The Third Dimension: Groundwater

By Richard Hazlett

It is ground-water not precipitation that is crucial to our water supplies: and we are over-depleting it and polluting it, often by policy.

I will be speaking about the third dimension of the water picture—what lies unseen as stored water in the earth.

Let’s begin by considering this figure from the Water Replenishment District of Southern California. It shows how the annual precipitation has varied historically at the L.A. Civic Center over the past 130 years, until 2007.The blue bars are the actual annual totals of rainfall measured. Note the tremendous variability. If one were to base water use entirely upon rainfall storage, then a conservative approach would be to restrict water users in Southern California to an expectation of less than 5 inches of rainfall per year; that defines our local environment as a desert. Millions of people would have to leave our landscape.

But the historic average annual rainfall is, in fact, about 15 inches—a bit more than what would climatologically be defined as desert conditions. So, it is more appropriate to refer to the plains of coastal Southern California as an oak-sycamore savannah rather than a desert under natural, pre-settlement conditions. This figure illustrates that, owing to variability, precipitation alone is an insufficient basis as a primary water supply in many parts of the world.

How is it possible, given this pattern, for us to obtain a fairly reliable water supply for a heavily populated region liked ours? We could import the water, as we do with our great aqueducts. But even that water largely comes from areas far north with highly variable precipitation, whether it comes in the form of rainfall or snowmelt. We could build dams to trap surface water, storing and allocating it to provide consistent supply. More often and importantly, we find stable reservoirs of fresh water underground in the form of what we simply call “groundwater.”

If a rain is slow and steady, much of it will seep into the Earth, typically infiltrating at a speed no greater than that of a garden snail moving across a patio. It keeps sinking until the cracks and pore spaces in the ground close up, owing to great pressure deep below.  Then it backfills those cracks and pore spaces, creating an underground body of water, or aquifer, the top of which is a horizon called the water table. The volume of water in the aquifer is controlled on the one hand by its slow outflow to lower elevations, and on the other, by inputs of freshly infiltrated water.

Water may be stored in an aquifer for thousands of years. It is sort of a natural savings account of past infiltration that is freshly replenished in minor seasonal increments. The (rough) average recycling time for groundwater in North American aquifers is 1,400 years. In contrast, all of the water in even the largest surface river will be replaced with fresh supply in less than 20 days at most. So when we pump out groundwater, we are usually pumping out stored supply that takes many human generations to replace.

Therefore, we need to think of our water supply situation as a three dimensional matter. The problem with this is that the state of something which is generally out of sight, as groundwater surely is, is also out of mind—in terms of public perceptions, even of policy and basic accountability practices. Unlike air pollution, for instance, groundwater pollution is something people can easily dismiss---provided the water coming from one’s tap is clean and tastes fresh.

Fresh, clean groundwater is more important for human civilization than fossil fuels, by far. It is the ultimate limiting resource in terms of agriculture and human population. It is the primary drinking water supply for one and a half billion people who could not live without it, including 95% of the rural U.S. population.

And demand is rising, now from industry as well. On average, a ton of water used in industry generates roughly $20,000 worth of output (CPI adjusted 2014 dollars), which is about 70 times as much profit as the same amount of water used to grow grain. At present, about 20% of total aquifer supply is diverted to factories, putting an increasing squeeze on other water uses.

The problem with groundwater is poor global stewardship, complicated by transnational, interstate, and corporate interests. And it can be broken into three overarching categories:

Over-depletion, incentivized by an economic system designed to over-deplete.

Groundwater pollution that results from poor waste storage and management.

And deliberate groundwater pollution to remove the worst liquid wastes from expensive surface storage options.

Let’s consider each category in turn.

As implied by the stats I’ve already provided, we are over-depleting our principle groundwater stocks through well construction and pumping at a rapid and growing rate. Just how serious is the depletion worldwide? We don’t and can’t know for sure. But available data show that this is at least, a big and growing problem. An August 2012 study in Nature by the International Groundwater Resources Assessment Center examined over 700 aquifers of global significance. A map of their data shows degrees of aquifer exploitation “stress” with warmer colors indicating areas of seriously unsustainably overdraft. The areas of most serious concern include the Middle East, northwestern Mexico, and northern India; the latter is the most threatened region in the world in terms of large numbers of people facing long-term water scarcity.

Included in the aquifers of critical concern is the Ogallala, found in the American Midwest, from which almost a third of all U.S. irrigation water comes. At current rates of depletion, University of Kansas hydrologists estimate that this reservoir will be effectively gone in about 50 years.

But depletion alone does not account for shrinkage in useful groundwater supplies. Pollution is another issue.

The problem from wastes leaking unintentionally into the ground is enormous. And it isn’t just human beings who are to blame. In the United States, farm animals produce 130 times as much waste as humans do, with millions of tons of pig and cattle feces washing into streams and rivers every year. Much of the nitrogen they carry ends up in groundwater, together with nitrates from fertilizers and various pesticides and herbicides.

Consumed in high concentrations of above 10 mg per liter of water, nitrate contamination can cause methemoglobenemia, a condition that can kill babies. If levels are above 100 mg per liter, according to the EPA, then this condition is highly likely. In the US, the Geological Survey reports that about 15% of our groundwater supplies exceed safe standards for nitrates. In China, monitors report drinking well water nitrate concentrations of as high as 300 milligrams per liter!

Even more impactful are carcinogenic petroleum products in groundwater, seeping in from old, rusting, leaky gas tanks beneath service stations and motor pools. In Texas alone, over 90% of counties report leaky gas tanks which, according to the EPA, has affected, or has the potential to affect, virtually every major and minor aquifer in the state.

Then, there are the deliberate additions of pollutants to groundwater. In the United States this has been done both as a matter of perceived need for national security, and as ordinary waste disposal policy.

The Hanford site in Washington State, where plutonium was manufactured to make atomic bombs during the Cold War, lies astride the Columbia River. As a byproduct of plutonium production, engineers intentionally dumped 450 billion gallons of radioactive liquid wastes into the ground, creating eight plumes of radioactive groundwater that are working their way to the riverbank much faster than expected. In fact, the engineers thought that it might take as long as 10,000 years for any contaminants to reach the local water table—an example of greatly oversimplified groundwater modelling.

Without action, the Columbia River will surely become radioactive as it flows past Portland, Oregon. But when? The Oregon Department of Energy states, “We don’t know when this will occur, or how much waste will leak or in what concentrations it will reach the river.” To deal with the problem, the government is committing more than $150 billion dollars on the largest environmental clean-up operation in the world. It is not progressing very well, I must say.

Even more general surprising for ordinary citizens, I think, is the deliberate policy of injecting vast amounts of chemical wastes from industry, and some municipal wastes in the form of raw sewage, deep into American groundwaters. The idea is to place it underground where aquifers are stagnant, and capped by impermeable rock layers, called aquicludes. This quarantines the pollution more or less geologically. And, if this isn’t possible, then the waste can be injected into aquifers that are not being used—presently anyhow—for drinking purposes.

Over 680,000 wells have been drilled in the United States to legally dispose of hazardous wastes. Nine billion gallons of toxic fluids go down the hole each year. The underground sacrifice zones underlie broad swaths of America—especially in the Midwest. Why not just store these toxins in secure landfills at the surface? Because landfilling would be too expensive to industry and city governments, and because too few landfills exist to accommodate the waste, with intense political pressure exerted to keep it that way. Not in My Backyard, please!

Added to this dangerous injection stream, too, are the toxic wastes used in hydrofracking—the source of the new American gas and oil boom, which are largely reinjected into the crust after use. These contain god knows what in terms of constituents. The ingredients are largely proprietary secrets, owing to business pressure on Congress and state governments, but because they impact a public resource – water – we should know what they consist of. We do know that they include such substances as formaldehyde and the ingredients that go into shampoo—and that they have a serious impact on ecosystems if spilled at the surface.

We also know that this stuff, irrespective of intention, is filtering into well-used public aquifers in many places. The reason is that we have no way of completely understanding the structure that governs groundwater flow, except in a theoretical sense. USGS hydrologist J.D. Bredehoeft stated tellingly that no groundwater model we have ever created is unflawed, quite often in critical ways.

Why then do we deliberately inject this stuff? Of course it is a powerful combination of economic and political expedience coupled with profound technical ignorance and short-term convenience.

What must we do? I’ll give Payal Sampat, a Worldwatch Institute researcher, almost the last word:

In many places, various authorities and industries have fought back the contamination leak by leak, or chemical by chemical, only to find that the individual fixes don’t add up. As we line landfills to reduce leakage, for instance, tons of pesticide may be running off nearby farms and into aquifers. As we mend holes in underground gas tanks, acid from mines may be seeping into groundwater unchecked. Clearly it’s essential to control the damage we’ve already inflicted, and to protect communities and ecosystems from the poisoned fallout. But given what we already know, that damage to aquifers is mostly irreversible, that it can take years before groundwater pollution reveals itself, that chemicals react synergistically, and often in unanticipated ways, it’s now clear that a patchwork response isn’t going to be effective. Given how much damage this pollution inflicts on public health, the environment, and the economy once it gets into the water, it’s critical that the emphasis be shifted from filtering out toxins to not using them in the first place.1

The final word goes to Andrew Skinner, head of the International Association of Hydrogeologists, who puts it this way: “Prevention is the only credible strategy.”

 

 

1Payal Sampat, “Groundwater Shock: The Polluting of the World’s Freshwater Supplies,” Worldwatch Magazine, 13:1, January/February 2000, http://www.worldwatch.org/node/481. 

 

© Richard Hazlett, 2014