Stabilizing the Rincon Watershed: The Need for Rehabilitation Part 1 – Downstream

Posted by Karen Ray on October 2, 2020 9:41 PM

Sand – it’s everywhere! Erosion, blocked outflows, increased flood risk, clogged canals and other symptoms of the unhealthy Rincon Arroyo Watershed are screaming for attention and rehabilitation. In fact, locals call the Rincon Arroyo “Sandy Draw” and it’s presented problems for years.

Members of the South Central New Mexico Stormwater Management Coalition (SCNMSMC, AKA Stormwater Coalition), local farmers and several federal agencies have heard the cry and aim to do something about it. Following years of new vision for addressing the issues plaguing this watershed this diverse coalition spent a long day touring the Rincon Arroyo Watershed in January of this year. The diverse topography includes tufted tobosa grass plains, eroding banks flanking the deep sands of large arroyo systems, and vistas overlooking decades-old flood control measures put in place to conserve rangeland. Some of the oldest flood control measures were clearly designed to keep sediment on the watershed and out of the Rio Grande riverbed but most have failed. According to a study commissioned by International Boundary Water Commission (IBWC) an estimated 36.2 acre-feet per year (AFY) of sediment is deposited into the Rio Grande from this system.

The tour was organized by Connie Maxwell, graduate research assistant with the New Mexico Water Resources Research Institute (NM WRRI) and co-chair of the Stormwater Coalition’s Watershed Restoration Working Group, John Gwynne, Dona Ana County Flood Commission Director and Chairman of the Stormwater Coalition, Zack Libbin, District Engineer with Elephant Butte Irrigation District who also serves as the co-chair of the Stormwater Coalition, and the leaders of the Bureau of Land Management’s (BLM) local Resource Advisory Council (RAC). Tour attendees and watershed stakeholders were given a thorough overview of the watershed condition and issues contributing to the excessive erosion.

Don McClure, BLM Assistant District Manager, Jack Barnitz, BLM Supervisory Natural Resources Specialist, and Ayana Brown of the Natural Resources Conservation Service (NRCS), along with other tour members began by viewing the downstream sites on the Rincon Arroyo. They observed acute silting and erosion problems resulting from the poor condition of the Rincon watershed.

Overlooking a very wide portion of the Rincon Arroyo during the late winter tour, Gwynne explained, “We have a real big problem with the amount of sediment that’s here. The vertical bank of the arroyo is ready to drop off into a farmer’s field…between now and monsoon season we’re going to have to get out here and do some work to try and save that section of the arroyo.” Further up the arroyo he said, “There’s another vertical face on this side, same thing, it’s about to go through. But if it goes through on this side, we have homes and the Rincon Wastewater Treatment Plant right here. We have to address these things between now and monsoon season with literally temporary fixes. We don’t have nearly enough dollars to try to fix this at this time. Still, we’ll probably expend, between dollars and manpower about $100,000 just bandaiding it to just to keep it going.”

Hatch Valley farmer Bill Porter, whose fields and orchards flank Sandy Draw on both sides, has routinely cleaned a section of the arroyo channel running through his land to remove sediment and keep it within reasonable bounds. During the tour he said, “This thing could break either direction, not to mention some of the homes and things that would be affected here on this side.” He added that on one side of the arroyo alone, 160 acres of high quality productive agricultural land would be affected. The Rincon Arroyo presents extreme challenges to Porter and other farmers and requires ongoing maintenance.

This summer, EBID crews, led by EBID’s North area Maintenance Foreman, Casey McGuire, completed emergency maintenance on this section of the Rincon Arroyo. McGuire also serves as supervisor of the Caballo Soil and Water District. In addition, railroad crews conducted work to address the problem around the railroad. Libbin says, “Great work was done. It saved significant farmland that no-doubt would have been wiped out by the next storm.” However, they stress that this is just a temporary emergency bandaid. Further maintenance and stabilization work are planned for this troublesome area.

Longtime EBID Manager-Treasurer, Gary Esslinger commented, “I’ve seen this arroyo run as high as 4500 cubic feet per second (cfs)…it can also be as low as 2500 cfs. These monsoon storm events happen when we’re trying to irrigate farmers in this valley. So if the river is already carrying maybe 2500 cfs, then, when you add another 2500 to it you’re getting close to flooding someplace else on this river all the way down into El Paso.”

The next stop was the county maintained Kit Carson Road and associated bridge crossing a narrow section of the Rincon Arroyo 0.25 mile above where it empties into the Rio Grande channel. Upstream of this bridge the arroyo narrows into a bottleneck to accommodate the limited width of the bridge and EBID has installed a ramp flume flow-meter just downstream of the bridge as part of its stormwater capture and monitoring program. This allows them to understand and measure how much water is being discharged into the river here and what to expect downstream.

Gwynne described the critical problems at this site. “One of the other main issues is all the sediment coming in and flowing down towards the river; when it flows hard it can actually block off the outlet to the river itself. The International Boundary and Water Commission (IBWC) has been out here cleaning that section right around the river to try to keep that open on a regular basis. It’s an ongoing task.”

Blocked outlets are a serious problem for EBID’s drain system as well. “In order to keep the groundwater table at a reasonable elevation for the farms, the drains need to continue to flow,” Libbin explained, “When we get four to five feet of sediment in the river, that drain can no longer flow and we’ve experienced that here. This drain runs a long way, ending up down by Tonuco Mountain and draining back into the river.” IBWC has completed significant sediment removal over the last couple of years, he said. Prior to that, when EBID cleaned out the drain, a five-foot wall of sediment remained at the end, blocking the outlet. He said, “The river had just aggraded so much getting down through those narrows that our drain wouldn’t flow. That impacts the productivity of the farmland just upstream.”

IBWC has considerably increased their river channel maintenance. However, Libbin said, “The fact that over the last 15 years or so not much maintenance had been done leaves us with an aggraded channel. This has definitely decreased the capacity of that river channel and the levees, perhaps threatening the effort that was put into raising them and their certifiability.” The IBWC currently has consultants studying how much the flow capacity of the river has been decreased by sediment accumulation.

With the NM WRRI, Maxwell has been studying how the condition of the Rincon Arroyo and other arid watersheds effect the energy of the flood flows to seek potential watershed restoration strategies. In a 2019 research article, Maxwell and other researchers explain, “Throughout the increasingly arid Hatch and Mesilla Valleys, as is common across the Southwest, vegetation loss in upland watersheds is leading to floods that scour soils and transport sediment.” This results in downstream silting in of riparian areas and agricultural infrastructure like flood control dams, canals and ditches as well as the Rio Grande channel itself.  She notes that “higher flow energies and decreased infiltration are diminishing water storage across the landscape, negatively impacting agriculture and ecosystems”. She and others at the Stormwater Coalition emphasize how critical it is to address the basic causes of these high energy flows rather than simply continue the many years of emergency bandaid solutions.

Maxwell and Richard Davidson are also co-founders of the non-profit organization, the Alamosa Land Institute, and have researched potential solutions and sites for several proposed watershed restoration methods. Several of these will be discussed in part two of this series. One goal is to reduce the quantity of sediment reaching the river and contributing further to the ongoing maintenance issues. Keeping the river channel and irrigation system clear and functioning in their roles of water delivery and flood control is a primary goal.

Esslinger and Gwynne both emphasized the public safety concerns facing the region if nothing is done to rehabilitate the watershed and address these issues. “Clearly, when you get flows of 10,000 CFS or more, somebody is going to get hurt. I don’t think the levees can hold that amount of water,” Esslinger said, “2006 was a good example; it came off the Placitas and around the Uvas Mountains and flooded out Hatch with three feet of water.”

“One of the other things that happens from a flood control standpoint,” said Gwynne, “is that we have drainage systems throughout our communities. They are all affected by the interrelated systems. What happens when these arroyos are plugged up and the water can’t get out?”

Echoing these concerns, Esslinger said, “This is a wake-up call. All of us here have an obligation and a duty to try to fix these watersheds and improve them so that we can slow the water down and manage it to the point that we can settle the silt out before it gets in the river and then utilize the water to recharge our aquifers.” Conservation practices in watersheds such as the Rincon have great potential to improve these conditions. A well-planned and implemented watershed project plan can also “address a myriad of natural resource issues such as water quality, soil erosion, animal waste management, irrigation, water management, municipal water and recreation,” according to the Coalition.

Collaborating agencies emphasize the need to address the Rincon Arroyo’s problems with more than just emergency measures. It is critical to head upstream into the watershed itself. Part two of this series will explore the findings of the tour and discuss proposed measures to repair the Rincon Watershed.

(EBID Staff Report)

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