Oceanography

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.