Lowest Groundwater Level Recorded Since 2005
April 2021 Hydro Report
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Groundwater, springs, creeks, and rivers are connected in the Hill Country. In March, groundwater levels in the HTGCD Mt. Baldy monitor well, a Middle Trinity Aquifer (Cow Creek) well, reached the lowest level recorded since Nov. 2005 (Fig. 1). Most of Western Hays County residents rely on either wells or groundwater-supplied water utilities. Many groundwater conservation districts (see table below for specifics) have declared drought and are enforcing pumpage curtailments to extend water supplies until rainfall can replenish groundwater supplies.
Typically, fall and winter rains generate recharge to replenish groundwater supplies–but the series of small rainfall events during this year’s wet season didn’t create much runoff, and therefore, not much recharge reached our aquifers (Fig. 2). The exceptionally low water levels in monitor wells reinforces the importance of water conservation while drought conditions persist.
In the Hill Country, spring flow and streamflow are good indicators of groundwater conditions. Figure 3 shows a hydrograph of baseflow provided by Middle Trinity Aquifer springs in the Blanco River and Cypress Creek correlated with rainfall totals. As water levels in the aquifer decline, spring flow decreases.
In many ways, we are in the middle of a sneaky drought. Small rain events have supplied enough water to support surface vegetation, but they haven’t generated enough runoff to recharge area aquifers. With these dry conditions, rainfall is absorbed by exceptionally dry soils. After the prolonged dry conditions, it will take several consecutive rains to wet the soils before sustained recharge can refill the aquifers.
On March 23, the EAA weather station near Burnett Ranches measured 0.76 inches and a private weather station in downtown Wimberley measured 0.93 inches of rain. Given dry soils, this welcome rainfall did little to replenish groundwater supplies. In western Hays County, baseflow conditions at the Blanco River and Cypress Creek have seen steady declines throughout the fall and winter.
Such low spring flow is an exceptionally troubling condition; however, watching the flow trends for Middle Trinity springs and taking action as key thresholds are crossed mean we as a community can slow groundwater decline and extend supplies. Springs are a key indicator of groundwater storage and the status of our groundwater supply.
Water conservation now will help extend water resources and protect habitat until enough rain events generate meaningful recharge. Take a moment to tune up your well and clean your pump house and fix pesky drips and leaks. Be part of the collective solution to protect our shared water supply.
Groundwater Drought Declarations
No matter what area agencies call their drought declaration, it’s obvious water levels and spring flows have declined to exceptionally low levels. In order to preserve groundwater availability, coordinated water conservation measures are essential.
Agency | Drought Stage | Date Declared | Details |
Hays Trinity GCD | Jacob’s Well GMZ – 30% Curtailment Remaining GCD – 20% Curtailment |
Nov. 2020 | Board Order, 11/1/2020 |
Barton Springs Edwards Aquifer CD | Stage II Alarm Drought (20% Curtailment or more) | Oct. 2020 | Press Release, 10/9/2020 |
Edwards Aquifer Authority | San Antonio Pool is in Stage 1 – 20% Reduction | Apr. 2021 | Press Release |
[Updated 4/1/2021]
Annual rainfall average for Central Texas is approximately 33 inches per year. To understand recharge potential, it’s important to track where rain falls, how fast it falls, and how saturated the soils are. Key rain gages for the area are (upstream to downstream):
Realtime comparison of two key spring flow sites: (USGS gages: Blanco at Fischer Store–08170950 and Jacob’s Well–08170990)
Jacob’s Well Spring, Cypress Creek
Jacob’s Well is a Middle Trinity Aquifer spring that provides the baseflow for Cypress Creek.
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- Realtime data: USGS 08170990 Jacobs Well Spg nr Wimberley, TX
- Spring flow is a strong indicator of groundwater levels in the Jacob’s Well Groundwater Management Zone (JW GMZ), because low spring flow directly correlates to low well water levels.
- The 10-day average spring flow is a drought trigger for the HTGCD Jacob’s Well GMZ (Thresholds: 10% Curtailment: below 6 cfs; 20% Curtailment: below 5 cfs; 30% Curtailment: below 3 cfs).
- Groundwater pumping causes 1 to 1.5 cfs fluctuation in flow and is more evident under low flow conditions.
Pleasant Valley and Park Spring, Blanco River
Pleasant Valley and Park Springs are Middle Trinity Aquifer springs that provide significant baseflow for the Blanco River, especially during dry periods.
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- Realtime data: USGS 08170950 Blanco Rv at Fischer Store Rd nr Fischer, TX
- Springflow can be estimated by using the USGS gage at Fischer Store Rd (linked above) and subtracting any upstream flow indicated by the USGS 08170905 Blanco Rv at Valley View Rd nr Fischer, TX.
- These springs are central to the HTGCD Regional Recharge Study Area, because springflow is indicative of water storage in the local groundwater system.
The Hill Country’s iconic streams are known for their clear water and rocky bottoms. Oftentimes, cracks, caves, and faults are visible in stream beds. When creeks and rivers are flowing, these cracks, caves, and faults channel water from the surface into the groundwater system below. Streamflow gages are strategically located to help monitor gaining (where springs are found) and losing (where recharge happens) sections of creeks and rivers. Key gages include:
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- Realtime data: USGS 08170950 Blanco Rv at Fischer Store Rd nr Fischer, TX
- Springflow can be estimated by using the USGS gage at Fischer Store Rd (linked above) and subtracting any upstream flow indicated by the USGS 08170905 Blanco Rv at Valley View Rd nr Fischer, TX.
- Realtime data comparison of three key USGS gages (Blanco at Fischer Store–08170950, Jacob’s Well–08170990, Blanco at Wimberley–08171000)
Groundwater monitoring is an art. TWDB, HTGCD, and BSEACD have extensive monitoring networks.
Key wells from west to east:
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- HTGCD Burnett Ranch well (aka ESD well) – Middle Trinity aquifer
- HTGCD Mt Baldy well – Middle Trinity aquifer
- HTGCD Downing well – Middle Trinity aquifer
- BSEACD Hoskins well – Edwards aquifer
- BSEACD Lovelady well – Edwards aquifer
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- USGS Texas Water Dashboard
- LCRA Hydromet
- TWDB Recorder Wells
- EAA Rainfall Monitoring Network
- BSEACD Monitoring Sites
- The Nature Conservancy
- TCEQ Source Water Quality Monitoring (SWQM) Data Viewer
- Texas Stream Team/Cypress Creek Project
Archived Hydro Reports
Month | Cypress Creek – Jacob’s Well | Blanco River – Pleasant Valley & Park Springs | Date Published |
2021 March | 2.4 cfs | 13.5 cfs | 3/10/2021 |
2021 January | 0.3 cfs | 11.8 cfs | 1/19/2021 |
2020 December | 1.3 cfs | 16.8 cfs | 12/8/2020 |
2020 November | 1.1 cfs | 17.1 cfs | 11/11/2020 |
2020 October | 1.7 cfs | 17.7 cfs | 10/25/2020 |
2020 September | 6.5 cfs | 25.2 cfs | 9/14/2020 |
Please note: Page under construction. Please email robingary@wimberleywatershed.org with suggestions or questions.