Refilling Our Wells

by GRANT CANNON

1

ON the giant King Ranch which stretches over the arid Gulf plain of Texas, the Klebergs, who own the ranch, have built a 1500-acre lake with the intention of pouring the water down a rathole. Near the dam that holds this vast pond, they have drilled a deep well. The water from the lake is piped to the well, filtered to remove silt, and pumped down the well to spread through the waterbearing sands deep in the earth. Here the water is held without evaporation and moves under the million acres of the ranch to replenish the hundreds of windmills that pump water for the livestock.

Since the dam was built, they have collected only enough water for one such effort to recharge the underground aquifer or reservoir. Though the pressure of the windmill wells for miles around seemed to have been built up slightly by this first try, the Klebergs arc not yet ready to claim even a limited victory over the drought. They do know, however, that in other parts of t he count ry methods such as this have helped save some of the vast amount of precious water that flows from the land where it is needed into the sea.

Just how precious water is may be summed up in a few figures. We are now using around 17.3 billion gallons of water a day — four times as much as we did fifty years ago when our population was only half as large. In another twenty-five years, hydrologists estimate, we will be using twice as much water as we do today. If the hydrologists are right — and these students of our water problems tend to be conservative — water will probably be the most important single factor in determining the location as well as the future growth of industry.

Of our total water supply, underground water sources offer the greatest opportunity for exploitation and development:. In some sections of the country these reservoirs are not used to the extent that they might be. In other areas their use could be increased by artificially recharging them during those seasons when our surface water supply is so abundant that it creates a problem in drainage or a threat of flood. Essentially these aquifers are great rock sponges — beds of sand or gravel or other rock material which is porous enough to permit water to flow through it. They generally lie parallel to the earth’s surface or on a slight downward slope. They may be covered partly or almost entirely by layers of clay or shale which do not permit the surface water to reach them, but usually there is an area where the surface water can percolate down to the aquifer and then flow laterally to a point of discharge such as a spring, a river, a gully, or the ocean. When water flows through a downward-sloping aquifer which is topped by an impervious layer, as at the King Ranch, considerable pressure is built up; and when this roof is punctured by a well the water will flow up above the aquifer and may shoot, up several feet above the land surface as a flowing well.

In the great natural water cycle — the evaporation of the water from the sea, its wind-blown movement over the land and the fall upon the land either as rain or snow, and its passage back to the sea as runoff or into the air through evaporation — in this eternal giving and taking away, the aquifer acts as a stabilizer. Where the surface water rushes down the streams into the rivers and on to the sea or into a lake or pond whore evaporation takes place, the ground water percolates slowly into the; aquifer and inches its way through the porous material to an outlet. These outlets in the inferior of the country supply our rivers and streams with a great part of their water and keep them running during times of little rain.

The way in which water enters an aquifer and flows through it is of great importance to hydrologists in formulating plans for better water use and in making recommendations for water laws. They have learned that even in areas where water can percolate down into the aquifer, the topsoil has first right to the rain or melted snow. Only when this upper layer of soil is fully saturated is water available to seep down and recharge the aquifer below.

The rate of flow of the water through the aquifer is another problem which is being given study. The size of the aquifer, the materials which compose it, and the amount of pumping from it all influence its rate of flow. In the northern Great Plains, for example, parts of the Dakolas, Minnesota, and Iowa are underlain by one of the most extensive water-bearing formations in this country — the Dakota sandstone aquifer. In some places the water travels through this great slab for a distance of 300 miles between the natural recharge area in the Rocky Mountain foothills and the wells in Iowa. When wells were first drilled through the shale cap some seventy years ago, the pressure was so great that the flowing water was used to power water wheels. With thousands of wells tapping this great source — there are a reported 10,000 in North Dakota alone — the flow has steadily decreased. When the first wells were sunk the pressure was sufficient to raise the water anywhere from 200 to 400 feet above the surface: today those wells which still flow produce but 3 or 4 gallons a minute, and in most places water must be pumped from the aquifer.

The slow movement, of the water in the aquifer is responsible for a curious phenomenon. As the water is pumped up through the screened end of a deep well pipe, it is pulled up the pipe faster than it can flow through the porous material, and immediately around the pipe the water table falls or, if you can think only of the liquid in the aquifer, a dent is formed in it. As this waterless dent is deepened it forms a cone — called a cone of depression by hydrologists — which in turn creates a downgrade for all the water around it so that its flow through the aquifer is quickened. A group of wells in a municipal or industrial well field will create a composite cone of depression.

This downward cone within the aquifer has caused one of our major problems in underground wafer storage. When overpumping lakes place in Illinois, or New Mexico, or any of the inland parts of the country, the water table drops until the cost of pumping is so great that the well is abandoned either permanently or until the aquifer is refilled. When such a cone of depression is created near the coast, however, sea water may be drawn into the porous material, contaminating the remaining fresh water and ruining the aquifer itself with salt deposits.

So far there has been no sea-water contamination of the water on the King Ranch. This is a danger, however, since the cone of depression caused by pumping at Kingsville and on the ranch brings a flow of water from the Gulf of Mexico side of the aquifer as well as from the west. Logs kept by the well drillers who have punched down hundreds of water and oil wells in this area have given the geologists a good picture of the water-bearing formations that lie beneath the surface. The shallowest are mere sand-filled pockets which hold the rain. Relow these pockets, about a hundred feet from the surface, is a shallow fresh-water stratum underlain by a salt-water aquifer believed to have once been a salt-water lake which was filled with sand and gravel over the centuries. The most important aquifer —the one the Klebergs are trying to recharge from their lake — is a layer of sand from 10 to 150 feet thick lying from 400 to 700 feet beneath the surface. It is a great strip some 30 miles wide which runs east from its natural recharge area to the edge of the continental shelf in the Gulf of Mexico. The water flows through this layer of sand at the rate of 3 million gallons a day, but when the F.S. Geological Survey measured it in 1934, it was being pumped out at better than 4 million gallons a day. The usage rate is probably considerably higher today.

2

THE effort to make up this deficit by catching the surface water and recharging the aquifer artificially through a well was cosily and daring. It must have been an enormous templnlion during the blislering dry summer of 1953 to pipe the lake water to the ranch headquarters and the watering troughs inslead of risking losing it in the sands below. But the advantages of underground storage, if the gamble works, are enormous. Not a penny need be spent on extra pipe, for the water will flow through the sand to the windmills which pump it directly into the watering tanks. An even greater advantage is that where the lake would lose thousands of gallons of water each day from evaporation, the sun will not draw a drop of water directly from the aquifer. True, the city of Kingsville will pump some of this recharge water into its water system before the windmills can draw it out for the ranch; but Kingsville would be drawing water out. from beneath the ranch whether the klebergs recharged or not.

An example of how permanently water can be held in some aquifers can be seen at Fessenden, North Dakota. This town of less than 1000 population has drawn its water from three lens-shaped gravel aquifers which are not known to have either recharge areas or natural outlets. Geologists believe that the sand and gravel and the water itself may have been left there by the receding glacier thousands of years ago and remained pure and fresh until tapped at the turn of the century. One of these lenses supplied the town with water for twenty years before the other two were discovered to supplement the dwindling supply. These aquifers were eventually pumped dry, and the village hauled its water until it found the shallow aquifer that is being pumped at the present time. The old, depleted aquifers could now be recharged on a longterm basis. They offer a unique opportunity for permanent storage to fill future needs.

In the country as a whole, underground sources provide us with around 15 to 20 per cent of our total water for irrigation and for industrial, municipal, and domestic use. But the demand for water from this source is increasing even faster than the demand for surface water. It is generally cooler, purer— that is, freer from bacterial contamination — and more uniform in temperature and chemical quality than surface water. These are qualities which make ground water particularly desirable for industrial purposes. And industry is iar and away the heaviest user of water. It takes, for example, 65,000 gallons of water to produce a ton of steel (and America now produces around 100 million tons a year) and 40,000 gallons to make a ton of wood pulp for paper. Each automobile that comes off the assembly line represents over 100,000 gallons of water used, and 20 more gallons are required for the refining of a gallon of oil to make gasoline and lubricant to run it. The importance of low-temperature ground water is emphasized by the fact that 75 per cent of all water used in industry is needed for cooling or in exchange for heat.

When industry uses water, it returns most of it to our streams — along with a pollution problem — where it can be used again. The second largest user, agriculture, really consumes the water it needs. When water is spread on the fields to irrigate them, less than a third of it drains offer seeps down into an aquifer; the rest is evaporated or is transpired by the plants into the atmosphere. In the arid West, it is estimated that a thousand pounds of water are used and breathed out into the air by the plant in the production of a single pound of dry vegetable matter.

West of the Mississippi, by far the largest user of water — both surface and ground water — is agriculture. In a number of areas such as the irrigated plains around Lubbock, Texas, the Grand Prairie of Arkansas, the San Joaquin Valley and several other areas in Galifornia, and the ricegrowing area in southwest Louisiana, the farmers are making a perennial overdraft on the groundwater reservoirs beneath their farms. In some of these reservoirs in Texas, California, and Louisiana the demand has been so great that sea water is being sucked up into the aquifer from the discharge area.

In the eastern part of the United Stales the industrial use of water has created a number of contamination problems along the coast. In Brooklyn, New York, for example, the heavy use of ground water lowered the water table from above sea level to as low as 50 feet below sea level and started the process of salt-water infiltration. Brooklyn’s problem was accentuated by the fact that the recharge area which supplied this underground water was being slowly covered with buildings and cement, so that now about half of the 70-square-mile area sheds its water into storm sewers and out to sea, while stringent measures are taken to protect the aquifer below from further salt-water contamination. With the deep cone of depression drawing in sea water and half the recharge area cemented over, New York State passed a regulation making it mandatory for any user of large quantities of water for cooling to drill a recharge well and pump the water right back into the aquifer, and New York City drew water for Brooklyn’s needs from the Catskills. These two expedients have been successful in raising the water table. The constant recharge of the aquifer by water that has been used mainly for cooling, however, raises the temperature of the ground water slightly and so makes it a little less useful. It has been suggested that in places where the low temperature of the water is important, a program of winter recharge with the excess of icy water available at that time be started. In the Mill Creek Valley north of Cincinnati, Ohio, where this has been tried, it has proved effective in storing the cold of winter along with the water.

Another form of recharge, and a very elementary one, is to locate producing wells on the banks of streams. As the cool, pure water is pumped from the gravel beds below the stream, the stream water is drawn down to replenish this aquifer.

Such a system is being used by industry near Cincinnati, Ohio. A well beside the Great Miami River, near its confluence with the Ohio, pumps 13 million gallons of water a day from the gravel beds that underlie the Miami Valley. As this flood of water is withdrawn, there is an increased percolation of river water to replace it. The filtering action of the sands and gravels of the river bed produces a purer, cooler water for industrial use. Similar wells have been driven into the sands underlying the Ohio River on the West Virginia shore and have produced pure, uneontanimated water from this notoriously filthy river. The water withdrawn in this fashion eventually finds its way right back into the Ohio River and on to the Gulf, but the underground reservoir from which it was drawn has not been depleted.

But trouble comes when man pollutes the ground reservoirs. In California the manufacturer of a weed killer which contained trichlorophenol flushed the waste from cleaning equipment and floors into the sewage system. This waste water was diluted with 12 million gallons of city waste water daily before it was discharged into the Rio Hondo. Yet, within seventeen days, a number of shallow wells in the area had to be shut down because of the presence of phenols in the water, and lawns and shrubs which were watered with the polluted well water had been killed. Within six months, water contaminated with phenol was being pumped from wells 10 miles away — even though the plant was shut down a month after it began business.

The cheapest method of recharging our underground reservoirs is to increase the inflow of water at the natural recharge area. This method consists of flooding or running water through ditches over land which is porous enough to permit the water to filter down into the aquifer. In some sections of California, mountain streams have been diverted from their natural channels and directed into king ditches winding over the recharge area. In other parts of the state, they have built shallow ponds over this porous earth where water can be made to flow into the aquifer. In the Los Angeles area, water spreading is expected to stop the inflow of sea water which was ruining the aquifer.

The major problem in this type of recharge is to prevent silt or bacterial growth from clogging the porous topsoil and preventing the downward flow of water. The muddy water that follows a flood is usually by-passed because of silt, and the flood basins and ditches must be cleaned of this fine soil periodically. Bacterial contamination, where it becomes a problem, is fought with chlorination.

3

THERE have been several rather fancy variations on these basic methods of recharge. In Dayton, Ohio, the city’s water supply comes from a group of wells located on an island in the Mad River. Jn this way the city takes advantage of the induced recharge from the river. But when the water table is found to be going down, dams on the river raise the water to a point where it can be brought onto the island and run through channels over the sandy surface. This double-barreled attack brings about an immediate raising of the water table below.

In Canton, Ohio, the city has located two aquifers, a shallow one and a deep one below it, neither of which in itself has an adequate supply of water. By tapping both strata, it is possible to draw on the upper aquifer and direct its water through the impervious layer between the two so that it. recharges the lower aquifer from which the city draws its water supply.

Our efforts to recharge, however, are pitifully inadequate for the future, In the high plains of Texas, water is being pumped out at the rate of twenty times the amount that is going into the aquifer, without an adequate means of artificial replenishment or any alternate source of supply — and when the water-bearing sands have been pumped dry, the rich irrigated area around Lubbock will face ruin. In Louisiana, Arkansas, Arizona, New Mexico, Nevada, and Ltah we know that there are areas where overpumping is steadily depleting the underground water reservoirs. The really alarming thing is that we have such meager knowledge of our total underground water supply and the amounts that are being withdrawn from it.

The first step is one of bookkeeping and research. The location, extent, and capacity of the aquifers of the United States must be measured, together with the amounts of water that are currently being withdrawn. Then an accurate estimate of our future water needs must be made and better methods must be found for measuring the capacity of aquifers and for replenishing them.

An experiment run by a government geologist, D. J. Cederstrom, at Williamsburg, Virginia, revealed the fact that an aquifer which had been contaminated with salt water could still be made useful for storage by floating fresh waiter on top of the salt water, like floating cream onto a cup of coffee.

Another recharge experiment will start in the Grand Prairie region of Arkansas this year. This is the center of the largest rice-growing region of America, where for years the planters have been pumping deeper and deeper wells to draw more water from the aquifer than is going into it. Roger Baker, the geologist in charge of this experiment, plans to use the irrigation water, which must be drained off the pondlike fields of rice at certain stages in their growth and usually creates a great drainage problem, and run it back into the aquifer through recharge wells.

These are important experiments which will give us information we badly need. They are steps in the right direction, but they are only halting steps.

We must have information to give to farmers so that they can follow the lead of the King Ranch in replenishing the underground reservoirs (and remember that almost every farm with a farm pond has a surplus-water problem sometime during the year). At the present time we do not have enough facts to give to state legislators who want to encourage such practices by passing good water laws.

The greatest part of this work is currently being done by an understaffed, underfinanced branch of the U.S. Geological Survey. If there is any doubt as to the necessity of more awareness of the problem, one need only point to the fact that outside of California not a single Hood-control plan on the books today calls for the use of our vast underground reservoirs as a place to store dangerously overabundant water, nor even for the study of such a possibility.