Last updated: September 19, 2024
Article
Climate and Water Monitoring at Lyndon B. Johnson National Historical Park: Water Year 2023
NPS/CYNTHIA DORMINEY
Overview
Together, climate and hydrology shape ecosystems and the services they provide, particularly in arid and semi-arid ecosystems (Woodhouse and Overpeck 1998). Understanding changes in climate, groundwater, and surface water is key to assessing the condition of park natural resources—and often, cultural resources.
At Lyndon B. Johnson National Historical Park (Figure 1), Southern Plains 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 problems, allowing managers to mitigate them before they become worse. At Lyndon B. Johnson National Historical Park, we monitor climate and groundwater, among other vital signs.
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., WY2023 runs from October 2022 through September 2023). This article reports the results of climate and groundwater monitoring at Lyndon B. Johnson National Historical Park (Figure 1) in WY2023.
Reference: Woodhouse, C. A., and J. T. Overpeck. 1998. 2000 years of drought variability in the central United States. Bulletin of the American Meteorological Society 79(12): 2693–2714. https://doi.org/10.1175/1520-0477(1998)079%3C2693:YODVIT%3E2.0.CO;2
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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
A National Oceanic and Atmospheric Administration Cooperative Observer Program (NOAA COOP) weather station (Johnson City 2N 414605) has been operational near Lyndon B. Johnson National Historical Park since 1964 (Figure 1). This station typically 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.
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Results for Water Year 2023
Precipitation
Annual precipitation near Lyndon B. Johnson National Historical Park in WY2023 was 18.43″ (46.8 cm), 14.59″ (37.1 cm) less than the 1991–2020 annual average. Monthly precipitation in WY2023 was less than the 1991–2020 averages, except in November and May (Figure 2). Less than a quarter of the monthly average precipitation occurred in October, December, March, July, and August. Extreme daily rainfall events (≥ 1″; 2.54 cm) occurred on 3 days, substantially less the average annual frequency of 9.9 days. Extreme rainfall events occurred on 24 January 2023 (1.05″; 2.7 cm), 11 May 2023 (1.83″; 4.6 cm), and 24 May 2023 (1.18″; 3.0 cm).
Air Temperature
The mean annual maximum temperature near Lyndon B. Johnson National Historical Park in WY2023 was 83.1°F (28.4°C), 3.2°F (1.8°C) above the 1991–2020 average. The mean annual minimum temperature in WY2023 was 55.8°F (13.2°C), 1.8°F (1.0°C) above the 1991–2020 average. Mean monthly maximum and minimum temperatures in WY2023 differed by as much as 8.4°F (4.6°C; see August as an example) relative to the 1991–2020 monthly averages (Figure 2). Mean monthly maximum and minimum temperatures were warmer than the 1991–2020 averages for most of the year. Summer (June–September) temperatures were notably warmer. Extremely hot temperatures (≥ 99°F; 37.2°C) occurred on 85 days in WY2023, over three times the average frequency of 24 days. Extremely cold temperatures (≤ 27°F; −2.8°C) occurred on 19 days, similar to the average frequency of 20.2 days.
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Drought
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 index for Lyndon B. Johnson National Historical Park indicates that WY2023 was drier than the 1991–2023 average from the perspective of both precipitation and potential evapotranspiration (Figure 3).
Reference: Tsakiris G., and H. Vangelis. 2005. Establishing a drought index incorporating evapotranspiration. European Water 9: 3–11.
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Groundwater
Groundwater is one of the most critical natural resources of the Southern Plains and American Southwest, providing drinking water, irrigating crops, and sustaining rivers, streams, and springs throughout the region.
Methods
Lyndon B. Johnson National Historical Park groundwater is monitored at two wells outside the park (Figure 1) by the Texas Water Development Board (TWDB). Well 57-51-317 is
1 mile (1.61 km) west of the LBJ Ranch District and is monitored twice a year. Well 57-45-822 is adjacent to the western edge of the Johnson City District and was monitored manually through WY2022. Starting in November 2022 (one month into WY2023), we began monitoring the well daily using automated methods. Data are available at the TWDB Database.
Results for Water Year 2023
Average depth to water at well 57-45-822 in WY2023 was 59.09 feet below ground surface (ft bgs; 18.01 m bgs), lower than the previous year (Table 1). In September 2023, the water level reached 63.57 ft bgs (19.38 m bgs), the lowest in the monitoring record. Average depth to water at well 57-51-317 in WY2023 was 29.95 ft bgs (9.13 m bgs), lower than the previous water year. Well 57-45-822 shows substantial seasonal variation, likely in response to precipitation and associated shallow recharge (Figure 4). Well 57-51-317 does not exhibit high inter-year variability, likely because it is situated 500 ft (152 m) from the Pedernales River. The monitoring data indicate that water level in both wells is declining over their respective periods of record.
Table 1. Groundwater monitoring results in water year 2023 (WY2023), Lyndon B. Johnson National Historical Park (amsl = above mean sea level; bgs = below ground surface).
| State Well Number | Location | Wellhead Elevation (ft) |
Depth to Water (ft bgs) |
Water Level Elevation (ft amsl) |
Change in Elevation from WY2022 (± ft) |
Change in Elevation from Earliest Recorded Water Level (± ft and year of first record) |
|---|---|---|---|---|---|---|
| 57-45-822 | 14 ft west of the Johnson City District | 1,233 | 59.09 | 1,173.91 | −8.04 | −23.57 (2004) |
| 57-51-317 | 1 mile west of LBJ Ranch District | 1,447 | 29.95 | 1,417.05 | −0.90 | −3.50 (2016) |
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Authors: Kara Raymond, Andy Ray
Please cite this report as
Raymond, K., and A. Ray. 2024. Climate and Water Monitoring at Lyndon B. Johnson National Historical Park: Water Year 2023. Southern Plains Network, National Park Service, Pecos, New Mexico.
Please cite this report as
Raymond, K., and A. Ray. 2024. Climate and Water Monitoring at Lyndon B. Johnson National Historical Park: Water Year 2023. Southern Plains Network, National Park Service, Pecos, New Mexico.