The latest Water Supply Outlook Report is now available.
From the Summary:
“March 1 snowpack conditions again favored the southern and western New Mexico forecast basins, extending west into Arizona. Snow accumulation, particularly in the early part of February, resulted in above normal to normal Snow Water Equivalent measured in the Lower Rio Grande, Pecos, Rio Chama-Upper Rio Grande, and Canadian basins as of the most recent survey cycle. The most extensive mountains feeding the northern headwaters of the Rio Grande and San Juan basins in northern New Mexico and southern Colorado still hold below to well below normal Snow Water Equivalent, with conditions much improved over the last month. As of March 1, the well above normal snowpack conditions in the Zuni and Gila San Francisco basins were overwhelmed by drier conditions further north, leaving statewide Snow Water Equivalent totals at approximately 94% of the reference period normal for New Mexico after a brief period of above normal snowpack conditions early in the month. This is a significant statewide improvement since last month, with every major forecast basin aside from the Lower Rio Grande seeing dramatic snowpack gains from a series of notable February snowstorms.
Alongside these gains in Snow Water Equivalent, February monthly precipitation was uniformly above normal across New Mexico’s forecast basins, providing a more optimistic snapshot of statewide water supply conditions as compared to February 1. Every major basin in the state has seen improved cumulative water year-to-date precipitation totals compared to reference period normals, mostly from weather events occurring early in the month. The Gila San Francisco and Lower Rio Grande basins have now received normal to above normal cumulative precipitation. In the Pecos, water year-to-date precipitation is slightly below normal at 97% of the reference period median. The northern New Mexico and southern Colorado basins remain below normal for cumulative precipitation since October 1, 2023, when water year 2024 began. Statewide precipitation totals account for 88% of the reference period normal as of forecast publication on March 1, a large increase over last month. Despite a bleak start to water year 2024, winter precipitation gains throughout February have served to move conditions much closer toward 30-year normals across New Mexico.
Reservoir storagevolumes have increased over the last year in four of the six major New Mexico storage systems: the Rio Grande Headwaters, Rio Chama- Upper Rio Grande, Lower Rio Grande, and San Juan. These systems comprise the majority of New Mexico’s storage capacity for water users statewide and beyond, so this month’s increased storage represents a large gain over last year’s March 1 reservoir levels. Despite this improvement over 2023, storage still sat below to well below reference period medians as of March 1 in all forecast basins except the Rio Grande Headwaters in southern Colorado. This basin lies in the San Luis Valley, which currently holds 122% of the median basin-wide storage volume. Since the bulk of New Mexico reservoir capacity exists further downstream, considerable runoff will still be required to reach reference period normal storage volumes, particularly in the Canadian and Pecos systems. Rio Chama-Upper Rio Grande basin combined reservoir statistics remain impacted by dam maintenance at El Vado Reservoir, where minimal storage is available.
This third official forecast publication of water year 2024 sets the stage for future refinement of water supply expectations throughout the remainder of winter and is based upon observed conditions and model guidance as of the end of February. In several basins throughout New Mexico, March marks the start of the primary NRCS forecast period. With significant snowpack remaining in higher elevations and more northerly extents of the forecast area, March 1 official NRCS streamflowforecast volumes still represent a considerable range of possible flows for many locations. As is normal for forecast publication dates, these official March 1 NRCS forecasts will not account for any weather that has occurred throughout the state since February 29, 2024. These forecasts reflect the fact that the normal peak of statewide snowpack still lies in the weeks just ahead and additional snow accumulation, rain, winds, temperature patterns, and other climate events will impact melt, runoff, and streamflow results during the forecast period. Following snow and inclusive precipitation trends, forecast volumes at the 50% exceedance probability are improved over February 1 predictions in all but the Pecos basin, where basin-wide streamflow outlooks have in fact been reduced from last month. Observed monthly streamflowvolumes during winter can be challenging to interpret with respect to the reference period normal. These winter monthly totals largely represent storage water being reallocated between reservoirs to meet management objectives as opposed to new water entering the water supply from the natural water cycle. This is especially notable in highly managed watersheds such as the Rio Grande and Rio Chama. For parts of the Zuni and Gila- San Francisco basins, February streamflow volumes suggest that the runoff period for 2024 has begun.”
- Jaz Ammon, Water Supply Specialist (Hydrologic Technician)