Oceanography

The water locked in ice, mostly in Antarctica and in Greenland, is about 1.5 percent of the water in the oceans. But the oceans are so vast that 1.5 percent of them is still a great deal of water-about 5 billion, billion gallons. If we could melt the ice and run it into water mains instead of drawing from rivers, there would be enough water, before Antarctica and Greenland were stripped to bare ground, to take care of needs for thousands of years at the present withdrawal rate. The barrier to using melt-water at the present time is economic. Energy is required to melt ice and there would have to be some way of moving the water to places where it would be used, a further addition to the cost.

The idea of using the ice caps is not so far from being economically reasonable as one might suppose. A fascinating suggestion was made by Professor John Isaacs of Scripps Institution of Oceanography-to tow an iceberg from Antarctica, and collect the fresh water as it melted offshore of water-starved southern California. Isaacs estimated that two battleships would be required for towing the ice to San Diego. The project has not yet gone forward, but it is not because the towing costs would be too high, nor because the iceberg would melt en route, nor because the amount of water gained would not be a significant addition to the local supply. Instead the difficulty is the lack of a way to collect the fresh water as the iceberg melts. That particular problem is a difficult one but apparently not impossible to solve, because the melt-water from an iceberg is less dense than salty sea water so the fresh water would tend to float on the sea water surrounding the iceberg and might be collected before the two mingled.

A good sized iceberg may rise one hundred and fifty feet above the sea with seven hundred feet or more beneath the surface. A cubic iceberg eight hundred feet on an edge would melt to about three and a half billion gallons of water, or about 1 percent of the entire daily United States demand. The population of San Diego County is just about 1 percent of United States population. Therefore, if all the water could be collected from an iceberg, San Diego County needs could be served but an iceberg every day would be needed to do the trick! At any rate, it is comforting to know that the great glaciers and icebergs exist, and that an increasingly clever technology may some day solve the cost problem.

A scheme akin to Isaacs’ in imaginativeness, but further from possible achievement, has been proposed in which large ice-balls would be sent by pipeline from Antarctica to Australia, the heat of friction melting them en route so that they would arrive on Australian croplands as ready-to-use irrigation water.

The amount of usable water in lakes is only about 0.3 percent of that contained in glaciers, but lakes are ordinarily much more conveniently located. Their water can be used without supplying, by one means or another, the tremendous amounts of energy required to melt large masses of ice. The lakes of the world contain about as much water as flows down all the rivers in a year. Lakes are delicate systems; if we began to use them faster than they are replenished, the effects would be so complex and far-reaching that it is almost impossible to estimate what all the consequences would be. If we started to draw water out of Lake Erie, for example, at a tremendous rate, the normal outward flow down the Niagara River would be halted but the inflow to the lake would not be increased. If lake level were lowered 100 feet, water could no longer circulate as it now does. Niagara Falls, between Lake Erie and Lake Ontario, would dry up and Lake Ontario would be cut off from its water supply. We find that use of lakes turns out to be much like use of rivers. We can take from lakes part of what goes into them, or even all that goes in, if we return it; but when we begin mining them, using them beyond the level at which they are restored, the results will be drastic and complicated. Temperatures will change, the fish population will be affected, new kinds of plants will grow, many of the present ones will die, local weather will be affected, even recreation on lakes will be changed. It is not impossible, perhaps, to manage lakes while they are being depleted, though it would be extremely difficult and costly. Lakes can be used as reservoirs to tide us over during years of drought, but long term withdrawals from lakes probably cannot exceed the amount of water flowing in and out of them. Thus they are really only a part of the river system, when long-term water supply is assayed.

The major source of readily available water not being exploited is the underground supply. The total amount in the pores of rocks may be as much as 20 percent of the whole oceanic volume, but only a small fraction can be recovered. The mineable underground water is about a third as much as is locked in ice, and half exists within twenty-five hundred feet of the surface, where it can be fairly easily drilled into and pumped out. The other half is not only expensive to find and retrieve but tends to have too great a salt content for most uses. In the United States the easily reached high quality supply would last five thousand years if we switched to a policy of getting all our water from underground storage. Again we see that the fresh water supply, as a total available amount, is not a serious current problem. In the case of groundwater the difficulty, like that of ice but not so severe, is in its geographic distribution. The eastern and central states have abundant supplies, whereas the western states are in serious trouble. In the Los Angeles area the problem is acute; there is dense population, low and irregular rainfall, and limited groundwater storage.

In the United States about one third of the flow of all streams is used at least once, so that we are beginning to use a significant fraction of the major readily available water supply. At the present rate of growth of use and of population we will come pretty close to using an amount of water equal to total stream flow by the year 2000. But use does not necessarily consume water. In fact we have not even included under use the water that makes electricity at hydroelectric stations, where water turns the turbines and is not changed chemically even though it has performed an important service. Water is consumed only if, as a result of use, it does not return to the stream system, from whence it can be withdrawn again. Eventually, of course, even though it has evaporated or has been taken out of circulation in manufacturing, it will return as rain or snow to land or ocean, and so find its way back some day to the stream supply. It is obvious that some water can be used more than once. It can be withdrawn from streams, used, returned to the stream and used again. The water of the Ohio River is used three times over in its course to the Mississippi, and one of its tributaries is used seven times. If there were no losses by evaporation when water was withdrawn, and if everyone returned the used water in the condition in which he found it, the present supply would be sufficient forever. If it were not for evaporation losses, treatment of used water, perhaps polluted by minor contaminants but not salty, could almost solve our problems. In theory, every house could have a tank and all the water from dishwashing and bathing could go through a purification plant and be returned to the tank. But there would be a net loss; water is drunk, used for gardening, evaporates from the swimming pool, is lost as steam from the teakettle.

The best estimates are that water consumption today is only about one third of water withdrawal. Most of the consumption is attributed to evaporation from irrigation. Little of the evaporation loss is directly from water that is spread on the fields, but is due to evapo-transpiration of growing plants. An acre of com can withdraw three thousand gallons of water from the soil each day and send most of it out into the atmosphere through the leaves as water vapor. Of course what has evaporated is available again at some future time. The general water cycle is one of income, storage, and outgo, much like a checking account.

There are quite reliable figures for the water loss during irrigation; only 40 percent of all the water used is returned to streams. This is in contrast to municipal use, in which 90 percent is returned, or industrial use, in which 90 percent is returned. The problem of how much water is lost is still a tricky one because no one knows how much of the water evaporated from a lettuce field in California ends up in the Mississippi River after it has condensed and fallen as rain in eastern Iowa.

But most predictions of the growth of irrigation indicate that it will soon begin to lower significantly the volume of the stream flow of the whole earth.

The degree of reuse of water is determined to a large extent by the change in composition that takes place when water is withdrawn, used, and returned. Water used for baths or showers is little altered. It has had a little dirt and soap added, but it is otherwise unchanged. If bath water could be isolated from the household waste water and treated it would cost little to restore it to its original condition. In contrast, consider the water that emerges from kitchens that have various types of disposal units that grind garbage into sludge that is flushed into drains. This water is loaded with a variety of ground-up organic materials that must be oxidized away or settled out before the water returns to potable quality.

Industry poses the same variety of problems. Water used as a coolant in steel making returns to its source unchanged, except for added heat. However, water used in some of the chemical treatments of iron and steel becomes rich in chromium, sulfuric acid, or other chemicals. To clean up cooling water costs little; to clean up chemically altered water costs a lot. There is no simple solution to the reuse problem.

To return water to streams in a condition similar to that in which it was taken requires separation and special treatment of the water, according to the specific uses to which it was put. The cleaning treatments cost money, so that the problem is one of economics, rather than merely of supply or methods for cleaning.

In addition to the constant supply of water that comes from rain we must consider the amounts stored at present in lakes, in glacier ice, and underground. All of these natural reservoirs can be “mined.” By mining we mean using a supply for which rate of withdrawal exceeds rate of replacement. We cannot view mining of water reservoirs as a practical approach in the long run. How long could we exist if we did not use the normal daily atmospheric supply, but relied entirely on melting glaciers, or on draining the Great Lakes to supply water to Arizona? If we do not insist on a perpetual water supply and decide to take water only from glaciers, lakes, and underground, how long could man survive before all these reserves were depleted?

Now we get a hint of the importance of having good “communication” between the Atlantic, the Pacific, and the other oceans. The freer the circulation, the smaller the differences in climate from equator to pole; the more restricted the circulation, the greater the climatic contrasts. A planet with landlocked seas, even though they had just as much water as earth’s oceans, might have greater polar ice caps and hot seas at the equator.

When sea water evaporates, the salts are almost entirely left behind, and the fresh water vapor moves into the atmosphere. As the vapor rises it cools, condenses, and finally rains back on the sea. If there were no continents the system would be simple enough. For the oceans as a whole, the surface would be lowered about three feet each year by evaporation, but the depth would be restored by condensation and resultant rain. Total evaporation would equal total precipitation.

The Water Cycle

There is a time lag between evaporation and rain return; the evaporated moisture travels long distances in the atmosphere before it comes back to the oceans. Part of the water evaporated from the oceans moves over the land before it condenses, then it falls as rain or snow on the land, where it may evaporate again, or collect as ice, or sink into the ground, or run off across the surface in rills and brooks to coalesce into rivers that flow back to the sea. Given enough time, all of the water in the oceans will pass down the rivers to the sea. Cleopatra’s bath water has run to the sea and mixed throughout the oceans. About 5 percent has already been evaporated and returned to the continents as rain. A few molecules of her bath are present in every tub full of water drawn today.

Yearly precipitation on the continents averages a little less than the three feet that falls on the sea, enough to cover the land to a depth of two and a half feet. Two thirds evaporates into the atmosphere and comes back to the sea as rain, and about one third returns to the oceans via streams. When it first falls and begins to run across the land surface, rain is satisfactory as a water supply for almost every purpose. It can be drunk; it has just enough salts inherited from the sea so that it doesn’t have the bad effects of perfectly pure water, yet there is too little salt to have toxic effects. A generation or two ago many homes had a barrel or tank in which rainwater was collected from the roof for drinking and washing, as is still done in Bermuda today.

If we neglect distribution problems engendered by the fact that rain refuses to fall where we want it to, and assume that all that falls could somehow be collected before it evaporated, we come up with a maximum figure for the naturally available water supply. By multiplying the total area of the earth by the average feet of rainfall, we arrive at about forty million gallons of water per year for every person on earth, a total of one hundred and forty million billion gallons.

The sun is very kind in the share of its energy it gives to the water cycle. The amount of energy required to evaporate the one hundred and forty million billion gallons of rainwater is half of the total radiation of the sun received at the earth’s surface.

The water in the oceans, the clouds in the sky, and the ice of the polar seas are all parts of the dynamic solar energy-transfer system that makes the earth run. Our available fresh water comes from this global rain and ice-making machine.

The controls of climate and rainfall depend on just how the solar energy received is distributed to the atmosphere, the oceans, and the continents. The balance is delicate indeed, but tenacious. The earth is just emerging from a great Ice Age, and while there have been other ones in the past, things have never gotten so far out of control as to freeze much of the oceans into ice, or to boil them into the atmosphere as steam.

The earth loses as much energy back to outer space as it receives from the sun (plus a little bit more that escapes through the surface from its internal fires), and has maintained this balance closely for billions of years. Equality of gain and loss has held the average temperature of the surface environment, despite local variations, quite constant. Rocks containing fossils of organisms like those of today that were deposited in the oceans hundreds of millions of years ago show that sea water was about as warm (or cold) then as it is now.

The secret of the ocean thermostat is the ability of water to soak up heat without much temperature change. It takes a lot of heat to raise water to the boiling point and almost ten times as much again to convert it into steam. Even though there may have been great variations in solar energy received at the earth’s surface through time, the oceans have kept the temperature constant. When one part of the ocean is heated circulation results, so that it is not possible to boil water at the equator while keeping it frozen at the poles. The faster it is heated, the faster it circulates. The ocean basins are linked together and thus behave as one immense pot-heat part, heat all.

Because it takes so much heat to cause evaporation and so much must be removed to cause freezing, water maintains its liquid state in most natural circumstances. If the energy from the sun were to diminish for a long time, the earth would lose heat to space faster than it would gain heat. Glaciers and ice caps would grow but heat would be generated by the change from water to ice, and, rather than falling below freezing, temperatures would remain at the freezing point until all the water was frozen.

It takes about five times as much heat to cause a temperature change in water equal to the same change in rock. The scorching sidewalk beside the cool puddle is a model of the continents and oceans. It takes little heat to warm rock, and because the rigid concrete transmits its heat but slowly downward, its surface temperature rises rapidly in the sun. Not only does the water of the puddle require more heat per pound for temperature change than does the rock, it also circulates so that the whole puddle must be heated, evaporating eventually into water vapor. For every ounce of water evaporated fifty ounces of rock can be heated ten degrees. The same relation applies to the continents and oceans. In central Asia, summer temperatures may reach 90° F, and in winter may drop to 70° F below zero, while the whole ocean range is only from 32° F to 85° F, and more than 90 percent of all the water is a few degrees above freezing.

If we were going to make another planet for human habitation, with a free choice of materials, we would unhesitatingly demand that the planet have a water ocean to provide maximum safeguards against being scorched or frozen. It takes one unit of heat to warm an ounce of water one degree, it takes almost six hundred units to evaporate it, and eighty units must be removed to freeze it.

In 1960, industry and agriculture in the United States each used about one hundred and fifty billion gallons of water a day. Industrial needs are large and varied. It takes, for example, a hundred thousand gallons of water to manufacture an automobile; an average Sunday paper consumes about two hundred and eighty gallons of water in its processing; a ton of steel requires sixty-five thousand gallons of water in the making. The location and size of water supplies determine to a large extent the profit or loss in a business operation. A twenty-two unit apartment house may require more than three thousand gallons of water daily; a laundromat with ten washers may require more than 1,800 gallons of water a day; a car wash that can handle twenty-four cars an hour will need nearly 8,000 gallons of water daily; a large paper mill can easily use more water than a city of fifty thousand people.

Clearly these businesses are not inexpensive to operate in locations with poor water supplies. This water may cost as much as twenty-three cents a thousand gallons from the municipal supply. To operate a laundromat successfully, it may cost an additional three to seven cents per thousand gallons to have “soft” water. Special processing for many industrial water uses adds to the cost.

Not only does the world food supply depend upon water, economic development occurs where there is sufficient water to support, first, the population, and later, the industrial demands. One has to know only a little history to know that civilization flourished with adequate water supplies, and that industrialization has occurred in areas of abundant water for power and for transport of goods. Populations have been forced to move with changing water supplies. Archaeologists have traced the growth and decline of Indian villages in the southwestern United States as water declined in abundance or purity. It has been man’s ability to transport enough water from areas of abundant supply to less favored areas and to otherwise supplement local supplies that has permitted the development of arid and semiarid regions for agriculture and industry. The technologic demands for further such development will certainly become greater in the next few decades as land with marginal water supplies is pressed into use.

There is much value in the idea that land should be reserved for the use to which it is best suited. Covering good agricultural land with parking lots and highways and tearing down orchards to build more houses takes out of production land with high agricultural yields and eventually forces cultivation of land that does not have adequate water for growing crops, requiring the installation of expensive irrigation systems.

The same dependence on water plagues industry. As water demands increase and supply becomes scarcer, or more polluted and more expensive, industry moves toward abundant and inexpensive water supplies. Industrial water generally must be of at least as high quality as drinking water; in some instances even more restrictive specifications must be met. Some industries buy water from public supplies, and then treat it further to meet individual needs. The amount of salt in water used in ultra high pressure steam power plants can be only 1 ppm, while the manufacture of rayon requires water with no more than 100 ppm total dissolved solids. Whiskey can be distilled with water containing 1,000 ppm total solids, so that distilleries may remain longer in polluted areas than steam power plants! Water for cooling, used in numerous industrial processes and accounting for a high percentage of industrial water use, must be non-corrosive and contain extremely low percentages of minerals. Another important factor is temperature; it is obviously important to avoid expensive pre-cooling before water can be used. Some industrial uses for distilled or demineralized water are in leather-finishing processes; the tanning processes sometimes require water with low bacterial content. Each industry has its own special needs for various types of water.

It was once possible to produce power with a wooden paddle wheel and natural stream flow. The water was fresh and clean, and even if it did become polluted the effect on the operation of the mill was small. Today it takes millions of gallons of high quality water to operate boiler-powered electrical plants, and millions of gallons of stream water to produce hydroelectric power. Electricity production accounts for sixty percent of industrial water use.

Why other industries require so much water is often a bit obscure. The uses for water in food canning will serve as an illustration. Water of drinking quality is used to clean raw foods, which are then transported to various operations in the factory by belts, flumes, and pumping systems (accounting for a major portion of water used). After peeling, fruits and vegetables are rinsed thoroughly in water-especially important if the peeling has been done chemically. Green vegetables are put into hot water or steam to inactivate enzymes and to wilt leafy vegetables to facilitate packing. Very high quality water, free of chlorine, is used for packing, or is used in packing syrups and brines. Containers are sterilized and cooled, both steps using large quantities of water. And finally, water may be used to transport waste materials from the factory.

As another example, the textile industry uses vast quantities of water for washing raw materials, in dyeing and bleaching, and for washing the finished product.

When we survey water use today, we find that industry and agriculture use 96 percent of the total consumed, and that only about 4 percent goes for direct personal uses. One important fact emerges-we tend to think of drinking water as being purer than that for irrigation and industry, whereas the facts are that the tolerance range of humans is greater than that of some plants or of the canning industry. Moreover, as technology becomes more complex, the necessity of treating natural waters for specific uses also grows more involved and costly. As our knowledge of botany, of zoology, of all other aspects of living increases, we find that more and more controls on water composition are desirable.

Study of the water requirements of many species of plants shows that some thrive on high sodium waters; others wilt. With a rapidly expanding world population, it becomes more and more important to reap the maximum production from each acre of fertile land. We find that plants must be fed a diet of water whose composition is tailored to the individual crop.

We are beginning to realize that the natural drinking water supply, even without problems of pollution, or naturally introduced organisms, is not necessarily always the best. Many natural supplies have enough fluoride to cause bone and tooth damage; others have enough salt to be damaging to sufferers from high blood pressure, even though they are satisfactory for normal healthy persons. At the same time that we are discovering the significance of the many elements occurring naturally in water, we are adding new substances faster than their effects can be assessed.

Whatever the solution to the ethical and political problems of control of water composition, some predictions can be made. “Pure” water, water like that we must drink but with even less dissolved material, will be required for most industrial and agricultural uses. With increasing utilization of stream and underground water we find that the great reservoir-the oceans-will be needed more and more. If we are to use the oceans they must be at least as un-salty as streams. This gives us a clear target for the future.

What are the requirements today and of the future for this kind of water? In 1960 the United States used three hundred billion gallons a day; in 1980 it is estimated that withdrawal of water will reach six hundred billion gallons a day, and that by 2000 it will be nearly nine hundred billion gallons daily. Water use grows faster than population. The estimates indicate that when population is doubled, water use will triple.

If we can hope that by the year 2000 the rest of the world will have reached a level of affluence more nearly equal to ours, we must think of water requirements based on per capita numbers. If we use nine hundred billion gallons a day for three hundred million people, we will be operating at a rate of a little over three thousand gallons per day per person. The best estimate of world population at that time is about seven billion people. If so, the amount of fresh water required will be close to twenty thousand billion gallons a day, an amount about equal to the entire world stream flow.

True, a world in thirty years with uniform international affluence is not very realistic, but even if the growth of affluence is slow, the growth of population is not, so a fresh water demand of this magnitude is certainly foreseeable under any circumstances. The question arises-is that much fresh water available? If not, what can be done about it?

Irrigation is one of man’s oldest engineering endeavors. From hand carrying of water to thirsty crops man progressed to digging ditches and building dams to store and diverts water. Perhaps the beaver supplied the complicated model for the first man-made dams. Hammurabi, the ancient Babylonian king, described irrigation when he wrote, “I brought the waters and made the desert bloom.” We are doing the same thing today, but we have moved to engineering of such magnitude that the giant and far-reaching Feather River project of modern California will eventually have the capacity to deliver two thousand billion gallons of water a year, much of which will benefit agriculture.

The temperature of irrigation water is significant. Warming basins are often provided to bring water to the proper temperature for irrigation; this varies with each crop so that no average figure can be given. When water was first released from Shasta Reservoir for summer irrigation of rice in California, crop damage resulted from the forty-five degree water, sixteen degrees colder than that previously used.

There are approximately four hundred and sixty million acres of cropland in the United States and more than forty-four million of them are irrigated. This 10 percent produces roughly 25 percent of the total value of crop production. Although many areas are already using all the water available to them, irrigation is expected to increase both in the United States and abroad.

Plants as well as animals are biological factories for food production. The water they use affects not only the product but also the factory efficiency. The water they are given must be tolerable to them and safe for human consumption at the end of the food chain. The recommended limit of dissolved solids in water for agricultural uses is about 700 parts per million whereas drinking water for man may have as many as 1,000 ppm dissolved solids.

The amount of water required for agriculture will become greater in the future as population increases. There are already three and a half billion people in the world and by the year 2000 there may well be seven billion. It is predicted that the 46 percent consumption of water by agriculture in the United States will increase to 62.6 percent by 1980. Already Japan, hard pressed by a high population, uses 80 percent of her water to grow rice, and Israel, now using most of her water for agriculture, depends entirely on irrigation for food production.

As an indication of how much water is needed to produce the world’s foods, six hundred and fifty thousand gallons of water are required to produce thirty-two bushels of wheat; three hundred gallons of water are needed to produce two and a half pounds of bread; a pound of beef represents twenty-three hundred gallons of water. These figures do not include the amount of water used in processing or transporting food products.

As bacterial spores are perhaps the only vegetable organism having as little as 50 percent water, we can say that plants are mostly water. Lettuce, cucumbers, spinach and asparagus are 95 percent water; tomatoes and carrots are 90 percent water; p0tatoes are 80 percent water.

Anyone who has weeded a garden has some idea of plants’ extensive water collecting system. Most root zones are roughly six feet below the ground surface, although some plants put down roots too deep to obtain water. Trees with roots reaching down forty to eighty feet are not uncommon.

Other plants can never reach down far enough to find ground water and their roots may instead spread horizontally beneath the surface. A desert cactus, for instance, may have twenty miles of roots, lying close to the surface so that quickly penetrating rain can be absorbed before it rushes down beyond the root zone. The tiny root hairs may take up many miles in search of water; a single rye plant may have 380 miles of these root hairs.

Another agricultural need for water is for livestock. Although the amounts vary with climate, animals require much more drinking water than humans. Sheep can survive on one and a half gallons a day, while cattle need eight or ten gallons a day and horses as many as fifteen gallons a day. The great herds of animals grazing in the western states alone require staggering amounts of water. One estimate says that there are a hundred million cattle and ten million horses among the United States livestock population. Even with these numbers, the amount of water used for livestock is small in relation to other uses.

Animals can tolerate much more salt in drinking water than can humans. Poultry can survive on water with 3,000 ppm salt and sheep can take water with 10,000 ppm salt. A low salt intake from water is often supplemented with salt blocks. An awareness of animal tolerances of each element in the water supply is as necessary as is this knowledge for control of drinking water for man.

Particularly stringent water quality control is necessary in processing of dairy products. Water for milk processing must be free from all harmful bacteria, yeasts, and molds. And because the flavor of milk is so easily influenced, processing water must be free of tastes. Another strict requirement has been discovered for water used in egg-washing machines, where water containing more than 1 ppm iron may accelerate spoilage.

Man seems to have been molded in his evolution by the water he must drink. If a list is made of the average concentrations of many of the elements in the average river water of the world and beside it is placed a list of the maximum concentrations of those elements that have been established by the U.S. Public Health Service as acceptable for human consumption, we see that injurious concentrations of elements in drinking water are high if the amount naturally present in the rivers is high, and are low if the amount naturally present is low. This is mute testimony that man had to evolve in harmony with the available water. The human machinery is geared to its supplies; anyone born with the ability to tolerate lead in large quantities would derive no survival benefits from his unique talent. In fact, if he had a high lead requirement he would be in trouble, because it is a rare water indeed that contains more than a fraction of a part per million of lead. On the other hand, imagine the difficulties of the person made sick by two or more ppm calcium. He could not use the public water supplies anywhere in the world and would have to set up a private rain collecting system to take care of his needs.

In most communities the water for domestic and municipal uses comes from one common supply which is of drinking quality. It is more convenient to have one supply, maintained at drinking water standards, than supplies tailored to every need. Domestic uses vary greatly from place to place. Water for washing and plumbing and for watering lawns and gardens are some of the uses which help to account for the average domestic consumption of one hundred and fifty gallons per person each day in the United States. This is a very rough estimate and may range from as little as five gallons by a water miser to more than two thousand gallons, depending not only upon the affluence of the household but on the climate as well. To have some idea of how much water an individual uses in a day, it may be of interest to note that the average washing machine uses about twenty-three gallons of water, a dishwasher uses fifteen gallons of water, one flush of the toilet about four gallons, about half a quart fills an ice cube tray, four quarts are needed to cook a pound of spaghetti.

Although this domestic water is safe for drinking, it is sometimes treated for “hardness” caused by high mineral content, chiefly calcium and magnesium. The ring around the bathtub comes from the reaction of calcium in hard water with soap. Until the early 1940S the cost of water softening was nearly offset by a saving in the amount of soap otherwise used, but with the advent of the modern detergents this has changed. A familiar phrase used to promote many detergents is, “works even in hard water.” However some areas of the country have water so hard that even these detergents are not effective unless the water has been softened. In such areas the municipal supply is softened before it is distributed; otherwise many households install their own water softening units, adding considerable cost per gallon for such a benefit.

Some specialized requirements may be found in home use of water. To prevent corrosion, a steam iron should be filled with distilled water rather than the mineral-laden water from the faucet. Likewise, air-conditioning systems require water with a low corrosive action.

As well as domestic uses, demands on public water supplies may be for recreational facilities. The quality of water for swimming and bathing, while not necessarily as high as that for drinking water, must be safe for human contact. Though the mineral content of bathing water may be of little importance, the bacterial content is.

Another common use of municipal water is fire control, and any water system must be able to deliver a dependable supply in emergencies. Because modern fire equipment uses far more water than the old bucket brigade or horse-drawn pump, water supplies must now be planned with capacities to deliver anywhere from a few hundred to more than twelve thousand gallons a minute, sometimes for many hours.

Domestic and municipal uses (other than industrial) account for less than 10 percent of yearly total water consumption in the United States. Whereas Parisians of the eighteenth century used only slightly more than one gallon of water daily per person, and today in some parts of the Middle East the average’ person may use only about three gallons of water daily, most Americans have become accustomed to plenty of clean clothes, frequent baths, green lawns, shining automobiles, and abundant water for drinking and preparing food.

Our personal uses for water are small compared with other uses, though they often seem the most important ones. Even more essential to survival is water for agricultural purposes. Today agriculture accounts for more than 46 percent of total water use in the United States. Again, the requirement is fresh water and in general of drinking quality.

There is a great variety of natural sources-minerals in rocks and soils, as well as artificial ones-pesticides, chemical manufacturing processes, burning of coal and oil, old thermometers, barometers, radio and television tubes, antifouling paint. Although the total tonnage of mercury exposed to air and water is small, compared to an element like iron, serious local difficulties can develop where disposal is in places where methyl mercury can be formed and work its way into the food chain.

The mercury poisoning that occurred at Minimata Bay in Japan is now a widely known incident. Inorganic mercury was dumped into the bay as waste from a large chemical plant. In 1953 a strange nerve disease appeared among residents of the area. It was traced to methyl mercury-bearing fish from the waters of the bay into which mercury wastes had been dumped. Even though the dumping practice has been stopped, the bottom muds still contain mercury, which can be converted to methyl mercury, released to the water, and so make its way from fish to man.

On the other hand, common salt, found in most waters, can be tolerated well beyond the tenth of one percent that limits the usual natural mixture of dissolved minerals. Even sea water, which contains 35,000 ppm dissolved salt, can be drunk slowly in small amounts, but the upper limit of salt content in water supplies for constant use is about 1,000 ppm, with 500 ppm being preferable. In arid countries much higher salt content is tolerated. In parts of North Africa drinking water with up to 3,000 ppm salts is used.

If a mineral is required for maintenance of an organism and is not provided in adequate amounts in foods, it must be artificially supplemented or be present in water. The classic example is that of iodine. Insufficient iodine causes an enlargement of the thyroid gland called goiter. In Midwestern United States the water supplies are low in iodine. Goiter was a widespread disease there until it became common practice to add iodine to table salt. In correcting iodine deficiency, it was simple to do it in a way that permitted each person or family to make a decision about supplementing iodine intake by using iodized salt. An alternative method would have been to increase the iodine in the public water supplies, in which case the consumers would have had no choice but to be medicated. We see in the iodine example the basis for one of the most controversial ethical questions of the day. Any treatment of water necessarily adds or removes something and so constitutes a mass medication in the broad sense. The kinds of water treatment that are generally acceptable involve addition or subtraction of substances that are absolutely necessary for general water use. The additions should be harmless, ideally without effect on color, taste, odor, or on any use to which the water is put. This ideal is not attainable, but basic water treatment-aeration, filtration, and chlorination -comes close to fulfilling these goals.

The great fluoride battle still rages; it has not been possible to solve it as easily as the iodine situation. The limits on the concentrations of fluoride that are so low that tooth decay is not inhibited and those that are so high that teeth are damaged are narrow; one half a part per million is too little and two parts per million are too much.

Even these narrow limits are not generally applicable; some people drink more water than others and thus get more fluoride. Especially in the case of children the amount of water drunk is generally directly correlated with the weather. One part per million fluorides may be too much for one person and two parts may be too little for another. To make the situation even worse, most of the direct benefits of fluoridation are restricted to the under fourteen age group. And finally, no entirely satisfactory optional substitute for water in controlling fluoride intake has been developed.

Silica, one of the most common constituents of ordinary rocks, is a major dissolved mineral in many waters, yet it seems to have no physiological effect at all; it can vary sixty fold from one water to the next without any apparent consequences beneficial or harmful. Beer, for example, contains four or five times as much silica as most drinking waters but it is obvious from the enormous quantities of beer consumed that silica has no bad effects.

Copper is an essential element for human metabolism. The normal diet may provide only a little more than is required so that an extra supplement in drinking water, although it may impart color, is beneficial. Copper is sometimes added to water to control growth of algae. Iron and manganese, in large quantities, may also cause objectionable color and taste, but they too are necessary for good health.

Cadmium and chromium are not essential elements and can even be highly toxic to the human body. Selenium, zinc, and nitrate also belong to this group. Nitrate is especially dangerous for infants who may drink it in water or milk.

There are many other substances in the water supplies that must be tested and controlled, but to speak of each one and its effects would require chapters if not books. One final consideration is the delivery of a safe water supply, which depends not only on the purity of the source, but on the quality of such equipment as water mains and storage tanks involved in the delivery to the consumer. Maintenance of equipment, which could corrode and release poisonous metals to the water, is vital. Lead pipes were once widely used in plumbing but they have been almost entirely eliminated except to carry corrosive waste waters.

Although it is true that most stream and lake waters in a virgin land could be drunk untreated, the establishment of a small settlement near the water source is sufficient to create local health problems and make water treatment necessary. Of the present 3.5 billion inhabitants of the earth, at least 1 billion regularly drink unsanitary water. Of these, 500 million are continually sick and 10 million die each year. They are the victims of bacteria and viruses and parasites that breed in the digestive tracts of humans and animals, and which, if they get into the water supply, cause diseases like typhoid, cholera, and dysentery. Some of the most important tests performed on drinking water supplies are for bacterial content. Only relatively recently have we learned to control water-borne bacteria and viruses. It was unsafe drinking water that caused massive cholera epidemics in London in the 1800s, yet it was not until the latter part of that century, under the influence of Pasteur’s theories, that the idea was abandoned that sickness was caused by impure “vapors” in the air and the necessity of disinfecting drinking water was understood.

Control of microorganisms is by filtration, aeration, and chlorination. Filtration through beds of sand and gravel removes suspended material and some bacteria and dissolved organic particles and clarifies the water; aeration destroys organics and kills many bacteria. If water is thoroughly mixed with air, oxygen “burns” the organic material and the bacteria have little left to live on. Streams with rapids are said to clean themselves in a short distance because of the excellent aeration. Sluggish rivers with much natural organic material or that have been polluted by organics, release foul-smelling gases as bacteria that live in the absence of oxygen break down the organic material. In water treatment plants the water is sprayed into the air to purify it and to improve its taste.

Chlorination is used around the world as the last crucial stage in removal of microorganisms. Most dangerous species yield to it easily but there are a few bacteria that are extremely resistant. They may ordinarily be absent from a water supply, but if they get in they may cause serious epidemics before they are discovered and the chlorine level and length of treatment are adjusted. It is not feasible to test routinely for all possible pathogenic organisms so the coliform bacillus is generally counted as an indicator of the presence of other bacteria. If coliforms are at a low level then most other harmful bacteria are also found in small numbers. Water containing more than about twenty-five coliforms a quart is unsafe.

Drinking water is also carefully and continuously tested to insure that other undesirable qualities such as taste, color, and odor are kept to a minimum. Iron is one of the worst offenders; it gives water a characteristic taste and can stain clothing at only two ppm. Many well waters with dissolved iron are clear when they come from the faucet but quickly precipitate a yellow iron oxide when mixed with air. The oxide is harmless if drunk but it stains glassware, sinks, cooking utensils and laundry. Waters with dissolved iron often carry a trace of hydrogen sulfide which, in concentrations far less than one ppm, gives a distinct rotten egg odor to the water. All kinds of new tastes and odors entering water supplies today are traceable to organic pollutants of a wide variety.

Today, with all kinds of new compounds entering the water supplies, the specification of allowable limits has become almost impossible; new substances are being added faster than their effects can be assessed. In addition, the toxic effect of a compound may be severe when it is tested alone, but when mixed with all the other constituents of drinking water it may be neutralized in one way or another, or it may combine with other substances in such a way as to become more toxic. The poisonous effects of equal amounts of zinc and cadmium are worse in waters also high in calcium and magnesium.

The quality control of water is compounded by the fact that not only does the water have to be safe to drink with respect to its individual components, but also with respect to the rest of the environment. For example, lead limitations set for water take into account other sources of lead-in food and beverages, in the air, in cigarette smoke. The problem is to try to guess how much of this generally unregulated intake can be combined with the intake from water before toxic levels are achieved.

In general, the Health Service bends over backward in its specifications of the maximum tolerable amount of the various elements, but every once in a while comes a rude shock from some unsuspected effect. The kind of complication that is hardest to anticipate is the behavior of various elements during their successive travel through the food chain. Water with a given composition, drunk directly by humans, may be perfectly safe, but one of the substances in the water may be enriched in the tissues of other water users, either plants or animals, and then enriched again when one animal preys on another. If the final predator is eaten by humans, toxic concentrations may take their toll. In a sense, then, the water may be satisfactory for direct use but dangerous when considered in terms of its total utilization. DDT, originally at a concentration of only one hundredth of a part per million, has been reported as one thousand parts per million in fish that have eaten fish that have eaten microorganisms from the water originally containing dissolved DDT.

The amounts of different kinds of dissolved mineral matter that can be safely drunk differ widely. The merest trace of lead or arsenic is dangerous because they are cumulative poisons, and, although the amount taken in each day might be harmless, the buildup through the years can produce chronic illness or death. The early symptoms produced by many cumulative poisons weakness, stomach upset, headache-are so common that they can be attributed to a hundred other causes and are seldom properly recognized. By the time a correct diagnosis is made, internal damage may be irreparable, and there is no way of dispelling lead or arsenic deposited in bones or tissues.

The problems that are beginning to emerge in relation to mercury are typical of the complexities that are encountered today when detailed investigations are made of the occurrence and effects of a toxic element. It has been known for a long, long time that the liquid metal mercury was dangerous. When mercury from a thermometer or barometer is spilled and separates into thousands of tiny droplets, the drops release mercury vapor into the air. If the droplets are left on the floor of a poorly ventilated room, so that the vapor can be inhaled, damage to the liver and kidneys results. Until recently this seemed to be a minor and local peril that could be avoided by a little knowledge and attention to cleaning up mercury spills.

Then two things happened. People began to search for poisonous substances in the environment, and simultaneously a highly sensitive analytical method was developed for mercury detection. It became possible to test for the presence of mercury at hitherto impossibly low levels, and thus to find out just where it occurs and where it is concentrated. During the research on mercury occurrence in the environment, the presence and effects of mercury vapor from liquid mercury droplets were corroborated, and in addition, a new and disturbing relation was discovered. If mercury compounds are discharged into water bodies they accumulate in the sands and muds beneath the water. There, under the influence of microorganisms, mercury compounds can be transformed into an organic mercury compound, methyl mercury. In this organic form the mercury is mobilized and can be utilized and concentrated by marine or fresh water organisms. Moreover, as methyl mercury, mercury becomes far more poisonous than mercury vapor or other inorganic forms of mercury. In man it seeks out the nervous system, where accumulations of no more than a few millionths of total body weight are enough to cause paralysis and death. If methyl mercury enters the body, it takes about seventy days before it is excreted, so a safe daily intake is less than one seventieth of the miniscule amount that causes severe nerve damage.

The current situation with respect to mercury is unclear.

Population pressure, growing individual water use, severe local water problems, and a growing consciousness of the far-reaching effects of some pollutants force us to look at the Earth’s water resources with an eye to measurement.

If we regard the total water in the oceans, in ice, in streams, lakes and rivers, and underground, as an available total supply, the water problem seems to disappear. When 71% of the earth’s surface is covered by oceans averaging two and a half miles deep, how could there be a water shortage? The great Pacific Basin covers half the globe; there were times in the flights of the earth-circling astronauts when they could see almost half the earth at once and yet see only an ocean, dotted here and there with a few tiny islands.

One way to try to visualize the total amount of water is to make it into ice cubes, thirty miles on an edge, each one big enough to cover up most of the city of New York and extending up to the limits of the atmosphere. We would have to melt 12,000 such cubes to make the oceans. Compared to the oceans, the amount of water at anyone time in all the other “reservoirs” is tiny. We think of streams and lakes as important but they contain much less than 1 percent of the total amount of water on earth. We hear of the dire consequences of melting all the glaciers, which would raise sea level two hundred feet and destroy hundreds of coastal cities, yet this two hundred feet on a global basis is only 1 Y2 percent of the depth of the oceans. Underground water, water trapped in or moving through the pores of rocks, is the second greatest supply of water and may be as much as 10 percent of the oceanic total. We estimate that all these reservoirs together contain four hundred billion, billion gallons of water.

Another way to look at the total supply is to divide it by the number of people who need to use it. A quart and a half per day is required for sheer survival of every human being. There are 3.5 billion people on earth; what is each one’s share of the total? The answer is somewhere in the vicinity of 120,000 million gallons of water for every human being now in existence. If each person could have a tank to hold his share of water, the tank would be half a mile on each side. If each person’s tank were to be filled from a mixture of sea water, river water, lake water, melted glaciers, and underground water, it would be almost as salty as the ocean itself for 88 percent of all water comes from the ocean basins and would dominate the mixture. So we see that water supply is not a problem of total-at least not for a long time-but of water suitable for various needs and available for use.

Moreover, fresh water has a thousand uses. Water is needed for drinking, for washing, for plumbing, for air-conditioning, for swimming pools, for irrigation, for industry, for boating and fishing and swimming, for pure scenic enjoyment, for transportation, and for the raising of food of any kind. For each use the water requirements differ and for each type of water the supply varies.

Drinking water, if it is to be used continuously with no harmful effects, must fulfill a great number of requirements. It cannot even be perfectly pure, for many of the elements needed for good health come from the dissolved minerals in drinking water. If only pure water is drunk it acts somewhat like a leaching agent and robs the body of essential salts as it passes through our systems. Nor can it contain more than about one tenth of one percent dissolved minerals before it develops a strong, unpleasant taste, and begins to upset digestion.

We are the most complex water treatment factories that can be imagined, taking in enormous quantities of water, extracting and using the elements we need, then expelling them in many ways: through skin, kidneys, intestines, through mouths and noses. When the chemical elements are taken in they are segregated appropriately into the different body fluids and sent on to perform their proper functions. Calcium, strontium, and phosphorus are sent to the bones, potassium is enriched many times within cells, iron goes into red blood cells. The human factory is pretty well geared to a diet of average stream water, but despite the flexibility of the system, a marked increase of almost any element in the water supply causes impairment of the functions of the factory. The dynamic and current nature of the human factory is almost unbelievable. If a person is completely immobilized, he begins to excrete more calcium than is taken in. His bones literally begin to dissolve and do it so fast that the calcium cannot be excreted fast enough to prevent its climbing to dangerous levels in the blood. Astronauts exercise regularly in flight; one of the reasons is to prevent calcium toxemia, as it is called.

“Average” drinking water contains about two hundredths of one percent of dissolved minerals (the same as 200 parts of minerals in a million of water, or 200 ppm). A quart boiled to dryness leaves only about one two-hundredth of an ounce of solid residue behind. This residue is made up mostly of three “salts”: common salt (sodium chloride), limestone (calcium carbonate), and gypsum (calcium sulfate), plus some silica (silicon oxide). There are traces of magnesium and potassium salts as well, and miniscule amounts of almost every other element known.

The proportions of the three chief salts differ markedly from place to place; water reflects the compositions of the rocks and soils through or over which it has passed, collecting dissolved minerals as it goes. High sodium and chloride and calcium have little influence on the taste of water, but when the sulfate content goes up water takes on an unpleasant astringent quality. Often when sulfates are high, magnesium is too. Many waters in the arid and semi-arid western states contain a lot of magnesium and sulfate. The combination wreaks havoc with the intestinal tracts of tourists, commonly having a strong laxative action. But the adaptability of the human body is remarkable; natives of the magnesium-sulfate water areas accommodate so well to their drinking water that they not only live happily with it, they may complain that the waters of other places are bland and uninteresting.

It is the flexibility (within limits) of the human body that makes it difficult to say exactly which dissolved minerals and what amount in the water supplies are safe or beneficial. The U.S. Public Health Service sets up standards for the permissible amounts of the various elements in the public water supplies. The task is a continuing one, for careful long-term records are needed to know whether any given substance is good or bad. Because waters differ so much and contain so many different elements, the job of isolating the effects of a given element requires vast amounts of information about the medical histories of the inhabitants of regions served by a particular kind of water.

There are tests for toxic elements like lead and arsenic. There are tests for radioactive substances. There is a growing list of tests for new compounds like insecticides.

One of the surprising bits of information that comes from reading about the limitations of water composition for the good health of fish, for boiler feed, or for irrigation, is the relative liberality of the standards for drinking water. We seem to be more adaptable than many species of animals and plants in the range of substances we can drink and still survive in good health. We think of ourselves as being delicate; it may be that because of our adaptability we would be among the last survivors in a world of uncontrolled degeneration of water quality.

But no matter what our intake of water we all need a minimum amount for survival. We can go for perhaps eighty days without food, but only ten days without water. A 1 or 2 percent variation in body water is painful; with a loss of 5 percent the skin shrinks, the mouth and tongue become dry and hallucination begins; a 15 percent loss is fatal. We can also have too much water, causing nausea, weakness, mental confusion, disorientation, convulsions and even death.

The body regulates itself quite well and keeps a remarkably constant composition, 70 percent of which is water.