What About 2015?

Rain Garden in UT Gardens, Knoxville

The Rain Garden at the UT Gardens in Knoxville is an active demonstration of how to manage runoff naturally. Photo courtesy UTIA.


 

As 2014 comes to a close, the year was “normal” for Tennessee in terms of overall rainfall. Annual accumulations are averaging around 50 inches around the state. That’s a far cry from the averages for 2013 – which was the wettest year in recent memory.

Andrea Ludwig, a watershed management specialist with University of Tennessee Extension, says the data backs up our memories of a soggy 2013 versus 2014. “Looking back on 2013, we have good reason to think of it as the wettest year we can remember, because it was the wettest in 30 years,” she said.

Records indicated that in Knoxville, Tenn., average annual rainfall is 48 inches.  It is 54 inches, 52 inches, and 47 inches for Memphis, Nashville, and Chattanooga, respectively. Up to 62 inches of precipitation falls along the southern portion of the Cumberland Plateau. But as we commonly see in climate patterns across the Southeast, actual observations from year to year can deviate substantially from the long-term averages.

Total annual rainfall in 2013 in Knoxville was approximately 67 inches -- 19 inches or approximately 37 percent more than the area’s average annual rainfall. Records indicate 2013 was also wetter than average across the state, where Nashville saw 56 inches of rainfall and Memphis experienced 64 inches of rainfall, both well above their annual averages. 

The wettest year on record for Knoxville according to data from the National Oceanic and Atmospheric Administration (NOAA) was the year 1875. Rainfall that year totaled 73.7 inches, or 54 percent greater than the current annual average.

“2013 felt like such a wet year as compared to 2014 because we had a relatively high number of days of recorded rainfall,” said Ludwig. “In Knoxville in 2013, we experienced 90 days with rainfall accumulation of over 0.1 inches daily. The average for this area in the previous 30 years is 83 days.” Records indicate there were 85 days of recorded rainfall in the Nashville area, while only 72 days in the Memphis area.

“Much of this impression can be attributed to that very wet month of January 2013, where it rained more than 12 inches in many parts of the state. A typical monthly accumulation for January is between 3-5 inches, such as we saw in 2014,” she said.

“So we’ll have to see what kind of precipitation January holds for us and make predictions about 2015.”

Daily rainfall accumulation is measured at weather stations across the state and made available online by NOAA.

Looking ahead to 2015, Ludwig says meteorologists can make educated guesses as to what pattern will emerge, but they are predictions. “The Old Farmer’s Almanac reports that Tennessee will see a cold and dry winter with little significant snowfall leading into a warmer-than-normal spring with above normal rainfall,” she said. “National records show that the occurrence of abnormally high annual precipitation totals has increased since 1990 in most regions, while roughly 20-70 percent of the country experienced drought sometime between 2000 and 2013. So we’ll just have to see what 2015 has in store for us.”

Ludwig reminds us all why we care about rainfall. “Rainfall patterns affect many aspects of day-to-day life, including food crop production, keeping the lawn green, and local flooding.  The 2013 wet year meant that there was a large amount of water running off of our rooftops and pavements,” she said.

“A typical residential home sheds over 100 cubic feet of water from its rooftop with just 1 inch of rainfall. This runoff often drains directly into the nearest creek instead of soaking into the soil, as it did before we built on top of it.  This means that it causes damage and flooding downstream very quickly, rather than infiltrating into the soil and slowly finding its way to the stream over a much longer period,” Ludwig said.

Ludwig and other scientists and engineers at the UT Stormwater Management Assistance, Research, and Training (SMART) Center are helping develop ways to minimize the negative impacts of stormwater.  This includes developing new practices, new tools for design, and new information and training materials.


To find out about ways to make your lawn and garden areas absorb more rainfall, check out the Tennessee Smart Yards page for details on lawn care and using rain gardens (www.tnyards.utk.edu).  You can also visit the UT Gardens Rain Garden to see how a rain garden soaks in runoff.  We estimate that in 2013 the UT Gardens Rain Garden soaked in over 5,700 cubic feet of runoff.  That is enough to fill two-thirds of an Olympic-sized pool!

UT Extension provides a gateway to the University of Tennessee as the outreach unit of the UT Institute of Agriculture. With an office in every Tennessee county, UT Extension delivers educational programs and research-based information to citizens throughout the state. In cooperation with Tennessee State University, UT Extension works with farmers, families, youth and communities to improve lives by addressing problems and issues at the local, state and national levels.


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Contact:

Andrea Ludwig, Department of Biosystems Engineering and Soil Science, 865-974-7238, aludwig@utk.edu

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