Climate Change in New Mexico Over the Next 50 Years: Impacts on Water Resources

Abstract

All water that we use in New Mexico originates as rain or snow falling onto the landscape, which either goes to groundwater or surface water or returns to the atmosphere. Of the precipitation that falls on the state, 1.6% runs off into streams and rivers, and 1.8% infiltrates into the ground, recharging subsurface aquifers. Much larger proportions are transpired by plants (78.9%) or evaporated (17.7%). The impact of climate change on all of these pathways will affect our state's water budget. Notably, because of the larger percentages of water lost to evaporation or transpiration, even very small changes in these factors will result in large changes to runoff and recharge. As mentioned in Chapter 2, the climate will continue to warm over the next 50 years, likely without an increase in precipitation, leading to greater statewide aridity. Hydrological modeling indicates declines in both runoff and recharge going forward, amounting to 3% to 5% per decade for both quantities. Historical trends in runoff indicate significant year-to-year variability, as do trends in soil moisture and recharge. But all are generally decreasing, consistent with the results of climate models that project a drying climate. Combining the historical trends with modeling of future changes, significant decreases in runoff and recharge seem very likely. TERRESTRIAL ECOSYSTEMSClimate is a fundamental driver of ongoing and future vegetation changes in New Mexico. Future changes in vegetation will affect the distribution and abundance of water resources in New Mexico. Major shifts in climate and vegetation across New Mexico's landscapes have occurred in the past, but the scale and rate of recent and projected climate change is probably unprecedented during the past 11,000 years. Recent warming, along with frequent and persistent droughts, have amplified the severity of vegetation disturbance processes like fire, physiological drought stress, and insect outbreaks, driving substantial changes in New Mexico vegetation since the year 2000. Ongoing and projected vegetation changes include growth declines, reduced canopy and ground cover, massive tree mortality episodes, and species changes in dominant vegetation-foreshadowing more severe changes to come if current warming trends continue as projected. Such major alterations of New Mexico vegetation likely will also have substantial ecohydrological feedbacks with New Mexico water resources. Since water-related environmental stresses occur in parallel with water supply shortages for people, such climate-change-driven water stress could lead to increasing conflict between managing declining water available for human use (e.g., irrigation) and retaining "wild" water for the maintenance of historical ecosystems.

Use of observed hydroclimatic trends to constrain projections of snowmelt season runoff in the Rio Grande headwaters

“…Even the sign of projected water supply changes is not consistent across different models and simulations. Much of the uncertainty derives from the wide spread of projections of regional precipitation change in southwestern mountains (Dunbar et al, 2022; IPCC, 2021; Udall & Overpeck, 2017). Reducing the uncertainty in future projections of streamflow is of critical importance for guiding difficult policy discussions as water authorities consider the possibility of significant declines in water supplies across the semiarid west (Lehner et al, 2019; Samimi et al, 2022; Udall & Overpeck, 2017; Wheeler et al, 2022).…”