Editor's Note: This is part 1 of a two- or three-part series on the Tuesday Gila/San Francisco Water Commission meeting.

The Gila/San Francisco Water Commission members addressed a lengthy agenda at their meeting Tuesday, April 16.

The first item of business was to elect a treasurer, as former treasurer Bill Woodward had taken a full-time job. Luna County Commissioner Javier Diaz nominated Grant County Planner Anthony Gutierrez.

"I am not opposed to being treasurer, but if the Grant Soil and Water Conservation District is the fiscal agent, their representative should be treasurer," Gutierrez said.

Alex Thal is that representative and was elected by acclamation.

The next agenda item addressed a revision of a GSFWC informational brochure, originally developed at the commission's request by Mary Alice Murphy. It was approved to pay her up to $500 to revise the brochure and create a PowerPoint for use at talks to community groups.

A briefing on "Defining ecosystem water needs and assessing impacts of climate change and water diversion on riparian and aquatic species and ecosystems of the upper Gila River in New Mexico" by Martha Cooper of The Nature Conservancy was tabled until next month's meeting, as Cooper was ill and could not attend the meeting.

Hydrologist Deborah Hathaway of S.S. Papadopulos & Associates consulting firm was in attendance at the meeting and offered to present her findings from a Gila River hydrologic study, commissioned by the Interstate Stream Commission.

While Hathaway set up the presentation, ISC Deputy Director Craig Roepke gave an overview of what she would present. "It is intended to be informative from the hydrologic viewpoint. It's how groundwater responds to surface water and vice versa."

Hathaway said it was a water model, a computerized way to understand anything about a project. "We carved out four models, but have only modeled two on the upper Gila, one from the Mogollon Creek confluence and the other below the Cliff-Gila Valley."

"At Reach 1, we took riparian vegetation groups and determined how much water they used," she said. "We are developing the relations between the flows and the ecologic relationships. We took a hypothetical year and chose February as the baseline condition for illustrative runs of the model."

Hathaway described three scenarios—Scenario 1 would take the allowed amounts of water, according to the Consumptive Use and Forbearance Agreement of the Arizona Water Settlements Act, at 13,500 acre-feet. Scenario 2 would envision CUFA diversions and a 30 percent increase in irrigation, with Scenario 3 combining the CUFA and a 30 percent increase in riparian vegetation.

Thal said he did not understand how riparian vegetation would increase. Hathaway said it was strictly hypothetical.

She noted the model "would allow us to look at any month."

In Scenario 1, one area of study had up to 1.9 feet of drop in groundwater, in the hypothetical March, "but that was done from the high water level, with the runoff. By June and July, there was little memory of the earlier changes."

Scenario 2 showed no change in the winter, with summer change dependent on the location of irrigated areas, with a groundwater drop of no more than two feet.  Scenario 3 was similar, with no change in the winter and changes in the summer dependent on the vegetation area.

"Fundamentally, there are three parts," Hathaway said. "Step 1 characterizes the altered hydrograph."

Step 2 articulates the flow-ecology relationship, by identifying the physical changes to the hydrologic environment and characterizing the ecological response to the physical change, as well as where it happens and how much.

Step 3 evaluates the benefits/trade-offs and allows the user to accept, mitigate or reject the findings.

Hathaway clarified that Step 1, by characterizing the altered hydrograph, could be different in any given year. The Nature Conservancy's Indicators of Hydrologic Alterations provides descriptive and comparative statistics, but "I want to stress that IHA does not give answers to questions of ecological impacts," she said. "Rather it points to areas of potential sensitivity."

The graphs she showed represented daily flows from 1937 through 2001, giving the values of 65 years. "There are two sets of data, one without the Consumptive Use and Forbearance Agreement and the other with those allowed diversions. We use a flow of 150 cubic feet a second criterion at ISC's suggestion that no water can be taken if the flow is less than 150 cfs."

She showed a graph of a 7-day maximum flow. "The method does not have any relation to specific ecological impact, but I can say, it's not a big change. With the model we can look at minimum and maximum flows, timing and dates, and low and high flow pulses, as well as peak, duration, frequency and the rise and fall rate of flows."

The Range of Variability Approach offers scores for the change in the number of events falling into the lower, middle and upper percentile ranges.

"Most of the flows, even with CUFA, would fall into the little to no change," Hathaway said. "Figure 48 (in the report, which can be viewed at nmawsa.org) shows that the Gila is not a dry river. If you are diverting 300 cfs from 5,000 cfs, you will see no change. However, if it's 300 cfs from 700 cfs, you will see it more noticeably."

March is the only month with the highest change in monthly flows, likely because CUFA will not usually be done in other months.

"The conclusion is that there is no change to low flows or no flows," Hathaway said. "The changes are subtle, and you should examine the full range of statistics to identify focus areas for ecological evaluation. Looking at large floods, as well as small floods, I see nothing notable. This gives us a place to start.

"We need feedback if there are significant impacts if the groundwater drops a few inches to a foot or two feet," Hathaway said.

Thal said he believes the ecological impacts are incomplete. " We need to integrate the physical ecology with the human ecology, so we are not left out."

Hathaway concurred that physical ecology needs to be modeled on the biological side.

"What we have from the models right now is just demonstration models," she said. "Ecologists want to see what happens if there are three dry years, and what happens in 'this' area or to this riparian area or wetland. The tools are evolving. My concern is if we can integrate enough quickly enough to be helpful."

Gutierrez asked if a short-term model, such as might reflect a catastrophic wildfire could be done.

"We can characterize the hydrograph, but the ISC is working on a similar study," Hathaway said. "Since we built the models, we have two years of additional data that we would like to add."

Billy Webb, representing Catron County and the San Francisco Soil and Water Conservation District asked: "Looking at the past two years, how many instances have we seen where we could have taken the CUFA allocation?"

"I'm thinking it's not so good," Hathaway said.

Chairman Tom Bates said: "That's why it's 140,000 acre-feet over 10 years."

The next article will cover most of the rest of the meeting, with a possible third article required.

Live from Silver City

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