Editor's Note: This is part 6 of a seven-part series on a quarterly public meeting held Monday. October 21, by the Interstate Stream Commission to present ongoing work to evaluate Arizona Water Settlement Act proposals and the planning process. This article addresses questions on the process and a presentation on sub-surface drip irrigation.
"A lot is available on the website," Starr Belsky, Silver City business owner, said. "Please pass on that so many documents are not sorted, it's hard to find things. I recommend preceding the title of all documents with the date. The site is chaotic and not user-friendly."
She said: "It sounds like what's being said is that it's a danger on all sides."
"There is the possibility of some kind of diversion," Belsky continued. "Storing in some fashion could be released for continual river flow. Is that generally the supposition? Is that the tradeoff for the Gila Valley, the potential to keep some flow?"
"Under the CUFA (Consumptive Use and Forbearance Act), whichever New Mexico entity would divert, it could divert only a maximum of 350 cfs, skimming the peaks of high flows," David Anderson, ISC staff, said in reference to a slide shown in his previous presentation.
"Another constraint is the obligations downstream," he explained. "There has to be 30,000 acre-feet of water in the Gila River Indian Community reservoir. At the point of the September flood, there was not that much in the reservoir, but later there was.
"Instream flow is implicit in the Regional Water Supply proposal," Anderson continued. "It would likely be required by the ISC, because it is part of the Gila River Policy.
"If we are going to use water, it will help the users and the ecology," he said. "Water rights for farmers do not include instream flow requirements, but would likely be negotiated."
"My issue with the whole process is more than the particulars of these proposals," Kyle Johnson, Gila resident, said. "I have seen the shameful action by the New Mexico Environment Department in the Copper Rules. The stakeholder process was subverted and it let Freeport get what it wanted. There was no responsibility. The Water Quality Control Board was heavily politicized and it is a partisan board. The process was subverted. 'Thanks for sharing and we did what we wanted to do,' they seemed to say.
"I have no more confidence in Anderson, Roepke nor the ISC itself," he said. "We don't trust you. We come before you and again and again tell you it's a bad idea. I believe a diversion is what you're intending. I will be delighted to find I'm wrong, but I don't think I will be. I think the sentiment is we don't believe it, and we don't trust it.
"Before these people were here, there were two dam proposals that went down because the people weren't willing to pay for the water," Johnson concluded.
"We're here, not to talk about the NMED," Anderson pointed out. "Our state engineer is a fine person. The Interstate Stream commissioners are fine people. The only projects funded so far are the municipal conservation projects.
"We're glad you're here, but you are not representative of the four-county area," he said. "Each proposal is one card in the hand and may have to be part of a decision, not just one thing. We can make up the 30,000 acre-foot water deficit, but it will require help from all four counties."
"I compliment you all," Reese Fullerton, facilitator, said. "You are passionate about what's important, but you're being respectful. It's a wonderful combination.
Next was a presentation by John Conway of a report contributed to by James Bowden, Jeff and Allison Boyd, Lisa Fields, Ron Phair, and himself.
"A couple of meetings ago, I felt uncomfortable about what I was hearing," Conway began. "I want to talk about how extensive conversion to sub-surface drip irrigation in Luna County is contributing to zero depletion status in the Mimbres Basin.
"I want to show why sub-surface drip irrigation does not fit Frank A. Ward's basin model," he continued. "Scientists ask, as drip irrigation is replacing flood, what are the unintended consequences.
"I will show why the model by Ward and Manuel Pulido-Velasquez of the Mesilla Valley is not the same as the Mimbres Basin," Conway said. "I am using the scientific method. I will show how modeling and computers helping direct the outcome as a substitute to direct measurement and experimentation and how the benefit of controlled experiments trumps models.
He said irrigation system efficiency numbers relative to each other would be similar, as they vary by crop and by operator.
Conway noted that closed furrow flooding offers less crop productivity and stresses plants farther away from the source. Pivot sprinklers do a better job of spreading water, but close to the roots is best.
"Drip irrigation has better relative efficiency, but you will lose some to the atmosphere," he said. "The most vast improvement has been sub-surface water-emitting tapes 12 inches down. They offer the best relative efficiency."
Eighty-five percent of irrigated acreage in Luna County is by subsurface drip.
One acre of green chiles with flood irrigation produces 11 tons per acre, for a $3439 gross revenue, and $2457 in operating costs, leaving $982 net operating income, according to the presentation. Whereas, the same one acre of green chiles using sub-surface drip irrigation, yields more than 22 tons, with a $6897 gross revenue, $3840 in operating costs, leaving $3057 net operating income.
"You can use the same amount of water on fewer acres," Conway said. "With subsurface drip you have a $3 to $1 per acre net operating profit. Wells are costly to drill and operate, as pumping consumes 13 percent of the operating budget."
In 1997, the base irrigated acreage was 33,700 acres. In 2009, 2010, 2011, 2012 and 2013, the reported irrigated acreage averaged minus 21 percent from that number.
He said modeled data requires an increase in irrigated acreage to show an increase in basin level depletion rates comparing surface drip with flood irrigation.
"Forget surface drip, just sub-surface drip," Conway said. "It also leads to a reduction in evapotranspiration. It further enhances yields and increases soil oxygenation. Reduced surface wetting provides enhanced yields, and there is more consistent moisture at five feet down than with flood irrigation."
The geology is quite different from the Mesilla Valley model, he stressed. In the Mimbres Basin, irrigation is 100 percent groundwater. The Mesilla Valley model contends drip irrigation depletes the aquifer more than flood irrigation, but water travels faster horizontally in Luna County than in the Mesilla Valley, according to the presentations calculations. The Mimbres Aquifer takes 70 years to recharge from flood irrigation, so no valid conclusions can be drawn regarding flood irrigation recharge of the aquifer.
"Irrigators who make the investment in sub-surface drip irrigation, sometimes with taxpayer help, can look at the 2013 USGS report saying the aquifer is now in balance, after 3.1 million acre-feet of depletion from 1900 to 2008, from the estimated 40 million to 74 million acre-feet of water in the aquifer," Conway pointed out.
He showed various charts and graphs, as well as testimonials from some irrigators.
"The trend line of depletion shows down, down, down through 1999," Conway said of the USGS report used for groundwater trending. "The trend line has slowed down and hopefully is starting to go up.
"On New Mexico 11 south of town, it looks like it's trending up," he said.
"In summary, in the Mimbres Basin, sub-surface drip irrigation uses less water, produces greater yield and generates greater profit than flood irrigation," Conway concluded. "The ISC contention that drip depletes the aquifer is based on poor assumptions and flawed analysis.