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FACTORS GOVERNING THE SELECTION AND PROTECTION OF SOURCES OF WATER SUPPLY.

A wholesome, ample, and satisfactory supply of water is one of the fundamental needs of any community, regardless of its size, and, therefore, the selection of the source of a supply having these quali-. ties is a problem that has been solved or must be solved by every group of individuals forming a community, regardless of whether this group be the isolated family or the large city. The degree of success attained in the handling of this problem is quite closely related to the comfort, well being, and health of the community.

There are certain factors that must be taken into consideration in the selection of a suitable source of water supply, and these various factors must be carefully weighed in the light of local requirements. in order that that source may be chosen which most nearly meets the local needs. No absolute rules can be laid down for universal adoption, but general principles can be stated which, through long experience, have been found to be of value in reaching a wise decision. The following are some of the factors that must be considered: the nature and extent of use of the contemplated supply; the sources available; the quantity of water available; the quality of available supplies; the possibilities of pollution of the supply; the natural safeguards that may be employed for protecting the supply; and the cost of installation and operation of the system.

Nature and Extent of Use.

The nature and extent of use of a contemplated water supply will often determine the choice of a source. If water is to be used for industrial purposes, such as boiler feed water or for the washing of white paper stock, evidently the qualities required would be different from those necessary in a water used for cooling or condensing purposes or for fire protection. If the supply is to be used for drinking and other domestic purposes, then other qualities are requisite, such as freedom from disease organisms, qualities not essential to a strictly industrial supply.

For obvious reasons the extent of use must be known. A small mountain stream might readily supply a village but be entirely inadequate for a growing city; or a well might be of ample capacity for one industry but totally unable to supply a community. The ultimate yield of any prospective source must always be considered and reasonable assurance obtained that it will always exceed the maximum anticipated demand.

FACTORS GOVERNING THE SELECTION AND PROTECTION OF SOURCES OF WATER SUPPLY.

A wholesome, ample, and satisfactory supply of water is one of the fundamental needs of any community, regardless of its size, and, therefore, the selection of the source of a supply having these quali-. ties is a problem that has been solved or must be solved by every group of individuals forming a community, regardless of whether this group be the isolated family or the large city. The degree of success attained in the handling of this problem is quite closely related to the comfort, well being, and health of the community.

There are certain factors that must be taken into consideration in the selection of a suitable source of water supply, and these various factors must be carefully weighed in the light of local requirements in order that that source may be chosen which most nearly meets the local needs. No absolute rules can be laid down for universal adoption, but general principles can be stated which, through long experience, have been found to be of value in reaching a wise decision. The following are some of the factors that must be considered: the nature and extent of use of the contemplated supply; the sources available; the quantity of water available; the quality of available supplies; the possibilities of pollution of the supply; the natural safeguards that may be employed for protecting the supply; and the cost of installation and operation of the system.

Nature and Extent of Use.

The nature and extent of use of a contemplated water supply will often determine the choice of a source. If water is to be used for industrial purposes, such as boiler feed water or for the washing of white paper stock, evidently the qualities required would be different from those necessary in a water used for cooling or condensing purposes or for fire protection. If the supply is to be used for drinking and other domestic purposes, then other qualities are requisite, such as freedom from disease organisms, qualities not essential to a strictly industrial supply.

For obvious reasons the extent of use must be known. A small mountain stream might readily supply a village but be entirely inadequate for a growing city; or a well might be of ample capacity for one industry but totally unable to supply a community. The ultimate yield of any prospective source must always be considered and reasonable assurance obtained that it will always exceed the maximum anticipated demand.

Sources of Supply.

After the nature and extent of use are determined, the selection of a source will evidently be somewhat restricted. It may be well, therefore, to discuss the various sources of water so that all available supplies may be given consideration.

Primarily, all available water is of meteoric origin. Water is evaporated from the ocean and surface of the earth, is condensed and falls as rain, and then flows, either on the surface or underground. from higher to lower levels until the ocean is again reached, thus completing the cycle. It is therefore necessary to obtain a supply from some source within this cycle. Since the collection of falling rain water is expensive and difficult, although often resorted to by individual families, the remaining sources, surface and undergroun waters, are usually those generally considered.

Collection of rain water is usually feasible only for restricted use, such as for individual families, because of the necessary surface required for such collection. Roofs are the most common collecting surface used, and the water draining therefrom is stored in various ways. Such storage should not be exposed to light because of the rapid development, under such conditions, of various organisms and plant life that will impart disagreeable odors and tastes to the stored water.

Surface water may be secured either from flowing streams or from natural lakes. Water may be pumped directly from streams or it may be diverted into impounding or storage reservoirs and drawn from them. Lakes are usually of the nature of natural impounding reservoirs, and supplies of water are frequently drawn directly from them. Owing to the necessary contact with the surface of the earth and the existing polluting conditions thus encountered, surface waters contain varying amounts of dissolved and suspended foreign matters that often render the supply objectionable and even unsafe. That portion of the rain water falling on the earth that percolates through the surface layers and fills the interstices of the porous material encountered, is referred to as underground water. Owing to the close contact of such waters with the earth, ground waters frequently carry in solution considerable quantities of mineral substances, such as iron, salt, sulphur, limestone, etc. Cround waters may be collected by means of wells reaching into the submerged strata, by springs, or by horizontal or inclined collecting galleries channeled or driven so as to intercept or divert the natural underground flow.

Wells are of three general types: shallow, deep, and artesian. Shallow wells are what the name implies and draw their supply from ground-water storage of the surface earth layers. They are therefore frequently subject to gross contamination, and for this reason their use for domestic supply in urban communities is usually prohibited.

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