Farm Progress

Calculating water consumption and use on the farm makes it easier to measure and implement changes to achieve a "water balance."

Tyler Harris, Editor

November 30, 2016

4 Min Read

This article is the first in a series on water consumption and use from the perspectives of supply and watershed management. This series will be produced in connection with the Nebraska Water Balance Alliance (NEWBA) and several of its associates.

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Water is the fundamental driver of not only agriculture, but also life in general. When there isn't enough of it, crops fail. When there's too much, soils get saturated, and fields experience runoff, loss of nitrogen and increased disease pressure. The issue of access to water and who has the right to use it affects everyone from agricultural producers to industry to municipalities to environmental stakeholders. It's no surprise that when NASA explores the universe in search of extraterrestrial life, they start by searching for water.

However, the question of how to address water supply is difficult to answer. Ted Tietjen, project coordinator for the Nebraska Water Balance Alliance, is a proponent of a watershed-wide approach to managing and measuring water — both in and out — to calculate the overall "water balance."

It starts with precipitation
Measuring how much water is available starts with precipitation. "This is a critical component if you're talking about use and consumption, because the amount of water that's available is going to affect your decision-making," Tietjen says. "If the Republican River Basin had 30 inches of rainfall during the growing season, the discussion would be completely different in that part of the world."

The water that comes from precipitation is used and consumed in different ways:
• Water use refers to managing the water in a way that it remains available and can be retrieved and reused in the area. When surface water is diverted for certain uses, but not completely consumed, the remaining water can return to the stream or recharge the aquifer, and be available to meet additional needs.
• When water is consumed, it's no longer available for other needs. Examples of water consumption include when water is lost to evaporation, when it's transpired by vegetation, when it is transported out of the area, or when the water quality is impaired to the extent it can't be reused.

Frank Kwapnioski, president at H2Options Engineering LLC of Lincoln and a NEWBA adviser, notes when it comes to water consumption, evapotranspiration (ET) is the primary driver. "Precipitation, which falls directly in the area or falls in another place and flows into the area, is the water supply," Kwapnioski says. "But if you don't first understand the amount of precipitation available and how much of it is consumed, you really don't know how much, if any, additional water you can consume and still remain in balance."

Striking a ‘water balance’
So, if it takes 19 inches of water to grow a corn plant to full maturity, but the field receives 13 inches of rainfall during the growing season, it would take at least 6 inches of supplemental water, depending on the overall water efficiency, to meet that crop's needs.

This additional 6 inches can be and is often met through different management practices. While the amount of rainfall received during the growing season doesn't always equate to the amount required by the crop, that doesn't mean the water that falls the rest of the year isn't available to the producer to help grow the crop.

For example, moisture can be borrowed from the soil to meet the needs of the crop, and practices like no-till and leaving residue on the surface improve the soil's water-holding capacity and reduce evaporation.

In addition, irrigation can be used to help meet the needs of the crop — either from groundwater storage, or diverted surface water and storage produced by off-season precipitation. However, it's important to note that as long as irrigators consume no more than the total amount of water they receive annually, on average, as rainfall or diverted surface water, they can still fall within the "water balance."

Sustainability is a term that, while used in every segment of agriculture, has different meanings to different stakeholders. However, in its simplest form, when water needs can be met in a way that consumes no more water than the amount that is annual, on average, renewed across the watershed, water sustainability can be achieved, by striking a "water balance."

This kind of "checkbook math" approach makes it easier to measure the change in water supply across a watershed and to implement changes to conserve water supply at the farm level, notes Roric Paulman, NEWBA member, who farms near Sutherland.

"I have years where I receive 18 to 20 inches of rainfall, but during the growing season I may only get 6 inches. I may have to pump 6 to 12 acre-inches and borrow 6 more inches from the ground to make up the rest, depending on the crop grown and my total water efficiency." Paulman says. "I think that's the best way a grower or individual at the farm level can understand it."

In upcoming articles, read about management strategies for measuring and managing water consumption and use, and what the overall water supply and consumption approach can mean for different stakeholders.

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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