What Kind of Water Supply is Needed.—The quality of a water supply is even more important than its quantity. For that reason every up-to-date city employs skilled engineers not only to determine the best source of water and how it shall be protected from contam ination, but also to construct purifying works if necessary and to test the water continually, to see whether it contains any harmful impuri ties. The requisites of a good water supply are as follows: (1) Freedom from Mud.—Mud is a comparatively common evil, but does little harm. The people of St. Louis, for example, drink the muddy water of the Mississippi River. Now they filter it, but even before they had their great filtration plants, they found it whole some. A little mud is harmful chiefly because it does not look attrac tive, and it is largely for this reason that cities build settling basins where the water stands still for some hours and drops its load of silt. In some cases, however, even a prolonged period of quiet will not cause the finest clay to settle, and some of the most wholesome water sup plies are a little cloudy.
(2) Freedom from Taste and Smell.—Water that has a disagree able taste or especially a distinct smell is undesirable. Often, how ever, what people call a disagreeable taste means merely a taste different from that to which they are accustomed. A smell is more likely to be a sign that something is really wrong. Yet neither taste nor smell necessarily indicates that the water is unwholesome, as many people in prairie towns are well aware. Nevertheless, since both are disagreeable, and since either may indicate that the water is bad, cities go to great expense in order to get rid of them, either by filtration or by chemical treatment.
(3) Freedom from Chemical Impurities.—Some chemical impuri ties reveal themselves by their taste or smell. A large number, how ever, such as the lime which causes hardness, do not make the water disagreeable, while some—such as iron—which produce both taste and smell, are beneficial. Lime is by far the most harmful of the com mon chemical impurities of water and the hardest to get rid of. When hard water is used in boilers it causes the deposition of a limy cake on the inside of the boiler and soon ruins it. In the same way, in man's body, it may increase the susceptibility to rheumatism, goiter, and other diseases. Yet such water may be sparkling and clear, without odor, and with the most delightful taste.
(4) Freedom from Bacteria.—This is by far the most important quality of a water supply. Water that is ideal in other respects may contain the germs of typhoid fever, dysentery, and other diseases. The city of Niagara Falls has suffered greatly from typhoid because Buffalo discharges its sewage into Lake Erie and Niagara Falls takes its water from the Niagara River which flows from that lake. Even though the water seems to have become perfectly clear and has no mud, no taste, no odor, and no chemical impurities, the disease germs of Buffalo still live and do vast harm. In Europe the prevalence of
typhoid germs in the water supply of many of the cities is one chief reason why wine and beer are used so extensively. In China, where disease germs are still more abundant in the water, the people almost universally drink tea. They have found by long experience that the best way to get rid of bacteria is to boil the water, a lesson which people ought to remember when obliged to use doubtful supplies of water or when typhoid and dysentery are common.
How a Water Supply is Procured and Distributed.—(1) Primitive Methods.—The simplest way of getting a supply of water is to dip it up by hand from a stream, spring, or lake. In Oriental countries like Persia, and in tropical countries like India and Venezuela, one can any day see scores of women walking gracefully to the stream or the fountain with earthenware jars poised on their heads or shoul ders. Elsewhere men with plump goatskin bags on their backs or driving barrel-shaped little donkey carts bring water from the muddy river and fill the big earthenware pots that stand in a shady corner of every courtyard.
(2) Ordinary Wells.—Among civilized people and among many who are only partly civilized, wells are the most common source of water. This is because the soil and the solid rock are everywhere saturated with water below a certain depth. The varying level at which permanent water is found is called the water table. The water table is only a few inches below the surface in swamps, but generally several hundred feet in deserts. Wherever a well is sunk it must go deep enough to penetrate below the lowest level to which this table falls in dry seasons. The chief difficulty with wells is to raise the water to the surface. In many places this is done by hand with long ropes. In parts of tropical Mexico long lines of women come to the wells in the cool of the morning long before sunrise and wait their turn in order to pull up water from a depth of a hundred feet or more. Often, how ever, this work is done by horses, oxen, or camels. In Mexico the well rope is sometimes fastened to the horns of an ox, or to the saddle of a horse, where it causes a great and unnecessary strain which soon kills the animals. These primitive methods, however, are fast being replaced by machinery. The simplest machine for drawing water is the hand pump, but pumps run by animal power, by wind, and by gasoline are also largely used. The use of such power pumps usually leads to the building of tanks or reservoirs, and thus makes it easy to have running water in the house at all times. This is a great advan tage, for the easier it is to get water the more likely people are to use it, not only for drinking and cooking, but also for bathing, washing, and fire protection. Moreover, such a water system is a great help in insuring purity.