Farm Progress

Understanding where and how much water is consumed helps minimize the amount lost to nonproductive evaporation and transpiration.

Tyler Harris, Editor

December 28, 2016

5 Min Read
UNDERSTANDING CONSUMPTION: Frank Kwapnioski says to get a handle on water consumption, it must be managed at the whole level across the state. In Nebraska, supplemental irrigation only accounts for 5% to 10% of the state's total water consumption.Tyler Harris

This article is the second in a series of articles discussing water consumption and use from a supply perspective as it relates to watershed management concepts. This series will be produced in connection with the Nebraska Water Balance Alliance (NEWBA) and several of its associates.

When it comes to water, a particular passage from “The Rime of the Ancient Mariner” always comes to mind: "Water, water everywhere, and not a drop to drink." It's the fundamental driver for environmental, industrial, municipal and, of course, agricultural interests. It's the subject of headlines and coffee shop talk when there isn't enough of it, when there's too much, and when quality is impaired to the extent it's no longer usable.

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FIGURE 1: About 80 million acre-feet, or 80% to 90% of the water used in Nebraska, is consumed at the land surface. This includes transpiration by native vegetation, lawns and crops, both rain-fed and irrigated, and evaporation from water surfaces, soils, wetlands and infrastructure.

With the number of interests that rely on water, how do you talk about water consumption and use in an objective manner? Frank Kwapnioski, of H2Options Engineering LLC of Lincoln and a NEWBA adviser, says having a relative understanding of the different components of a water supply-and-demand budget can help stakeholders make sound management decisions based on quantified data.

"If we plan to protect the resource, we must value it properly," Kwapnioski says. "Because of a lack of ability to quantify consumption, in the past water management has been based on more qualitative understandings and concerns for streamflow. New and emerging technologies now offer a chance to better quantify both supply and demand to a degree not possible in the past. These technologies can support comprehensive and systematic assessments at frames of reference that were really not practical before. These technologies are not, in themselves, 'a silver bullet,' but together they can help inform decisions at all water management scales."

Where does it all go?
So, who are the big players in water consumption? Take Nebraska for example. Rainfall varies from one part of the state to another, but depending on the year, Nebraska on average receives 80 million to 100 million acre-feet of precipitation annually, according to a chapter written by former University of Nebraska-Lincoln Conservation and Survey Division director Vincent Dreeszen in the 1993 book, "Flat Water: A History of Nebraska and its Water." On average, that's 90 million acre-feet the state starts off with.

Nebraska is made up of about 49 million acres, and according to Dreeszen, the majority (about 80 million acre-feet, or 80% to 90%) of the water consumed in Nebraska is consumed at the land surface — that is, it's lost to evapotranspiration (ET). That includes transpiration by native vegetation, lawns and crops, both rain-fed and irrigated, and evaporation from water surfaces, soils, wetlands and infrastructure (see Figure 1). As mentioned in the previous article, when water is consumed, it's no longer available for any other consumption or use.

All land surfaces evaporate or transpire at some rate. Based on ET maps produced by Jozsef Szilagyi, research hydrologist at UNL's School of Natural Resources, evapotranspiration varies significantly based on location and land use.

For example, urban areas in eastern Nebraska like Omaha and Lincoln have ET levels more like the Panhandle than their immediate surrounding area. Szilgayi's maps indicate that with all their highways, storm drains, rooftops and other concrete infrastructure, urban areas get rid of water by running it to streams before it can be lost to ET. On the other hand, open bodies of water, like lakes and reservoirs, generally evaporate water at a much-accelerated rate compared to their surrounding land area. However, heavy forested areas in riparian alluvial region, because of water availability, can transpire water at nearly the same or greater rates than nearby bodies of water evaporate.

According to Dreeszen's statistics, about 7% of Nebraska's total 49 million acres are dedicated to urban and highway infrastructure, state and federal institutions, parks, wildlife and other uses. Nebraska, while considered the Arbor Day state, is made up of only a small percent of forested area, about 2%. Of the remaining 91%, 43% is grazing land (we may be the Cornhusker State, but we love our rangeland) and 48% of the total land area is cropland and ranches. Meanwhile, about 16% to 17% of that 48% is irrigated.

Dreeszen's numbers indicate that while about 80% to 90% of the water consumed in the state is consumed at the land surface, supplemental irrigation only accounts for roughly 5% to 10% of the remaining 10% to 20%. Roughly zero to 5% is used for aquifer recharge; 1% is consumed in municipalities; 1% by industry; 1% by livestock; and 1% by domestic consumption, according to 1993 statistics. About 9 million acre-feet, or 10% of the total annual water supply, leaves the state as streamflow.

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FIGURE 2: Estimated annual evapotranspiration (ET) rates in inches in Nebraska in 2000-09. Urban areas like Omaha and Lincoln have ET levels more like the Nebraska Panhandle than their immediate surrounding area. This map indicates that with all their highways, storm drains, rooftops and other concrete infrastructure, urban areas get rid of water, by running off to streams, before it can be lost to ET. (Map courtesy of Jozsef Szilagyi)

What can be done?
Using this information, Ted Tietjen, NEWBA project coordinator, notes landowners could identify nonproductive consumption to manage it accordingly. Whether water is transpired by undesirable invasive vegetation, or evaporated from soil that has no cover.

"Removing undesirable vegetation or managing farm ground so there always is cover will reduce transpiration and evaporation, and decrease consumptive water use. An example would be in summer fallow practices: Tilling the soil leaving the soil bare, normally has a 60- to 80-degree higher surface temperature than a summer fallowed field that has good residue cover reflecting the sunlight and reducing evaporation.  For every inch of water you save, that's worth 8 bushels of wheat. Wheat isn't worth as much as it was a couple years ago, but that's still an impact on the bottom line," Tietjen says. "I think we can probably concentrate on how we can reduce nonproductive consumption through transpiration or evaporation."

In upcoming articles in Nebraska Farmer, read about strategies for measuring and managing water consumption and use. To learn more, contact Kwapnioski at [email protected], or Tietjen at [email protected].

 

 

About the Author(s)

Tyler Harris

Editor, Wallaces Farmer

Tyler Harris is the editor for Wallaces Farmer. He started at Farm Progress as a field editor, covering Missouri, Kansas and Iowa. Before joining Farm Progress, Tyler got his feet wet covering agriculture and rural issues while attending the University of Iowa, taking any chance he could to get outside the city limits and get on to the farm. This included working for Kalona News, south of Iowa City in the town of Kalona, followed by an internship at Wallaces Farmer in Des Moines after graduation.

Coming from a farm family in southwest Iowa, Tyler is largely interested in how issues impact people at the producer level. True to the reason he started reporting, he loves getting out of town and meeting with producers on the farm, which also gives him a firsthand look at how agriculture and urban interact.

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