Climate and Groundwater at Pecos National Historical Park, Water Year 2021

This report covers water year 2021, October 2020 through September 2021.

Pecos National Historical Park. National Park Service.

Climate and water together shape ecosystems and what they provide, especially in dry and semi-dry places, so tracking changes in climate, groundwater and surface water is key to judging the condition of a park's natural resources, and often its cultural ones. At Pecos National Historical Park in New Mexico, scientists with the Park Service's Southern Plains Inventory and Monitoring Network measure key "vital signs" year after year, much as a doctor tracks a patient's, to give managers early warning of problems. Climate and groundwater are reported together because they are closely linked, by water year: water year 2021 ran from October 2020 through September 2021.

Mission church at Pecos National Historical Park NPS.

Weather or climate? Weather is the conditions at a given moment, such as rain, snow, or a hot or freezing day. Climate is the pattern of weather at a place over seasons to years, and it is the main driver of ecological processes.

How climate is measured

Since 1916 the park has run a National Oceanic and Atmospheric Administration Cooperative Observer Program weather station (Pecos National Monument #296676). It usually provides a reliable long-term record, but in water year 2021 it was missing data on 135 days. This report therefore uses GRIDMET, a gridded climate dataset at 4-kilometer resolution built from station data, topography and other observed and modeled information, for both the year and the 30-year averages. GRIDMET values can differ from actual weather at a spot because of how many stations feed it and differences between a site's elevation and its grid cell's.

Groundwater wells and the weather station at Pecos National Historical Park. National Park Service.

Precipitation and temperature

• Precipitation: 14.39 inches (36.6 cm) fell, 1.65 inches below the 1991–2020 average. The shortfall came in the cool season, October through March, which got only 2.35 inches, less than half its average. The warm season, April through September, got 12.04 inches, 1.06 inches above average.
• Temperature: close to average. The average annual maximum was 66.0°F (18.9°C), about normal, and the average annual minimum 33.9°F (1.1°C), just 0.4°F below normal. Every month's average high and low was within 3.0°F of the 1991–2020 average.
• Drought: the reconnaissance drought index, which compares precipitation with potential evapotranspiration (the water that would be lost to evaporation and plant transpiration if water were not limited), showed water year 2021 was slightly drier than average.

Snowfall at Pecos National Historical Site NPS.

Groundwater

Groundwater is one of the Southwest's most critical resources, supplying drinking water, irrigating crops and feeding rivers, streams and springs. The New Mexico Bureau of Geology and Mineral Resources began monitoring two wells at the park in 2020: one at the trading post (WL-0206), measured continuously, and one on the Glorieta Battlefield Trail (WL-0207), measured once a year. The data are published through the Healy Collaborative Groundwater Monitoring Network.

Groundwater levels in water year 2021 were stable and fairly shallow:

The trading post average, for December 17, 2020, to August 26, 2021, includes readings taken while the well was pumping or had just pumped, which can lower the water level by up to 20 feet for a time, so the true resting level was probably a little higher. The 2020 readings there were also taken right after pumping, so the two years cannot be compared.

Depth to water at the two monitoring wells, water years 2020–2021. White circles mark manual readings taken during or just after pumping. National Park Service.

Sources

• Raymond, K., and A. Ray. 2023. "Climate and Water Monitoring at Pecos National Historical Park." Southern Plains Network, National Park Service. https://www.nps.gov/articles/000/peco-climate-water-monitoring21.htm
• The report cites Tsakiris and Vangelis (2005), European Water 9: 3–11, for the drought index. Climate data: GRIDMET via Climate Analyzer; groundwater data: Healy Collaborative Groundwater Monitoring Network, https://geoinfo.nmt.edu/resources/water/cgmn/
• The park's climate charts, produced with Climate Analyzer, are not reproduced here. Pictures an earlier version of this page left out were restored on 2026-09-26.