The data is preliminary and is provided from the US Geological Survey.

**Historical versus Current December Peak Streamflows**
Location	Period of Record	Historical Dec Peak Streamflow	2015 Dec Peak Streamflow	Crest Date	Associated Gage Height
Wapsipinicon River at Independence	1933-2015	3,780 cfs	11,500 cfs	12/15/15	12.32 ft
Wapsipinicon River at Anamosa	2002-2015	3,240 cfs	11,800 cfs	12/17/15	16.6 ft
Wapsipinicon River at Dewitt	1934-2015	11,100 cfs	*17,200 cfs*	12/22/15	12.97 ft
Maquoketa River at Manchester	2000-2015	1,320 cfs	4,300 cfs	12/15/15	12.8 ft
Maquoketa River at Maquoketa	1913-2015	17,000 cfs	9,430 cfs	12/15/15	21.22 ft
Skunk River at Sigourney	1945-2015	3,600 cfs	9,070 cfs	12/16/15	21.1 ft
Skunk River at Augusta	1914-2015	21,400 cfs	23,700 cfs	12/23/15	15.83 ft
Cedar River at Vinton	2009-2015	7,290 cfs	28,400 cfs	12/17/15	13.51 ft
Cedar River at Cedar Rapids	1902-2015	17,600 cfs	*33,000 cfs*	12/18/15	11.78 ft
Cedar River at Conesville	1939-2015	18,700 cfs	*32,900 cfs*	12/21/15	14.63 ft
Iowa River at Marengo	1956-2015	6,730 cfs	*18,300 cfs*	12/18/15	18.18 ft
Iowa River at Iowa City	1958-2015	6,820 cfs	*11,100 cfs*	12/21/15	19.96 ft
Iowa River at Lone Tree	1958-2015	13,000 cfs	18,000 cfs	12/16/15	16.38 ft
Iowa River at Wapello	1958-2015	29,300 cfs	*42,100 cfs*	12/22/15	22.30 ft
Iowa River at Oakville	2009-2015	27,100 cfs	*43,000 cfs*	12/23/15	11.61 ft
English River at Kalona	1939-2015	4,960 cfs	11,100 cfs	12/15/15	18.75 ft
Des Moines River at Keosauqua	1969-2015	30,400 cfs	55,000 cfs	12/14/15	22.81 ft
Fox River at Wayland	1922-2014	9,420 cfs	6,240 cfs	12/14/15	14.45 ft

With the high streamflows, flooding is occurring in many areas, please see the NWS Advanced Hydrologic Prediction Service for details of latest observations and forecasts for a river in your area.

Additional information is available from the US Geological Survey at waterwatch.usgs.gov.

Current Streamflow	Drought

Flood	Past Flow/Runoff

High River Levels in Winter

Historical versus Current December Peak Streamflows