What one big straw does to our water.
Every well pulls the water down around it in a funnel, called a cone of depression. Pick how much a new user would pump, then watch the funnel spread through the Carrizo-Wilcox, year by year. The numbers come from the state’s own study of Angelina and Nacogdoches counties.
Try it
| Distance from the well | How far the water drops |
|---|
3D view, 30 miles across. Drag to turn it. The green edge is the Carrizo outcrop to the north, where rain soaks back in. Depth is stretched so you can see it.
Side view, 15 miles each way from the well. The top line is where the water sits now. The red curve is where it would sit.
Change the aquifer numbers
Transmissivity, in gallons a day per foot. The state measured 14,000 to 36,000 for the Carrizo here. Lower means a deeper funnel.
How far north the sand comes up to the surface and refills. The state’s own example used 15 miles. Closer means the funnel levels off sooner.
Storage coefficient. The state used 0.00005 here. Bigger values slow how fast the funnel spreads, but not how deep it ends up.
Does it match what really happened?
Press Industry in 1968 and slide the time to about 30 years. A mile from the well, the model shows the water about 425 feet lower.
The state measured static water levels drawn down “nearly 500 feet near the center of pumping” by 1970, after about 30 years of pumping by the mill and the cities.
That’s close. The real pumping was spread over several well fields and grew over time, so it won’t match exactly. But it shows the math lands in the right neighborhood. [Our reading]
Sources: TWDB Report 110 (1970), abstract and pp. 22–23 (1968 pumping, drawdown near 500 feet); our water history.How it works
In 1970, the state’s consultants figured out how far wells would pull down the Carrizo in Angelina and Nacogdoches counties. They used a standard formula hydrologists have used since the 1930s, called the Theis equation. They treated the outcrop to the north as a line where rain refills the sand. This page runs that same math.
Their own example used a well pumping 500 gallons a minute, a transmissivity of 10,000 gallons a day per foot, a storage coefficient of 0.00005, and an outcrop 15 miles away. We start with those values, except transmissivity. We use 20,000, the middle of the range the state measured for the Carrizo here.
Source: TWDB Report 110, “Coefficients of Transmissibility, Permeability, and Storage” and “Interference Between Wells and Long-Term Drawdowns,” pp. 27–34. Storage coefficients of 0.00007 to 0.0002 for the Carrizo: TWDB Report 327 (1991), p. 13. Power plant request: Powered Land, from Pineywoods GCD records.What this can’t tell you
- It’s one straw in an empty glass. It shows only the new well. Every other well already pumping adds its own funnel on top. The state wrote that these funnels “are additive.”
- It’s not the state’s full groundwater model. The Texas Water Development Board runs a much bigger computer model of the whole aquifer. That’s our next step. Until then, treat these numbers as a fair estimate, not a forecast.
- The sand isn’t the same everywhere. The state measured a wide range. Try the low and high ends under “Change the aquifer numbers.”
- It doesn’t know where any project would put its wells. No data center here has filed for a well permit, and Amp Z’s water use is still listed as “TBD.”
What you can do
The board that permits big wells meets Mon., Nov. 9, at 1:30 p.m. at Kurth Lake Lodge. Bring this page. Ask them how far the water would drop if a big new user moved in, and whether they’ve run the numbers. Here’s how to speak up.