Northern Trinity / Woodbine:

Transcription

1 Northern Trinity / Woodbine: Historical Use and Projected Impacts R. W. Harden & Associates, Inc. Hydrologists Geologists Engineers

2 Study Area

3 Study Area

4 Geology / Hydrostratigraphy System Series Groups Formation Approximate Maximum Thickness North South North South Tertiary Undifferentiated Navarro Taylor ,100 Gulfian Austin Undifferentiated Undifferentiated Eagle Ford Woodbine Washita Grayson Marl Mainstreet, Pawpaw, Weno, Denton Fort Worth, Duck Creek Buda, Del Rio Georgetown 700 1, Kiamichi Kiamichi 50 Cretaceous Edwards 175 Goodland Fredricksburg Comanche Peak Comachian Walnut Clay Walnut Clay 200 Paluxy Paluxy Glen Rose Glen Rose 1,500 1,500 Hensell Hensell Trinity Antlers Cow Creek Twin Mountains Travis Peak Pearsall Hammett Sligo 1,000 1,800 Hosston Hosston Paleozoic Undifferentiated Model Layers GHB

5 Conceptual Flow - Predevelopment

6 Eureka! "Ring the bells and sound the tom-tom. Waco leads the rest of the state in artesian wells--a well that will supply the city with pure freestone water." "At two o'clock, in the afternoon, while the auger, which has been drilling for two months on Bell's Hill, in J. D. Bell's artesian well struck a white sand strata and a great subterranean ocean of water at the same time." "From a 5 and 5/8 in. pipe this morning a river is running over Bell's Hill, with an estimated flow of four hundred thousand gallons daily. The contractors estimated that the force of water is sufficient to raise the water in a stand pipe to a height [sic] of one hundred, and perhaps, one hundred and twenty-five feet." Waco Evening News, March 12, 1889

7 Geyser City...Waco advertised itself as a "Geyser City" and built several natatoriums urging visitors to drink and bathe in its 104 degree [F] water in order to cure "dyspepsia, rheumatism, syphilis, eczema, many other chronic problems. Scenes in and near Waco [Walker, 1983]

8 Pure and Infinite Water! "boundless flow "a value inestimable "immense body of water "incalculable "inexhaustible quantities" Waco Evening News, March 12, 1889

9 OOPS! "The people of Waco thought the supply of artesian water was certainly inexhaustible, but in 1894 the wells began to produce less water and even go dry*." Walker [1983] *(cease to flow at the surface)

10 Conceptual Flow Post-Development

11 Trinity/Woodbine GAM A tool for estimating likely aquifer responses to hydrologic stresses (pumpage, drought, etc.) Two years in the making Completed in October 2004

12 What a Regional GAM Can and Can t Do CAN DO Provide estimates of regional water level changes under different use scenarios (amounts and distributions) Provide estimates of the relative importance of different aquifer flow components (recharge, leakage, etc.) under different aquifer stages CAN T DO Determine the amount of water that should be produced Determine policy or an appropriate management strategy

13 System Subdivision - Model Grid

14 Model Diagram

15 Applied Recharge vs. Accepted Recharge Estimated Recharge Rate ET Abstracted from Model (Variable with Water Levels) ET Simulates: Evaporation Transpiration Springs Seeps Baseflow to Streams Recharge Accepted into Downdip Aquifer (Recharge ET)

16 Model Water Budget ( )

17 Predictive Simulations Pumpage from Regional Water Planning Groups and TWDB (GAM predictive) 2. Current pumpage held constant (2000 to 2050)

18 GAM Predictive Pumpage

19 Simulated and Measured Water Levels (1880 to 2050) Waco Region

20 Woodbine Hill County Water Level Elevation (Feet MSL) Simulated Constant Pumpage Simulated - GAM Predictive Pumpage Measured Water Level Top of Aquifer Base of Aquifer Year

21 Paluxy Hill County Water Level Elevation (Feet MSL) Simulated Constant Pumpage Simulated - GAM Predictive Pumpage Measured Water Level Top of Aquifer Base of Aquifer Year

22 Hensell Mclennan County Water Level Elevation (Feet MSL) Simulated Constant Pumpage Simulated - GAM Predictive Pumpage Measured Water Level Top of Aquifer Base of Aquifer Year

23 Hosston Mclennan County Water Level Elevation (Feet MSL) Simulated Constant Pumpage Simulated - GAM Predictive Pumpage Measured Water Level Top of Aquifer Base of Aquifer Year

24 Simulated and Measured Water Levels (1880 to 2050) Dallas Fort Worth Region

25 Paluxy Tarrant County Water Level Elevation (Feet MSL) Simulated Constant Pumpage Simulated - GAM Predictive Pumpage Measured Water Level Top of Aquifer Base of Aquifer Year

26 Twin Mountains Tarrant County Water Level Elevation (Feet MSL) Simulated Constant Pumpage Simulated - GAM Predictive Pumpage Measured Water Level Top of Aquifer Base of Aquifer Year

27 Twin Mountains Tarrant County Water Level Elevation (Feet MSL) Simulated Constant Pumpage Simulated - GAM Predictive Pumpage Measured Water Level Top of Aquifer Base of Aquifer Year

28 Conclusions Large historical water level decline rates resulted from increases in historical rates of pumpage Continuation of current pumpage will likely result in decreased decline rates Current rates of pumpage are probably sustainable for many decades

29 Conclusions Cont. The Trinity/Woodbine is relatively drought resistant Local conditions may vary!

30 Northern Trinity / Woodbine Aquifer System R. W. Harden & Associates, Inc. Hydrologists Geologists Engineers

31 The Trinity/Woodbine Aquifer System: Historical Use and Projected Impacts James Bené, P.G. - Session B: Management Applications: North/West Texas Aquifers - Room: E2.002 Abstract Covering over 30,000 square miles, the Trinity/Woodbine is one of the most extensive sources of groundwater in Texas. Although they are not always distinguishable from one another in geologic section, the four primary aquifers that comprise the system (Hosston, Hensell, Paluxy, and Woodbine) extend from southwestern Arkansas to the Colorado River in Central Texas. The northern portion of the aquifer system has supplied the vast majority of groundwater to all or part of 55 counties in the region for more than a century. Extensive development of the Trinity aquifer began in the late 1800 s when numerous, artesian, flowing wells were completed in the Trinity throughout central and northern Texas. The practice of leaving flowing artesian Trinity/Woodbine wells uncapped combined with the newfound availability of fresh water led to regional artesian pressure declines, and many wells ceased flowing by the early 1900 s. Because of this, an interval of reduced groundwater production in the Trinity/Woodbine was experienced in the region through the 1930 s. This period was followed by many decades of increased groundwater withdrawal in many areas of Central and North-Central Texas to meet the local water demands of a growing Texas population. Because the Trinity/Woodbine is structurally complex and encompasses a relatively large area, the long-term aquifer response associated with groundwater use is not always readily apparent. For this reason, construction of the Northern Trinity/Woodbine Groundwater Availability Model (GAM) was necessary in order to assist in quantifying the effects related to the ongoing development of aquifer resources in the region. Following construction and verification of the model, several simulations of aquifer response to projected groundwater demands (as developed by the TWDB and applicable Regional Water Planning Groups) were performed. In general, the results of these simulations indicate that water levels will remain relatively stable in outcrop zones, while artesian pressures will rise by several hundred feet in the major pumping centers in response to a planned decrease in pumpage from these aquifer units over the next 50 years. In simulations where current pumpage rates are held constant in the future, the model results indicate that artesian pressure levels will continue to decline, but at a much lesser rate than was recorded during the last century. The GAM results also suggest that the Trinity/Woodbine system is relatively stable and largely insensitive to changes in near-surface fluxes such as recharge and surface/groundwater interaction. This assessment is corroborated by the lack of coherent, historical water table declines in Trinity/Woodbine outcrop areas despite fluctuations in precipitation and widespread, sustained pumpage throughout the last 50 years.