Record December Rainfall and River Flows Are Sending a Message

Published on: by Gary Siegwarth Category:Editorial
The record December flow levels on the Turkey River last week is an indicator of both changing extreme weather patterns and continued alterations of land use in the watershed. Since the record flood of 2008, ongoing land alterations such as tiling, land clearing, loss of grasslands, and conversion of more land to row crop production throughout the watershed speeds up the delivery of water to downstream locations. The cumulative effect of these changes will increase the likelihood of severe flooding when heavy rain patterns return.
The record December flow levels on the Turkey River last week is an indicator of both changing extreme weather patterns and continued alterations of land use in the watershed. Since the record flood of 2008, ongoing land alterations such as tiling, land clearing, loss of grasslands, and conversion of more land to row crop production throughout the watershed speeds up the delivery of water to downstream locations. The cumulative effect of these changes will increase the likelihood of severe flooding when heavy rain patterns return.

The ultimate barometer of the land and climate is once again trying to tell us something. That barometer for Clayton County is the Turkey River and it’s worth our time to look closely at what the river is telling us. History tells us that rivers and streams in the Midwest don’t flood in December. The Turkey River is usually low and crystal clear this time of year. Fish have migrated to their traditional overwintering areas where they were expecting to hold out in clear, slack water pools until the spring melt. Precipitation records also tell us it never rains this much in December. According to Iowa state climatologist Harry Hillaker, the last storm system that dumped several inches of rain across much of Iowa is four to five times what the state normally sees in the entire month of December. Moderate rainfall totals that fell in the Turkey River watershed during the last rainfall doesn’t usually result in such a rapid rise in river levels. The brown color of the river is an indicator that unusually large amounts of soil and nutrients made their way off unprotected farm fields that are usually frozen this time of year. So what is going on?

Natural features such as wetlands (top left) and other native vegetation historically functioned to capture, filter, and slow the flow of water following heavy rainfall. Continued land alterations reduce the water holding capacity, sending water downstream at an accelerated rate. Most of these widespread alterations, such as tiling and clearing, are irreversible in the short term. The unusually warm December and recent heavy rainfall should also be a concern to area farmers, making fall tilled fields and fall nitrogen application extremely susceptible to significant soil and nutrient losses downstream. With lower corn prices, these losses become ever more important from a profit/loss perspective.
Natural features such as wetlands (top left) and other native vegetation historically functioned to capture, filter, and slow the flow of water following heavy rainfall. Continued land alterations reduce the water holding capacity, sending water downstream at an accelerated rate. Most of these widespread alterations, such as tiling and clearing, are irreversible in the short term. The unusually warm December and recent heavy rainfall should also be a concern to area farmers, making fall tilled fields and fall nitrogen application extremely susceptible to significant soil and nutrient losses downstream. With lower corn prices, these losses become ever more important from a profit/loss perspective.

Let’s start where the river begins, with the rain. Rainfall is influenced by weather patterns and the overall climate, which historical records clearly show is getting warmer on a global scale. According to the Land-Ocean Temperature Index published by NASA, the average global temperature for both October and November were more than one degree warmer than any previous year since record keeping began in 1880. December is on pace for record shattering temperatures as well. The agency also conducted a five-year analysis and found the period from 2011 to 2015 to be the hottest five-year period ever recorded. The World Meteorological Organization attributes this to both human-induced warming and the El Nino climate pattern, which is ongoing. What this means for us is unpredictable weather patterns and extreme precipitation events, which most of us can’t do much about in the short term. What we can do something about is what happens on the land after the rain falls. That’s our responsibility.
Following the record flooding of 2008, Clayton County was instrumental in helping form the Turkey River Watershed Management Authority. The authority is a voluntary, cooperative effort among twenty three cities, five counties, and seven soil and water conservation districts within the Turkey River Watershed. The goal is to reduce flood risks, improve water quality, educate residents, and to develop a plan and secure funding for flood reduction projects. Although the authority has made significant progress with various projects in the watershed, the overriding consequences of ongoing land alterations (draining, ditching, tiling, and conversion of wildlife habitat to row crops) and the slow adoption of conservation practices like no-till have set the stage for drastically higher flood levels in the near future. This means if the exact same precipitation totals that caused record flooding in 2008 fell in the watershed today, that water would be delivered downstream even faster and cause record shattering flood levels in downstream communities. The moderate rainfall totals experienced last week were enough to cause the Turkey River at Garber to rise nearly thirteen feet in less than 24 hours.
Although a growing number of producers have adopted no-till, cover crops, and other conservation practices proven to significantly slow down water movement and soil loss, the overall number using those practices within the watershed is not enough to offset those not participating. With almost every river in the state swelling to near-record levels for this time of year, farmers are getting an unusually timed lesson on the dangers of exposed soils.

“It’s the kind of rain that should open some eyes and make some people think maybe they shouldn’t be doing so much fall tillage,” said Iowa State field agronomist Mark Johnson. Fields will see varying levels of damage, depending on the farming practice, Johnson said.
Recently tilled fields will be most at risk for soil erosion and nutrient loss. Any fall nitrogen applications that went on when soils were still warm and converted to nitrates will also be at risk of leaching, he added.
These nitrates eventually make their way to the river. The greatest loss from heavy rains is more permanent, however. “The biggest loss is topsoil, and unfortunately a lot of farmers probably don’t realize how much they’re losing,” Johnson said. “And that’s not replaceable in their lifetime.” Even with the known soil health benefits, better water infiltration rates, drastic soil erosion reduction, and nitrogen holding capacity of no-till and cover crops, it has been surprisingly difficult to get producers to adopt these practices. Practices that also reduce flooding and keep soil out of the river.

The integration of small wetlands and ponds across the landscape work to significantly slow down water, soil, and nutrient movement off the land during heavy rainfall. They also provide valuable wildlife habitat at the same time. There are numerous cost share opportunities for a variety of conservation practices that are available to landowners through the NRCS office (563-245-1048).
The integration of small wetlands and ponds across the landscape work to significantly slow down water, soil, and nutrient movement off the land during heavy rainfall. They also provide valuable wildlife habitat at the same time. There are numerous cost share opportunities for a variety of conservation practices that are available to landowners through the NRCS office (563-245-1048).

The overall picture of what the Turkey River barometer is telling us from the most recent record setting December rainfall might not seem so merry during this Christmas season. In the era of increasingly variable and unpredictable weather patterns, the key question is how to get a majority of producers to adopt proven conservation practices that improve overall profitability, save irreplaceable soil, keep expensive fertilizer on the fields, while reducing the threat of flooding at the same time. These things are no doubt on the Christmas wish list for the future of a healthy and more stable river barometer.