Another Storm Brewing: The Groundwater Debate and How It Relates to Flood Risk

Groundwater relates to flooding? Yes. Here’s how. And here’s why you should care, especially now.

In November, Montgomery County voters will elect board members to the Lone Star Groundwater Conservation District who may advocate using more groundwater, a move that some believe could give residents cheaper water in the short run, but which could also cause subsidence, contribute to flooding, create shortages, raise costs and limit growth in the long run.

Unequal Groundwater Withdrawals, Unequal Subsidence

Subsidence is scientifically well documented and understood. Removing groundwater from clay causes the clay to compress. When that happens, you sink. And once clay is compressed, it stays compressed forever – even when rehydrated.

Yet some Montgomery County voters are advocating removing more groundwater because, at this moment, it’s cheaper than surface water. They are betting their future and their neighbors’ futures on it.

Subsidence can contribute to flooding because not everybody subsides equally. While Kingwood only subsided two feet in the last century, one part of Baytown subsided so much that it became uninhabitable in about half that time.

In 1944, the area that would become Brownwood in Baytown was starting to show signs of development.

By 1978, Brownwood was well developed…and sinking fast.

Today, the area floods so much that it is uninhabitable. All the homes are gone. Brownwood has been turned into a park.

The “Pump-Now, Let-Somebody-Else-Pay-Later” Mentality

Subsidence generally happens so slowly that some people claim it’s not a problem. Especially those on higher ground. They want to continue to pump water from their wells because they perceive it to be cheaper than surface water. It can be…at least in the short run..until wells run low or dry. Then pumping costs increase…often along with salinity…and the people who depend on the well are out of water and out of luck.

Gulf Coast Aquifers: Source Harris-Galveston Subsidence District. Much of the water in Montgomery County used for human consumption is pumped from the Jasper aquifer.

Depleting at More Than 500X the Recharge Rate

Still, some people say, “I’ll worry about that when it happens.” Problem is:

The rate of depletion will exceed the rate of recharge by more than 500X.

More Expensive in Long Run

Now consider this. As pressure in an aquifer decreases, the cost of bringing water to the surface increases dramatically, sometimes to the point where recovery is no longer economical, i.e., competitive with surface water. It’s much like the oil industry. As a rule of thumb, half the oil in reservoirs is left in the ground because it’s too expensive to recover.

For all these reasons, most counties in the region are trying to switch people to surface water. Their groundwater withdrawals have either declined or stayed the same.

Counties surrounding Montgomery have either decreased groundwater pumping or kept it constant.

Meanwhile, Montgomery County’s groundwater withdrawals have soared.

Montgomery County groundwater pumping, however, has generally increased in the last three decades.

A report by LBG Guyton Associates to the Lone Star Groundwater Conservation District showed that the largest increase in pumping since 2000 has occurred in Montgomery County. Pumping in surrounding counties has generally decreased since 2000.

Montgomery County Growth

The surge in Montgomery County groundwater usage is largely because Montgomery County has grown so quickly. With the exception of Fort Bend County, Montgomery County is growing faster than any county in the region on a percentage basis.

Houston Region growth last year by county. In percentage terms, Montgomery County trailed only Fort Bend County. 

So Why Worry NOW?

Water resources take so long to develop that they need to be planned 50 years into the future. The Houston region’s population tripled in the last 50 years.

If Montgomery County expects to grow that fast in the next 50, where will the water come from to support that growth? Especially if voters undermine the financial viability of the half-billion dollar surface-water treatment plant – that they just built – by shifting to groundwater!

Proponents of unlimited groundwater pumping in Montgomery County will ELECT directors of the Lone Star Groundwater Conservation District for the first time in November.

If people vote for candidates who advocate use of “cheaper” groundwater in the short term, they will also be voting for subsidence and policies that limit long-term growth. Without question, they will be betting their future on a rapidly depleting water source.

If that’s the will of the people, so be it. I just hope they don’t set a precedent that residents in neighboring counties follow. If so, we could all be sunk.

Red contours show subsidence in the last century. Blue contours show how much subsidence has increased in the first sixteen years of this century. Note the widening gap between red and blue at the top of the frame. It shows that subsidence in Montgomery and northern Harris Counties is increasing at an increasing rate. Parts of Harris County have subsided 10 feet! Source: Harris-Galveston Subsidence District.

Posted 9/14/2018 by Bob Rehak

382 Days since Hurricane Harvey

Note: Because this is such an important issue, I have created a new tab titled Subsidence on the Reports page.