Climate and Water Monitoring at Big Bend National Park: Water Year 2024
Susan Singley, Kara Raymond, Tani Hubbard
Please cite this publication as:
Singley, S., K. Raymond, and T. Hubbard. 2026. Climate and Water Monitoring at Big Bend National Park: Water Year 2024. Science Report NPS/SR—2026/486. National Park Service, Fort Collins, Colorado. https://doi.org/10.36967/2318787
Abstract
The Chihuahuan Desert Inventory and Monitoring Network monitors climate, groundwater, and 18 springs each year at Big Bend National Park, Texas. We report on climate and water resources together because surface water conditions are closely related to climate conditions. Climate data, including temperature, precipitation, and reconnaissance drought index, from five weather stations are retrieved at The Climate Analyzer (climateanalyzer.org). Big Bend National Park staff use automated methods to monitor eight park groundwater wells. We retrieve data for a ninth well from the Texas Water Development Board database. We assess the condition of 18 springs, measure spring discharge and wetted extent (area that contained water), collect core water quality and water chemistry data, note any wetland plants and invasive plants and animals, and sample for environmental DNA (eDNA) to detect rare species, invasive species, and pathogens. Each spring is somewhat unique, and Texas has not adopted water quality standards that apply across the diversity of springs in the state. We collect water quality data at the springs to form a baseline reference of natural variance. Overall, there was less total annual rainfall than average, though higher than average precipitation in October and November occurred at three of the weather stations. The drought index indicated the park was drier than average for the fifth year in a row. The park was generally warmer than average, and the number of extremely hot days increased. Average groundwater levels decreased in seven wells, and three of those had their lowest water level since monitoring began. The other two wells had small increases in water levels. We were able to measure wetted area at 15 springs, nine of which were drier than in other years, while the other six were similar to prior measurements. Bois D’Arc Spring was completely dry. There was significant vegetation trampling and grazing by horses at Painted Hills Spring, heavy cattle and horse trampling at Solis Spring, trash and human trampling at De La Ho Spring, and human trampling at Mule Ears Spring. We observed new wetland plants at Cattail Falls (flatsedge) and Chilicotal Spring Complex (centaury) and new invasive plants at Solis Spring (Lehmann lovegrass) and Shelf Spring (buffelgrass). We detected Rio Grande leopard frogs in eDNA samples from eight of the springs. In five of these springs, we also detected chytrid. Red spotted toad was detected in one eDNA sample at Tiptoe Spring.
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Overview
Together, climate and hydrology shape ecosystems and the services they provide, particularly in arid and semi-arid ecosystems. Understanding changes in climate, groundwater, and surface water is key to assessing the condition of park natural resources—and often, cultural resources.
At Big Bend National Park (Figure 1), Chihuahuan Desert Inventory and Monitoring Network scientists study how ecosystems may be changing by taking measurements of key resources, or “vital signs,” year after year—much as a doctor keeps track of a patient’s vital signs. This long-term ecological monitoring provides early warning of potential resource problems, allowing managers to mitigate them before they become worse. At Big Bend National Park, we monitor climate, groundwater and springs, among other vital signs. Surface water and groundwater conditions are closely related to climate conditions. Because they are better understood together, we report on climate in conjunction with water resources. Reporting is by water year (WY), which begins in October of the previous calendar year and goes through September of the water year (e.g., WY2024 runs from October 2023 through September 2024). This article reports the results of climate and water monitoring at Big Bend National Park in WY2024.
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Climate and Weather
There is often confusion over the terms “weather” and “climate.” In short, weather describes short-term meteorological conditions (e.g., it’s currently raining or snowing, it’s a hot or frigid day), and climate reflects patterns of weather at a given place over longer periods of time (seasons to years). Climate is the primary driver of ecological processes on Earth. Climate and weather information provide context for understanding the status or condition of other park resources.
Methods
We report on five National Oceanic and Atmospheric Administration Cooperative Observer Program (NOAA COOP) weather stations at Big Bend National Park (Table 1, Figure 1). These stations provide reliable, long-term climate datasets for analyses in this climate and water report. The long-term averages used for comparison in this report are from NOAA and are based on 1991–2020 data, except averages from the Rio Grande Village Texas station, which are based on 2006–2020 data because the station was established in 2006. Data from these stations are accessible through The Climate Analyzer.
| Station Name | Station ID# | Elevation (ft) | Year Established |
|---|---|---|---|
| Chisos Basin | 411715 | 5300 | 1943 |
| Panther Junction | 416792 | 3740 | 1955 |
| Persimmon Gap | 416959 | 2870 | 1952 |
| Castolon | 411524 | 2170 | 1947 |
| Rio Grande Village Texas | 417624 | 1857 | 2006 |
Results
Precipitation and Air Temperature–Chisos Basin (COOP)
Highlights: Annual precipitation was well below average despite October and November being very wet. Temperatures were hotter than average, with nearly three times more extremely hot days.
Annual precipitation at the Chisos Basin station in WY2024 was 11.33″ (28.78 cm), 7.00″ (17.78 cm) less than the 1991–2020 average. WY2024 started wetter than average; the October precipitation total (Figure 2) was nearly three times the average, and November received over 50% more precipitation than average. However, monthly precipitation totals for the rest of the water year were substantially below average, except for July, which was slightly wetter. The largest rainfall deficits occurred in June and August, which received 2.45″ (6.22 cm) and 2.41″ (6.12 cm) less than average, respectively. Extreme daily rainfall events (≥1.00″; 2.54 cm) occurred on 2 days, half the average annual frequency of 4 days. The two extreme rainfall events occurred on 02 October 2023 (1.60″; 4.06 cm) and 06 July 2024 (1.59″; 4.04 cm). The mean annual maximum temperature at the Chisos Basin station in WY2024 was 75.0°F (23.9°C), 1.5°F (0.8°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 53.6°F (12.0°C), 1.3°F (0.7°C) above average. Mean monthly maximum and minimum temperatures in WY2024 varied up to 5.5°F (3.1°C, see May as an example) relative to the 1991–2020 monthly averages (Figure 2). Mean monthly maximum temperatures were warmer than average in every month except November and March. Mean monthly minimum temperatures were warmer than average in every month except January, March, and July. Extremely hot temperatures (≥90.0°F; 32.2°C) occurred on 60 days in WY2024, nearly triple the average frequency of 22.1 days. Extremely cold temperatures (≤30.0°F; −1.1°C) occurred on 14 days, 5 less than the average frequency of 18.9 days.
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Precipitation and Air Temperature–Panther Junction (COOP)
Highlights: Precipitation was substantially below average most of the year, but 50% greater than average in October, November, and July. Overall, temperatures were warmer, and there were more than twice as many extremely hot days than average.
Annual precipitation at the Panther Junction station in WY2024 was 8.25″ (20.96 cm), 4.75″ (12.07 cm) less than the 1991–2020 annual average. Monthly precipitation totals (Figure 3) for October, November, and July were approximately 50% greater than the long-term averages. Precipitation during all other months was substantially less than average. December and April were completely dry, and minimal precipitation occurred in March and May. The largest monthly precipitation deficits occurred in May and August, which received 1.29″ (3.28 cm) and 1.80″ (4.57 cm) less than average, respectively. Extreme daily rainfall (≥1.00″; 2.54 cm) occurred on 1 day, less than the average annual frequency of 2.5 days. This event occurred on 07 July 2024 (1.33″; 3.38 cm). The mean annual maximum temperature at the Panther Junction station in WY2024 was 81.7°F (27.6°C), 2.9°F (1.6°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 57.1°F (13.9°C), 3.0°F (1.7°C) above average. Mean monthly maximum and minimum temperatures in WY2024 (Figure 3) differed by as much as 7.4°F (4.1°C; see May as an example) relative to the 1991–2020 monthly averages (Figure 3). Mean monthly maximum and minimum temperatures were above average in every month except two: the mean maximum was below average in November, and the mean minimum was below average in January. Extremely hot temperatures (≥98.0°F; 36.7°C) occurred on 56 days in WY2024, over twice the average frequency of 25 days. Extremely cold temperatures (≤31.0°F; −0.6°C) occurred on 12 days, 10 less than the average frequency of 22.1 days.
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Precipitation and Air Temperature–Persimmon Gap (COOP)
Highlights: October and November were very wet, but most of the water year was drier than average. Overall, temperatures were warmer than average, and there were nearly twice as many extremely hot days.
Annual precipitation at the Persimmon Gap station in WY2024 was 5.76″ (14.63 cm), 5.09″ (12.93 cm) less than the 1991–2020 annual average. WY2024 started wetter than average; the October precipitation total was 85% more than the 1991–2020 average and November received over three times the average amount of rain. Monthly precipitation totals (Figure 4) for the rest of the water year were substantially below average, except for February, which was slightly wetter. May was completely dry. The largest deficits occurred in July and September, which received 1.50″ (3.81 cm) and 1.49″ (3.78 cm) less than average, respectively. There were no extreme daily rainfall events (>1.00″; 2.54 cm) in WY2024 compared to the average annual frequency of 2.4 days. The mean annual maximum temperature at the Persimmon Gap station in WY2024 was 84.6°F (29.2°C), 1.6°F (0.9°C) above the 1991–2020 average. The mean annual minimum temperature in WY2024 was 55.8°F (13.2°C), 2.1°F (1.2°C) above average. Mean monthly maximum and minimum temperatures in WY2024 varied by up to 4.8°F (2.7°C, see October as an example) relative to the 1991–2020 monthly averages (Figure 4). Mean monthly maximum temperatures were warmer than average in every month except November and January. Mean monthly minimum temperatures were warmer than average in every month except January and March. Extremely hot temperatures (≥103.0°F; 39.4°C) occurred on 42 days in WY2024, nearly twice the average frequency of 22.2 days. Extremely cold temperatures (≤28.0°F; −2.2°C) occurred on 15 days, about two less than the average frequency of 16.6 days.
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Precipitation and Air Temperature–Castolon (COOP)
Highlights: Castolon received about two thirds the average annual precipitation, mostly coming in October and November. High temperatures were cooler than average in the winter and warmer than average in the summer. Low temperatures were warmer than average most of the year.
Annual precipitation at the Castolon station in WY2024 was 6.61″ (16.79 cm), 3.25″ (8.26 cm) less than the 1991–2020 annual average. WY2024 started wetter than average; the October precipitation total was over twice the 1991–2020 average and November received 69% more precipitation than average (Figure 5). May and July totals were slightly above average. Precipitation totals in all other months were substantially less than average, with December, March, and April being completely dry. The largest monthly rainfall deficits occurred in June, August, and September, which received 1.06–1.16″ (2.69–2.95 cm) less than average. Extreme daily rainfall events (≥1.00″; 2.54 cm) occurred on 2 days, the same as the average annual frequency of 2.1 days. Extreme rainfall events occurred on 24 October 2023 (1.22″; 3.10 cm) and 06 July 2024 (1.59″; 4.04 cm). The mean annual maximum temperature at the Castolon station in WY2024 was 88.9°F (31.6°C), 0.5°F (0.3°C) above average. The mean annual minimum temperature in WY2024 was 59.2°F (15.1°C), 2.1°F (1.1°C) above average. Mean monthly maximum and minimum temperatures in WY2024 varied up to 5.4°F (3.0°C; see November as an example) relative to the 1991–2020 monthly averages (Figure 5). Mean monthly maximum temperatures were generally cooler than average in the cool season (October–March) and warmer than average during the warm season (April–September). Mean monthly minimum temperatures were warmer than average in all months except January and March. Extremely hot temperatures (≥108.0°F; 42.2°C) occurred on 29 days in WY2024, 4 more than the average frequency of 24.7 days. Extremely cold temperatures (≤30.0°F; −1.1°C) occurred on 18 days, similar to the average frequency of 18.7 days.
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Precipitation and Air Temperature–Rio Grande Village Texas (COOP)
Highlights: Rio Grande Village had a very dry year compared to average. Overall, temperature highs and lows were above average, and there were twice as many extremely hot days.
Annual precipitation at the Rio Grande Village Texas station in WY2024 was 4.48″ (11.38 cm), 7.58″ (19.25 cm) less than the long-term average. Only December and July precipitation totals were similar to the 2006–2020 averages (Figure 6). All other months received substantially less precipitation than average. March through May was completely dry. The largest monthly precipitation deficits occurred in May, June, August, and September, receiving 1.20–1.53″ (3.05–3.89 cm) less than average. There were no extreme daily rainfall events (>1.00″; 2.54 cm) in WY2024, less than the average annual frequency of 1.5 days. The mean annual maximum temperature at the Rio Grande Village Texas station in WY2024 was 91.5°F (33.0°C), 1.9°F (1.1°C) above the 2006–2020 average. The mean annual minimum temperature in WY2024 was 56.0°F (13.3°C), 1.5°F (0.8°C) above average. Mean monthly maximum and minimum temperatures in WY2024 varied up to 6.0°F (3.4°C; see May as an example) relative to the long-term monthly averages (Figure 6). Mean maximum monthly temperatures were warmer than average in every month except November, January, and March. Mean monthly minimum temperatures were warmer than average in every month except January and March. Extremely hot temperatures (≥109.0°F; 42.8°C) occurred on 55 days in WY2024, nearly twice the average frequency of 30 days. Extremely cold temperatures (≤26.0°F; −3.3°C) occurred on 20 days, 4 less than the average frequency of 24.3 days.
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Drought
Highlight: The park was drier than average in WY2024 for the fifth consecutive year except at Chisos Basin, which has been drier than average for three years in a row.
Reconnaissance drought index (Tsakiris and Vangelis 2005) provides a measure of drought severity and extent relative to the long-term climate. It is based on the ratio of average precipitation to average potential evapotranspiration (the amount of water loss that would occur from evaporation and plant transpiration if the water supply was unlimited) over short periods of time (seasons to years). The reconnaissance drought indices for Big Bend National Park indicate that WY2024 was drier than the 1991–2024 average for the fifth consecutive year from the perspective of both precipitation and potential evapotranspiration at all monitoring locations except Chisos Basin, which has been drier than average for three consecutive years (Figures 7–11).
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Groundwater
Groundwater is one of the most critical natural resources of the American Southwest, providing drinking water, irrigating crops, and sustaining rivers, streams, and springs throughout the region.
Methods
Groundwater at Big Bend National Park is monitored in nine wells. Eight wells have been monitored by park staff since 2012 using automated methods: Contractor’s, Gallery, Gambusia, K-Bar #6, K-Bar #7, Oak Springs #1, T-3, and Th-10. One well, Panther Junction #10, has been monitored by the Texas Water Development Board (TWDB) since 2007 using automated methods. TWDB data are available at the TWDB Database.
Results
Highlights: Recent declines in groundwater levels continued across seven wells, three of which hit their lowest water level on record. Water levels in T-3 and TH-10 wells rose slightly.
Average groundwater levels in seven wells decreased between WY2023 and WY2024 (based on a subset of available WY2023 data): Contractor’s, Gallery, Gambusia, K-Bar #6, K-Bar #7, Oak Springs #1, and Panther Junction #10 wells (Table 2, Figure 12). Decreases were ≤1.32 ft (0.40 m) except at Panther Junction #10 well, which decreased 12.39 ft (3.78 m). Average water level in wells T-3 and TH-10 rose ≤0.25 ft (0.08 m) since WY2023. Three wells recorded their lowest water level in the monitoring record in WY2024: Gallery, Gambusia, and Oak Springs #1 wells.
| State Well | Area of Park | Wellhead Elevation (ft) |
Mean Depth to Water (ft bgs) |
Mean Water Level Elevation (ft amsl) |
Elevation Change from WY2023 (± ft) |
Elevation Change (± ft) from Earliest Recorded Water Level (year) |
|---|---|---|---|---|---|---|
| Gambusia | Rio Grande | 1855.00 | 6.52 | 1848.48 | −0.78 | −2.52 (1984) |
| Gallery | Rio Grande | 2126.00 | 19.66 | 2106.34 | −1.32 | −9.14 (1969) |
| K-Bar #7 | Panther Junction | 3460.00 | 68.04 | 3391.96 | −1.15 | 5.55 (1984) |
| TH-10 | Panther Junction | 3466.00 | 42.87 | 3423.13 | 0.19 | −7.28 (1967) |
| K-Bar #6 | Panther Junction | 3498.00 | 106.82 | 3391.18 | −1.21 | 0.09 (1984) |
| T-3 | Panther Junction | 3617.20 | 97.27 | 3519.93 | 0.25 | 10.89 (1964) |
| Panther Junction #10 | Panther Junction | 3887.00 | 163.79 | 3723.21 | −12.39 | −2.29 (2006) |
| Contractor’s A | Chisos Basin | 3753.00 | 42.50 | 3710.50 | −1.26 B | −1.00 (1971) |
| Oak Spring #1 A | Chisos Basin | 4165.00 | 61.93 | 4103.07 | −0.84 C | −28.10 (1989) |
A Water levels are based on one manual measurement.
B Change in elevation compared to a single manual measurement in WY2021 because of missing data.
C Change in elevation compared to WY2022 because of missing data.
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Rio Grande Wells
Water levels in Gallery and Gambusia are consistently shallow and have demonstrated low variability; water level changes have ranged within 7.99 ft (2.44 m) and 3.08 ft (0.94 m), respectively. Both wells are close to the Rio Grande and respond to changes in river flow, often increasing in late summer or fall following high flow events. However, this signal is weaker at Gambusia, which is likely regulated by nearby springs.
Panther Junction Wells
Water level elevations in wells K-Bar #6 and K-Bar #7 have been very similar for the entire monitoring record as they are 0.45 mi (0.72 km) apart and completed in the same aquifer. Water levels in both wells peaked in 2019 following a large rain event in 2018, and their water levels have been slowly declining since then. T-3 well exhibits similar periods of increasing and decreasing water levels even though it is >130 ft (39.6 m) higher than the K-Bar wells. Water level in Panther Junction #10 well is the most variable of the Big Bend National Park monitoring wells, with a range of 143 ft (43.6 m) in water level elevation change over the monitoring record. This is likely due to rapid infiltration of rain though fractured volcanic rock, which then seeps to deeper aquifers. TH-10 well water level has been very stable, showing only 13.60 ft (4.14 m) of variation in water level over the monitoring record, with muted responses to large rain events compared to the other Panther Junction wells.
Chisos Basin Wells
Water levels in Contractor’s well appear to respond quickly to rain events, indicating rapid infiltration similar to Panther Junction #10 well; however, the response in Contractor’s well is much more muted. Water levels in Oak Springs #1 well showed the greatest decline since the first measurement in 1989 but water levels have been stable with little variation since 2011 when more frequent monitoring began.
Springs
Background
Springs, seeps, and tinajas (discrete pools in a rock basin or impoundments in bedrock) are small, relatively rare biodiversity hotspots in arid lands. They are the primary connection between groundwater and surface water and are important water sources for plants and animals. For springs, the most important questions we ask are about persistence (How long was there water in the spring?) and water quantity (How much water was in the spring?). WY2024 springs sampling at Big Bend National Park occurred between 01 February and 20 February 2024. Water persistence is monitored continuously throughout the water year, but in this report, we only present WY2024 persistence data up to the sampling visit date for each spring.
Methods
Chihuahuan Desert Network springs monitoring is organized into the four modules described below (see McIntyre et al. 2018 for additional details) and eDNA inventories. All data have undergone certification processes to ensure they have been verified and validated for accuracy, are complete, and are fully documented. Data used in this report are available to park staff on the NPS DataStore and can be provided upon request.
Site Characterization
This module provides context for interpreting change in the other modules. We record GPS locations, draw a site diagram, and describe the spring type (e.g., helocrene, limnocrene, rheocrene, or tinaja) and its associated vegetation in this module. Helocrene springs emerge as low-gradient wetlands, limnocrene springs emerge as pools, and rheocrene springs emerge as flowing streams. This module is completed once every five years or after significant events.
Site Condition
We estimate the level of natural and anthropogenic disturbances and the level of stress on vegetation and soils at the spring on a scale of 1–4, where 1 = undisturbed, 2 = slightly disturbed, 3 = moderately disturbed, and 4 = highly disturbed. Types of natural disturbances can include flooding, drying, fire, wildlife impacts, windthrow of trees and shrubs, beaver activity, and insect infestations. Anthropogenic disturbances can include roads, off-highway vehicle trails, hiking trails, livestock and feral-animal impacts, removal of invasive non-native plants, flow modification, and other evidence of human use of the spring site. We take repeat photographs from the same location and perspective to show the spring and its landscape context. We note the presence of certain obligate wetland plant species (plant species that almost always occur only in wetlands), facultative wetland plant species (plant species that usually occur in wetlands, but also occur in other habitats), and invasive non-native crayfish and American bullfrog (Rana catesbeiana). We also record the density of invasive non-native plants using a qualitative scale (1–5 plants, scattered patches, evenly distributed patches, or a matrix). We complete the site condition module during each springs monitoring visit.
Water Quantity
We measure the persistence of surface water, amount of spring discharge, and wetted extent (area that contained water). To estimate persistence, we analyze the variance of temperature measurements taken by two logging thermometers placed at or near the orifice (spring opening). Because water mediates variation in diurnal temperatures, data from a submerged sensor will show less daily variation than data from an exposed, open-air sensor; this tells us when the spring was wet or dry. Surface discharge is measured with a timed sample of water volume. Wetted extent is a systematic measurement of the physical length (up to 100 m), width, and depth of surface water. It is assessed using a technique for either standing water (e.g., limnocrene and helocrene springs) or flowing water (e.g., rheocrene springs). We complete discharge and wetted extent measurements during each visit when possible. Water persistence measurements are continuous throughout the year.
Water Quality
We measure core water quality and water chemistry parameters. Core water quality parameters include water temperature, pH, specific conductivity (a measure of dissolved compounds and contaminants), dissolved oxygen (how much oxygen is present in the water), and total dissolved solids (an indicator of potentially undesirable compounds). Discrete measurements of these parameters are collected with a multiparameter meter. If the meter fails calibration checks, we do not present data. Water chemistry is assessed by collecting surface water samples and estimating the concentration of major ions with a photometer in the field. These parameters are collected at one or more sampling locations within a spring. Data are presented only for the primary sampling location within each spring. Each perennial spring is somewhat unique, and Texas has not adopted water quality standards that would apply across the diversity of springs described here. Ongoing, long-term data collection at each spring will improve our understanding of the natural range in water quality and water chemistry parameters for a given site. We complete the water quality module during each visit when possible.
eDNA Inventory of Rare and Invasive Species and Pathogens
We inventory rare species, invasive species, and pathogens in perennial springs using environmental DNA (eDNA) techniques. In 2023 and 2024, four or more water samples (250 mL/sample) were collected and filtered (0.45 µm) from each spring and then preserved in ethanol prior to DNA extraction and analysis by the Goldberg Lab at Washington State University. Our target organisms for the inventory include American bullfrog (Rana catesbeiana), chytrid fungus (Batrachochytrium dendrobatidis), ranavirus (Iridoviridae), red spotted toad (Bufo punctatus), Rio Grande leopard frog (Rana berlandieri), and Woodhouse’s toad (Anaxyrus woodhousii).
Results
Bois D’Arc Spring
Highlights: The spring and all previously wet orifices were dry when we visited in February 2024. The temperature sensor was buried in sediment, so persistence data may be unreliable.
Bois D’Arc Spring (Figures 13 and 14) is a rheocrene spring (a spring that emerges into one or more stream channels). The spring is located within a bedrock canyon on the north side of the Chisos Mountains. It forms an intermittent channel that has ranged in length from 0 m to over 100 m in recent years. The WY2024 visit occurred on 01 February 2024, and the spring was dry.
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Site Condition
In WY2024, we rated Bois D’Arc Spring slightly disturbed by feral animals because there was an aoudad (Ammotragus lervia) carcass observed near the spring (rated undisturbed to slightly disturbed in the past); slightly disturbed by recent flooding based on fresh recent gravel deposits and uprooted vegetation within the channel (rated undisturbed to moderately disturbed in the past); highly disturbed by drying because there was no water in any of the previously wetted orifices, and there were upland species in the riparian area (rated undisturbed to highly disturbed in the past); and slightly disturbed by wildlife, with scat and evidence of animal bedding (rated undisturbed to moderately disturbed in the past; Figure 15). No other natural or human-caused disturbances were observed at Bois D’Arc Spring in WY2024.
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As in past years, we did not observe invasive non-native crayfish or American bullfrog (Rana catesbeiana) at Bois D’Arc Spring in WY2024. We found one invasive non-native plant species at the spring: scattered patches of Lehmann lovegrass (Eragrostis lehmanniana, scattered to evenly distributed patches observed in 2018–2023). We observed two obligate/facultative wetland plant species: monkeyflower (Mimulus sp., a forb observed in 2018–2021) and mule-fat (Baccharis salicifolia, a shrub observed in 2019).
eDNA Inventory of Rare and Invasive Species and Pathogens
In WY2024, four water samples were collected from isolated pools of water near Bois D’Arc Spring. Similar to WY2023, none of our target organisms were detected.
Water Quantity
Sensors are deployed and data are downloaded during our annual visit; the dates of these visits are indicated by black diamonds in the persistence graph (Figure 16). The temperature sensor indicated that Bois D’Arc Spring was wetted (contained water) for all 124 days (100%) measured in WY2024 up to the visit but the sensor was buried in sediment, so the readings may be false, especially since the spring was completely dry when we visited. In prior water years, the spring was wetted 5.8–88.5% of the days measured across entire years.
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Discharge was not measured in WY2024 at the primary sampling location since the spring was dry. Discharge estimates ranged from 0.8–7.8 L/min (0.2–2.1 gal/min) in 2019–2020 (Table 3). The flowing water method for wetted extent was not used in WY2024 because the spring was dry. Past data are summarized in Table 4.
| Sampling Location | WY2024 Mean (Range of Prior Means) |
Prior Years Measured (# of Visits with Measurements) |
|---|---|---|
| 005 | c.n.s. (0.8–7.8) | 2019–2020 (2) |
| Measurement | WY2024 Value (Range of Prior Values/Means) |
Prior Years Measured (# of Visits with Measurements) |
|---|---|---|
| Width (cm) | c.n.s. (23.7–93.1) | 2018–2023 (5) |
| Depth (cm) | c.n.s. (0.9–8.9) | 2018–2023 (5) |
| Length (m) | c.n.s. (2.2–100.0) | 2018–2023 (5) |
Water Quality
Core water quality data and water chemistry data were not collected at the primary sampling location in WY2024 because the spring was dry. Past data are summarized in Tables 5 and 6.
| Sampling Location | Parameter | WY2024 Value (Range of Prior Values) |
Prior Years Measured (# of Measurements) |
|---|---|---|---|
| 002 | Dissolved oxygen (mg/L) | c.n.s. (7.66–11.81) | 2021–2023 (2) |
| 002 | pH | c.n.s. (7.86–9.64) | 2021–2023 (2) |
| 002 | Specific conductivity (µS/cm) | c.n.s. (240.3–319.5) | 2021–2023 (2) |
| 002 | Temperature (°C) | c.n.s. (9.5–11.7) | 2021–2023 (2) |
| 002 | Total dissolved solids (mg/L) | c.n.s. (156–208) | 2021–2023 (2) |
| Sampling Location | Parameter | WY2024 Value (Range of Prior Values) |
Prior Years Measured (# of Measurements) |
|---|---|---|---|
| 002 | Alkalinity (CaCO3) | c.n.s. (75–90) | 2021–2023 (2) |
| 002 | Calcium (Ca) | c.n.s. (22–52) | 2021–2023 (2) |
| 002 | Chloride (Cl) | c.n.s. (0–4) | 2021–2023 (2) |
| 002 | Magnesium (Mg) | c.n.s. (b.d.l.–10) | 2021–2023 (2) |
| 002 | Potassium (K) | c.n.s. (0.0–1.8) | 2021–2023 (2) |
| 002 | Sulphate (SO4) | c.n.s. (0) | 2021–2023 (2) |
Cattail Falls
Highlights: The spring contained water when we visited and normally has water year round, though persistence data are unavailable for WY2024. We observed flatsedge, a wetland plant that had not previously been detected. Rio Grande leopard frogs were detected in all eDNA samples and chytrid fungus in one. The site is heavily trampled by hikers.
Cattail Falls (Figures 17 and 18) is a rheocrene spring (a spring that emerges into one or more stream channels). The spring is in Cattail Canyon on the northwest side of the Chisos Mountains. It begins high in the mountains and flows over a steep pouroff into a wide pool. A channel flows out of the pool, forming deep, clear plunge pools surrounded by boulders and dense vegetation. The springbrook has consistently reached 95–98 m in length (measured from the base of the falls) in recent years. The WY2024 visit occurred on 06 February 2024, and the spring contained water.
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Site Condition
In WY2024, we rated Cattail Falls as highly disturbed by hiking trails because there was trampling of riparian vegetation by hikers (Figure 19). A popular hiking trail leads to the spring and crosses the springbrook. Vegetation cover is reduced on approximately 50% of the area surrounding the pool at the base of the falls, especially where the trail crosses the springbrook. In the past, we rated the spring moderately to highly disturbed by human use and hiking trails. We also rated the spring as slightly disturbed by windthrow as there were downed trees in and across the springbrook (rated undisturbed to moderately disturbed in the past). No other natural or human-caused disturbances were observed at Cattail Falls in WY2024. Native frogs, tadpoles, and frog eggs were observed in the pools in WY2024.
NPS
As in past years, we did not observe invasive non-native crayfish or American bullfrog (Rana catesbeiana) at Cattail Falls in WY2024, nor did we find any invasive non-native plants at the spring. We observed six obligate/facultative wetland plant species: bluestem (Andropogon sp., a grass observed in 2018–2023); cattail (Typhaceae, observed in 2018–2023); flatsedge (Cyperus sp., not previously observed); lobelia (Lobelia sp., a forb observed on three site visits between 2017 and 2023); maidenhair fern (Adiantum sp., observed in 2018–2023); and a member of the rush family (Juncaceae, observed in 2018–2023).
eDNA Inventory of Rare and Invasive Species and Pathogens
In WY2024, 10 water samples were collected from Cattail Falls. Rio Grande leopard frog was detected in all 10 samples and chytrid fungus, the pathogen responsible for chytridiomycosis in amphibians, was detected in one sample. In WY2023, chytrid was detected in five of the 10 water samples collected. We were unable to test for Rio Grande leopard frog in WY2023 samples.
Water Quantity
Sensors are deployed and data are downloaded during our annual visit; the dates of these visits are indicated by black diamonds in the persistence graph (Figure 20). Temperature sensor data are missing because of sensor failure, so there is no estimate of persistence for WY2024. In prior water years, the spring was wetted (contained water) 96.3–100% of the days measured across entire years.
NPS
Discharge was estimated at 33.3 ± 2.3 L/min (8.8 ± 0.6 gal/min), which was lower than previous measurements of 40.1–72.1 L/min (10.6–19.0 gal/min) in 2018–2023 (Table 7). Wetted extent was evaluated using a method for flowing water. Overall, the wetted extent of Cattail Falls was comparable to prior years. The total springbrook length was 96.8 m (317.6 ft), which is consistent with the historical range of 94.7–98.9 m (310.7–324.5 ft). Width and depth along the springbrook averaged 3.6 m (11.8 ft), and 12.4 cm (4.9 in), respectively, both similar to prior means. (Table 8).
| Sampling Location | WY2024 Mean (Range of Prior Means) |
Prior Years Measured (# of Visits with Measurements) |
|---|---|---|
| 003 | 33.3 ± 2.3 (40.1–72.1) | 2018–2023 (6) |
| Measurement | WY2024 Value (Range of Prior Values/Means) |
Prior Years Measured (# of Visits with Measurements) |
|---|---|---|
| Width (m) | 3.6 ± 4.0 (3.0–4.2) | 2018–2023 (6) |
| Depth (cm) | 12.4 ± 4.6 (6.1–16.3) | 2018–2023 (6) |
| Length (m) | 96.8 (94.7–98.9) | 2018–2023 (6) |
Water Quality
Core water quality (Table 9) and water chemistry (Table 10) data were collected at the primary sampling location on the river left edge of the main pool at the base of the falls in WY2024. Dissolved oxygen, pH, and temperature were all within the ranges of prior measurements. Specific conductivity and total dissolved solids values were higher than in prior years. Values for chloride, magnesium, and potassium were within ranges of prior values, while values for alkalinity, calcium, and sulphate were higher.
| Sampling Location | Parameter | WY2024 Value (Range of Prior Values) |
Prior Years Measured (# of Measurements) |
|---|---|---|---|
| 001 | Dissolved oxygen (mg/L) | 6.42 (3.44–8.49) | 2018–2023 (6) |
| 001 | pH | 7.56 (7.04–8.10) | 2018–2023 (6) |
| 001 | Specific conductivity (µS/cm) | 489.9 (200.7–459.4) | 2018–2023 (6) |
| 001 | Temperature (°C) | 10.5 (9.5–14.6) | 2018–2023 (8) |
| 001 | Total dissolved solids (mg/L) | 318.4 (130.0–299.0) | 2018–2023 (6) |
| Sampling Location | Parameter | WY2024 Value (Range of Prior Values) |
Prior Years Measured (# of Measurements) |
|---|---|---|---|
| 001 | Alkalinity (CaCO3) | 180 (25–130) | 2018–2023 (6) |
| 001 | Calcium (Ca) | 58 (2–54) | 2018–2023 (6) |
| 001 | Chloride (Cl) | 10 (1–27) | 2018–2023 (6) |
| 001 | Magnesium (Mg) | 13 (7–14) | 2018–2023 (6) |
| 001 | Potassium (K) | 1.6 (1.3–1.9) | 2018–2023 (6) |
| 001 | Sulphate (SO4) | 126 (33–93) | 2018–2023 (6) |
Chilicotal Spring Complex
Highlights: The spring contained water year round and discharge was similar to the previous measurement. The site was highly disturbed by a recent flood. We observed the wetland plant centaury for the first time, and we detected Rio Grande leopard frogs and chytrid in eDNA samples.
Chilicotal Spring Complex (Figures 21 and 22) is a rheocrene spring (a spring that emerges into one or more stream channels). The spring complex is inside a drainage in the desert shrublands northeast of Chilicotal Mountain. It emerges from the side of a steep and densely vegetated bank, forming a springbrook that can reach up to 200–500 m in length, but is typically only accessible in the upper reaches. The WY2024 visit occurred on 15 February 2024, and the spring contained water.