Article

Climate and Water Monitoring at Amistad National Recreation Area: Water Year 2021

Cactus and shrubs on the side of a cliff with a wide river along it.
Amistad National Recreation Area lies between temperate and tropical climate zones and between the arid western U.S. and the more humid and wet eastern U.S. The Amistad Reservoir receives water from basins in the U.S. and Mexico, including the Rio Grande, the Pecos River, and the Devils River.

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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 Amistad National Recreation Area (NRA), Our Chihuahuan Desert 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 problems, allowing managers to mitigate them before they become worse. We monitor climate, weather, groundwater, reservoir level, and springs among other vital signs at the park.

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., WY2021 runs October 2020 through September 2021). Information is added to this page as it becomes available throughout the year. 

Two large circular clouds in the sky over a desert hill
Lenticular clouds at Amistad National Recreation Area

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Climate and Weather 

There is often confusion over the terms, "weather" and "climate." In short, weather describes instantaneous meteorological conditions (e.g., it's currently raining or snowing, it's a hot or frigid day). 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

Since 1964, Amistad NRA has operated a National Oceanic and Atmospheric Administration Cooperative Observer Program weather station (Amistad Dam #410225, Fig. 1). This station provides a reliable, long-term climate dataset used for analyses in this climate and water report. Data from this station are accessible through Climate Analyzer. 

Figure A. A map of Amistad National Recreation Area showing the location of a weather station and groundwater wells.
Figure 1. Weather stations and monitored groundwater wells at Amistad National Recreation Area.

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Recent Findings 

Precipitation

Annual precipitation at the Amistad Dam station in WY2021 was 15.45″ (39.2 cm; Figure 2), 3.98″ (10.1 cm) less than the 1991–2020 normal. This precipitation deficit occurred primarily in the cool season (October–March). Rainfall in the warm season (April–September) was near normal. Extreme daily rainfall events (>1″; 2.54 cm) occurred on 4 days, one less than the normal annual frequency. Extreme rainfall events occurred on December 31, 2020 (1.31″; 3.3 cm); May 1, 2021 (2.00″; 5.1 cm); July 6, 2021 (1.70″; 4.3 cm); and August 18, 2021 (1.71″; 4.3 cm).

Air Temperature

Mean annual maximum air temperatures in WY2021 were 0.2°F (0.1°C) warmer than the normal 81.1°F (27.3°C), and mean annual minimum air temperatures were 1.0°F (0.6°C) cooler than the normal minimum of 58.0°F (14.4°C; normal is based on means from 1991–2020). Mean monthly maximum and minimum temperatures were generally near normal (Figure 2); however, large temperature deviations were observed in November, which was substantially warmer than normal, and February, which was substantially cooler than normal. No days recorded extremely hot temperatures (>102°F; 38.8°C) in WY2021 compared to the normal frequency (21.8 days). Extremely cold temperatures (<35°F;1.7°C) occurred on 30 days, almost twice the normal frequency (16.6 days).

A climogram showing water year 2021 monthly precipitation and maximum and minimum temperature compared to normal.
Figure 2. Climogram showing monthly precipitation and average maximum and minimum temperature, WY2021 and the 1991–2020 normals from Amistad Dam. 

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Drought

Reconnaissance drought index 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 (water loss due to evaporation and plant transpiration) over short periods of time (seasons to years). The reconnaissance drought index for Amistad NRA indicates WY2021 was a slightly drier year from the perspective of both precipitation and evaporative demand (amount of water evaporated; Figure 3).

A bar graph of a drought index compared to normal by water year from 1991 to 2021
Figure 3. Reconnaissance drought index, WY1991–2021, Amistad Dam. “N/A” = insufficient data to generate reliable estimates. 

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An aerial view of a river meeting a dam and the reservoir beyond it
Amistad Dam

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Reservoir Level

The Amistad International Reservoir was formed by the construction of Amistad Dam between 1964 and 1969. Reservoir level is not a Chihuahuan Desert Network vital sign; however, it is included in this report because the reservoir level has implications for park resources throughout Amistad NRA, including groundwater and springs.

Methods

The International Boundary and Water Commission (IBWC) has operated a water level gage at Amistad Reservoir (International Amistad Reservoir Storage Station Number 08-4508.00) since 1968 when filling began. The gage is located at the downstream end of the reservoir. Every 15 minutes, the gage collects water level data, which are available from the IBWC and the Texas Water Development Board (TWDB).

Recent Findings 

Mean reservoir level in WY2021 was 1068.24 feet above mean sea level (amsl) with a range of 1066.90 to 1073.76 feet amsl. Daily water level in WY2021 was on average 21.49 feet below the mean for 1991–2020 (Figure 4). The reservoir ranged from 51.2–65.3% full.

A line graph of reservoir water level (feet above mean sea level) in water year 2021 and the 30-year (1991 to 2020) normal daily mean, maximum and minimum levels.
Figure 4. Daily Amistad Reservoir water level elevation in water year 2021 and the 30-year (1991–2020) normal daily mean, maximum and minimum levels.

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Areservoir with desert plants on the bank and a bridge in the distance
Groundwater and reservoir levels interact at Amistad NRA.

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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

Amistad NRA groundwater is monitored using six wells in or near the recreation area (Figure 1). Each well is monitored annually by the Texas Water Development Board (TWDB) and the data are available at the Texas Water Development Board Groundwater Database.

Recent Findings 

Groundwater at the park was not monitored by TWDB in WY2021 due to Covid-19 disruptions to fieldwork. The most recent results are from February 25–27, 2020. Groundwater levels in the six monitored wells decreased between WY2019 and in WY2020 (Figure 5 and Table 1). These decreases were consistent with a 7.93-foot decline in reservoir level over the same period. Groundwater levels in wells 7033302, 7033508, 714021, and 7140307 are on the periphery of the reservoir and were ≤ 10.78 feet below the level of the reservoir. Water levels in wells 7017403 and 7140307 were both substantially higher than the reservoir level. They demonstrated a muted response to reservoir level because they are up gradient of the reservoir, adjacent to the Devils River and the Pecos River, respectively.

A line graph of groundwater well levels compared to reservoir levels from 1963 to 2021.
Figure 5. Water level elevation (feet above mean sea level) at six groundwater monitoring wells and Amistad Reservoir, 1964–2021, Amistad NRA.

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Springs

Background

Springs, seeps, and tinajas (small 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?).

Click on a spring below to view monitoring results.

Big Satan Canyon Spring
Dead Mans Canyon Spring
Indian Springs Canyon Spring
Mouth of the Pecos
A large narrow pool of water surround by rock faces.
Big Satan Canyon Spring at Amistad National Recreation Area, April 2018

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Recent Findings at Big Satan Canyon Spring

Big Satan Canyon Spring was last characterized in WY2018. Big Satan Canyon Spring was classified as a rheocrene spring (a spring that emerges as a flowing stream). This spring was a complex of six individual spring orifices. Cool and clear water flowed through a series of cracks and variable channels that ran a short distance and emptied into the adjacent Amistad Reservoir.

Site Condition

There was moderate disturbance from hiking trails. This is the first year that we noted trails to the spring. We noted slight disturbance from contemporary human use, drying, and wildlife (non-livestock), similar to past ratings. No crayfish or bullfrogs were observed.

The crew observed the following obligate/facultative wetland species/genera/families: bluestem (Andropogon sp.), fogfruit (Phyla sp.), mule-fat (Baccharis salicifolia), rush family (Juncaceae family), sedge family (Cyperaceae family), and spikerush (Eleocharis sp.). This was the first observation of mule-fat at the spring.

The crew observed two invasive plant species: yellow bluestem (Bothriochloa ischaemum) in evenly distributed patches and 1–5 tree tobacco (Nicotiana glauca) plants. There was a higher density of yellow bluestem than in previous years.

Water Quantity

The WY2021 visit occurred on April 14, 2021. Temperature sensors are not deployed at the site due to potential loss due to flooding and lake inundation. Discharge and wetted extent (a measure of length, width, and depth of surface water) were measured in prior years (Tables 2 and 3), but were not measured in WY2021 because the orifices were barely wetted (contained water).

Water Quality

Core water quality data were collected at two sampling locations in WY2021. Compared to previous years, dissolved oxygen was higher, and total dissolved solids and specific conductivity were slightly higher (Table 4). Water chemistry data were collected at one of the sampling locations in WY2021. Chloride levels were higher than in previous years, whereas other parameters were similar to WY2017–2018 samples (Table 5).

Big Satan Canyon Spring Data Tables

Download All Water Quality Data (Coming Soon)
A pool of greenish water in front of a rock face with large boulders around it.
Dead Mans Canyon Spring, Amistad National Recreation Area, April 2018.

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Recent Findings at Dead Mans Canyon Spring

Dead Mans Canyon Spring was last characterized in WY2018. This spring was classified as a rheocrene system, a spring that emerges as a flowing stream. It was also a hanging garden—a type of spring that emerges horizontally from a vertical surface or slope and creates a spring-fed plant colony that appears as a hanging garden. The water emerged several meters above the reservoir and the spring was about 25 m wide (82 ft) with 6 orifices. Cool and clear water flowed from the orifices (only one was not flowing) and algae was present in the pools.

Site Condition

The spring was not visited during WY2021.

A bar graph showing when the spring was wet from water years 2017 through 2021. The site was not visited during WY2021.
Figure 6. Water persistence at Dead Mans Canyon Spring in Amistad National Recreation Area.

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Water Quantity

Temperature sensors have not been retrieved since April 2019. The site was inaccessible due to low lake levels in WY2021 and site visits were cancelled in WY2020 due to COVID. Persistence data (whether the spring was wet or dry) are shown for prior years in Figure 6. A range of discharge and wetted extent data from prior years are shown in Tables 6 and 7.

Water Quality

The spring was not visited during WY2021. See Tables 8 and 9 for water quality value ranges from prior years.

Dead Mans Canyon Spring Data Tables

Download All Water Quality Data (Coming Soon)
Two people crouched down by a small pool of water in a rock lined basin and filled with algae
Indian Springs Canyon Spring, Amistad National Recreation Area, April 2018.

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Recent Findings at Indian Springs Canyon Spring

Indian Springs Canyon Spring was last characterized in WY2018. This spring was classified as a rheocrene spring, a spring that flows into a stream. Water flowed clear and cool from a single orifice into a small pool and eventually into the Amistad Reservoir. There was a thick algal mat present on the surface of much of the pool and submerged algae was found throughout.

Site Condition

There was moderate disturbance from feral animals and high disturbance from drying. Disturbance from feral animals has been observed previously but this is the first indication of disturbance that was attributable to drying. However, during the 2022 visit park staff stated that the emergence point may shift depending on lake levels; only a single potential emergence point was assessed in 2021. No crayfish or bullfrogs were observed.

The crew observed a single obligate/facultative wetland plant: fogfruit (Phyla sp.). This genus was also observed in WY2019.

The crew observed scattered patches of two invasive plants species: yellow bluestem (Bothriochloa ischaemum) and lilac chastetree (Vitex agnus-castus). We observed similar densities of both species in prior years.

A bar graph of water quantity in water years 2017 through 2020. The spring was largely dry in water year 2021.
Figure 7. Water persistence at Indian Springs Canyon Spring in Amistad National Recreation Area.

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Water Quantity

On the WY2021 visit (April 13, 2021), discharge and wetted extent were not measured because the spring was dry. However, during the 2022 visit, park staff said the emergence point may shift depending on lake levels; only a single potential emergence point was assessed in 2021. Tables 10–11 show prior year ranges of values for discharge and wetted extent. Temperature sensors indicated that the spring was wetted for 10 of 195 days (5.1%)—measured up to the WY2021 visit (Figure 7). In prior water years, the spring was wetted 15.8–86.8% of the days measured.

Water Quality

Water quality was not measured because the spring was dry. See Tables 12 and 13 for water quality value ranges from prior years.

Indian Springs Canyon Spring Data Tables

Download All Water Quality Data (Coming Soon)
A small pool of clear water surrounded by boulders and small patches of vegetation
Mouth of the Pecos spring, Amistad National Recreation Area, April 2018

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Recent Findings at Mouth of the Pecos

Mouth of the Pecos was last characterized in WY2018 and was classified as a limnocrene spring (emerges as one or more lentic pools). This spring was a complex of four potential orifices and the water present in April 2018 appeared to be dominated by spring discharge. The spring emerged as a series of pools and flowed into a marshy area. Water flowed from only one orifice into the first pool.

Site Condition

There was slight disturbance from roads/OHV trails and contemporary human. Disturbance from drying was high. Neither crayfish nor bullfrogs were observed.

The crew observed the following obligate/facultative wetland species/genera/families, all of which were also observed during the last visit in WY2019: cattail family (Typhaceae family), fogfruit (Phyla sp.), giant reed (Arundo sp.), mule-fat (Baccharis salicifolia), and willow (Salix sp.)

The crew observed the following invasive plants: giant reed (Arundo donax) in evenly distributed patches; Bermudagrass (Cynodon dactylon) in scattered patches; prickly lettuce (Lactuca serriola) in scattered patches; 1–5 plants of tree tobacco (Nicotiana glauca); and 1–5 plants of sowthistle (Sonchus sp.). This was the first observation of sowthistle at the spring since monitoring began in WY2017. The other species were observed at similar densities in prior years.

A bar graph of water persistence in water years 2017 through 2021. The spring is wet most of the time during that period.
Figure 8. Water persistence at Mouth of the Pecos spring in Amistad National Recreation Area.

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Water Quantity

The WY2021 visit occurred on April 14, 2021. Temperature sensors indicated that Mouth of the Pecos was wetted for 196 of 196 days (100%)—measured up to the WY2021 visit (Figure 8). However, these may be false-positive wetted days as the spring was dry during the WY2021 visit. In prior water years, the spring was also wetted 100% of the days measured. Discharge and wetted extent were not measured because the spring was dry. Tables 14 and 15 show ranges of values for discharge and wetted extent from prior years.

Water Quality

Water quality was not measured because the spring was dry. See Tables 16 and 17 for water quality value ranges from previous years.

Mouth of the Pecos Data Tables

Download All Water Quality Data (Coming Soon)
Article created by the Chihuahuan Desert Inventory and Monitoring Network.

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Amistad National Recreation Area

Last updated: July 18, 2024