Surface irrigation sometimes gets a bad rap, and a representative of a pioneering Australian-based company out to automate gravity fed systems pointed this out at a rare presentation on improving efficiency of various forms of flood irrigation.
“The irrigation industry in general, with the exception of the people in this room, if you tell them you want to maximize efficiency with drip irrigation, they’ll put you on their shoulders and throw money at you,” said Alan Jackson, area manager for Rubicon Water.
“If you tell them you want to maximize efficiency with flood irrigation, they pat you on the head and tell you ‘Enjoy your delusions.’”
Jackson and other speakers at the workshop held at the Kearney Agricultural Center in Parlier, Calif. did their best to point out that improving efficiency of surface irrigation is not a delusion.
He was preceded at the podium by Eduardo Bautisto, research hydraulic engineer with the U.S. Department of Agriculture’s Agricultural Research Service based in Maricopa, Ariz. Jackson pointed out that Bautisto had cited “significant improvements you can make.”
Audience member Dave Goorahoo, associate professor of vegetable crop science at California State University, Fresno, said he was particularly impressed with Bautisto’s point that “you can’t improve what you can’t measure.”
Goorahoo said he also found a good take-home message when Khalid Bali, a University of California Cooperative Extension (UCCE) farm advisor in Imperial County, soon to become an irrigation specialist at the Kearney Center, pointed out that maximizing yields with water deliveries isn’t always the optimal goal.
His contention: “Under-irrigation can lower yield, but it may maximize profits. You may not have to look at maximum yield, but at maximum return.”
Reduced water applications may bring rebates, and high prices for buying water may make it more prudent to risk lower yields while reducing the cost of inputs.
Bautista warned that a system could be well designed but inappropriately operated. It could also be well operated but poorly designed.
He looked at several systems judged on the basis of formulas for arriving at high efficiency and cited a model that can be used for doing that. It’s available free by Googling Win SRFR. The National Resources Conservation Service developed the model and a new version of it will be available this year.
Alternative irrigation designs
Bautista, who spoke on improving the hydraulic performance of surface irrigation systems, said irrigation models are tools that allow growers to examine the potential performance of alternative irrigation designs or operational scenarios while taking into account criteria including the length and width of a field, sloping land, and inflow rate.
Bautista cited the use of surface water and efforts at achieving greater efficiency in Australia, where Rubicon Water is headquartered. With more than a decade and a half of drought in that country, it’s no stranger to the challenges of coping with less water.
Most land in Australia is surface irrigated and there are typically long runs, Bautista said. Growers there must wrestle with high energy and labor costs, and unpredictable surface supplies, which is a disincentive to investing in pressurized irrigation.
Established in 1995, Rubicon has sold more than 20,000 control and measurement devices to irrigation districts and farms in 10 countries.
Its FarmConnect systems allow farmers to remotely manage their gravity irrigation. The company has automated flume gates that optimize delivery of water through canals and eliminate spillage at the end of ditches.
FarmConnect provides alarms, soil moisture monitoring, graphing, mapping, automation, and a help menu. Jackson emphasized that all systems – whether drip or flood – “have their applications and all require management.”
Shrinking Californkia snowpack?
Bali said the importance of irrigation efficiency is underscored by warnings that California’s statewide snowpack is projected to shrink drastically, by about 25 percent by 2050. He added that improving efficiency means reducing losses of nutrients, pesticides, and water; and increasing distribution uniformity.
Surface irrigation is just that. It means that water moves on the surface and is not pressurized. It can take forms that include furrow irrigation, use of contour basins, surge irrigation, and border strip irrigation.
Bali said the use of furrow irrigation is rapidly declining in vegetable crops.
He said the runoff rate for border irrigation is between 5 and 20 percent. For furrow irrigation, it’s 15 to 30 percent. The surface runoff means nutrient and pesticide losses and deep percolation.
Bali said there is usually no runoff with basin irrigation. He said deep percolation is sometimes needed for salinity control, and it can be helpful to recycle runoff water, but that may require the use of energy.
Bali recommends regular inspection of the irrigation system, including looking at pressure levels, the flow rate, the filtration system, and leaks.
Daniele Zaccaria, UCCE agricultural water management specialist, discussed irrigation systems and energy efficiency. He touched on groundwater pumping and the need to make sure the equipment is operating efficiently.
It’s expected that his presentation, which was brimming with formulas for determining efficiency, will be posted, along with those of other speakers, at http://ucanr.org/irrigationsoils.
Zaccaria said common causes of poor pumping performance include wear, clogged impellers, and poor suction conditions.
Applied water uniformity
Dan Munk, UCCE irrigation specialist in Fresno County, opened the workshop with a look at some of the challenges of achieving uniformity of applied water, making sure it is evenly applied from top to bottom in a field.
“If there is not good uniformity it is not going to be efficient,” Munk said.
Surface irrigation issues differ from those encountered with pressurized systems, he said, adding that surface irrigation design and operation is governed in part by soil infiltration. And, variable surface intake rates can complicate management.
Munk pointed out that infiltration rates vary throughout the season, usually being higher at pre-irrigation and then lower in the late season.
Small pores in clay soil hold water; large pores in sandy soils conduct water and air. Crust on the soil surface can inhibit penetration. Tillage and cultivation may be needed, Munk said.
The use of organic matter - including manure, composts, lagoon water, chipped residues, and cover crops – can help improve water penetration and management. He added that chemical treatment of soil and water may also be helpful.
Munk warned that high infiltration rates can often result in lower distribution uniformity. At the same time, fields which have water penetration problems have a high distribution uniformity and irrigation efficiency but may be difficult to manage.
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