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First in a series
Long term, a changing climate in the already arid Southwest likely will send less mountain snowmelt and monsoon rain down the Rio Grande to Corrales. Warnings already have been issued about a drying riverbed along this stretch of the Middle Rio Grande Valley with obvious implications for fish and vegetation here. Less obvious are implications for the wells from which Corraleños draw water for their homes. Water authorities are working on a plan for the next 50 years that is scheduled for release next year. Will changing conditions require re-negotiation of the 1938 interstate treaty, the Rio Grande Compact, that requires New Mexico to send river water to Texas?
For millennia, flows in the Rio  Grande have recharged aquifers, including those from which your home’s water is drawn. When that recharge is diminished, the upper water table is expected to drop. What is the effect, over time, on deeper aquifers? Infrequently, Corrales Comment checks in with well drillers who serve this area to ask whether water levels below are steady or receding. Usually the answers are reassuring: despite a major increase in pumping at homes and businesses —such as Intel, farmers and brewers— aquifers from which most Corraleños draw are in good shape —for now.
By Scott Manning
To better understand the challenges posed by climate change to water resources in New Mexico, the Interstate Stream Commission is conducting a 50-Year Plan that assesses the impacts of climate change. It aims at determining the resiliency of New Mexico communities to these changes, and proposes adaptation strategies, where needed.
Development of the 50-Year Water Plan will occur in four phases. Phase 1 of the plan began in January 2021 and ended by March 1. This phase involved assessing the process itself with the New Mexico Water Dialogue, coordinating experts with the New Mexico Bureau of Geology and Mineral Resources (NMBGMR), and building consensus on approaches to the plan.
Phase 2, referred to as “The Leap Ahead Analysis,†began on March 1 and ended on June 30. The purpose of the analysis was for experts, led by the bureau, to compile scientific information about the impact of climate change on New Mexico communities and water supplies. The plan is currently in Phase 3, the outreach and assessment phase, where the Interstate Stream Commission intends to host meetings with citizens of New Mexico to explain the findings of the “Leap Ahead Analysis,†and to interview citizens to determine the degree of resilience New Mexico communities have to the challenges posed by climate change. Other partners in the effort, the US Army Corps of Engineers, the New Mexico Water Resources Research Institute, and the State Indian Affairs Department, will all play a role. This phase will continue through January 2022.
During Phase 4 of the plan, scheduled for spring 2022, the ISC and collaborating authorities will produce, review and finalize a 50-Year Water Plan that will contain guidelines for preparing for climate change, adopting efficient water usage strategies, and improving water resiliency throughout the state. The Bureau of Geology and the Interstate Stream Commission shared summary-level scientific results from the “Leap Ahead Analysis†during their first outreach meeting on July 21.
The water shortages in New Mexico are driven by both a multi-decade climate cycle and a warming climate. In the coming half-century, the bureau reported the average temperature in New Mexico is expected to increase by 5-7 degrees Fahrenheit. Even so, average precipitation is expected to stay relatively constant. But the warmer climate will accelerate processes such as evaporation and transpiration that remove water from the ecosystem and environment. Therefore, a hotter climate, even with constant levels f precipitation, will further strain New Mexico’s water supplies. And the hotter climate will impact the environment in other ways as well. A warmer climate will stress vegetation and allow fires to proliferate, thereby reducing plant cover in New Mexico biomes.
This biome damage makes the environment less resilient to erosion and flooding, meaning that storms will cause greater environmental damage. The damage could disrupt normal drainage systems and damage water infrastructure, further straining water resources. Water quality will decrease as well, the study indicates, with the increase of water temperature and potential growth of bacteria in water supplies. This climate change analysis demonstrates the need for the state to continue to assess its vulnerabilities to climate change. The ongoing drought in the state causes short-term water shortages that strain farmers and New Mexico residents. But water concerns are unlikely to go away as New Mexico becomes hotter and dryer in the coming decades.
In the face of a serious drought throughout New Mexico, officials at the Middle Rio Grande Conservancy District (MRGCD), the New Mexico Interstate Stream Commission and the Albuquerque-Bernalillo County Water Utility Authority (ABCWUA) are taking steps to conserve water and to conduct studies about the impact of climate change on the future water supply in the state. Interstate Stream Commission Director Rolf Schmidt-Petersen explained that New Mexico is currently enduring a second year of water shortage caused by severe drought. In 2020, poor mountain snowpack and reduced runoff water created a severe drought situation. The issue was then compounded by a poor monsoon season last year.
These water shortages have created problems for New Mexico’s water-sharing agreements with neighboring states. One such agreement, the Rio Grande Compact, was signed by New Mexico, Texas and Colorado in 1938; it sets out the water-sharing promises between the three states. The agreement operates through water delivery debits and credits in which states are held responsible for delivering the correct amount of water “payments†to other states. Colorado is expected to deliver water to New Mexico, and New Mexico is expected to discharge water to Elephant Butte reservoir and from there, deliver water to southern New Mexico and Texas. Currently, New Mexico is in compliance with its delivery requirements up to an “accrued debit†of 200,000 acre-feet of water.
The 2020 drought was severe enough to warrant the release of stored Rio Grande Compact debit water from the El Vado Reservoir to supplement Rio Grande flows. New Mexico is required to retain water in storage to the extent of its accrued debit in deliveries to Elephant Butte Reservoir, and it may not store any Rio Grande water when Elephant Butte storage is low. Schmidt-Petersen explained that the water shortages last summer developed rapidly and that without releasing the debit water, the Rio Grande would have dried up at Albuquerque and farmers would have struggled through the rest of the irrigation season.z
Water officials hoped that the depleted water stores and severe drought situation last summer would be resolved over the year with modifications in MRGCD operations, a strong fall rainy period, and better snowpack in 2021. Although the MRGCD made the intended modifications to its operations, the rest of 2020 and the beginning of 2021 continued to be dry, leading to further water supply concerns this summer. That problem was compounded by reduced avalability of water from the San Juan-Chama River system which also has decreased in recent years.
New Mexico began 2020 with a water debit of 40,000 acre-feet, meaning the state was meeting its water-sharing obligations but that 40,000 acre-feet of Rio Grande water would need to be stored upstream before any water could be stored for later release to the middle valley. But the severe drought last summer and subsequent debit water release yielded an increased water debit for 2021 of 96,000 acre-feet. No snowmelt runoff was stored in New Mexico during the 2020-2021 winter because Elephant Butte remained low, New Mexico had a 96,000 acre-foot accrued debit, and the 2021 snowmelt runoff was poor. This meant that New Mexico began summer 2021 in a drought with little water storage. Schmidt-Peterson said New Mexico has not experienced this degree of water deficit since the early 1980s. This makes the recent drought unprecedented in terms of modern New Mexico water policy.