Volume III - Nos. 4 & 5
A safe, adequately distributed water supply, upon which a park of any mentionable proportions must depend for its very existence, usually is taken for granted by the casual visitor. In defense of those to whom it is a major and sometimes extremely troublesome problem, the following brief outline of a few of the considerations involved in water supply development is offered with the hope either of enlightening the reader of or confusing him to the point of regarding engineers as members of a profession rather than as sly wielders of magical divining wands.
Since human beings are prone to certain gullibility --- and to travel about the country with scanty laboratory equipment --- they are likely to drink water issuing from almost any spigot or fountain without knowing at all whether it is good for man or beast. In order to reduce the mortality which would result from promiscuous water drinking, the various cities, counties, states, and even the federal government, assisted by interested societies, have passed laws making it the responsibility of the dispenser of water to see to it that it is safe, regardless of how it may taste. Making it look and taste good is where artistry is sometimes required.
Meteoric water is, of course, the source of all water whether it is found on the earth as surface water or as ground water. Chemically pure water is not to be found in nature, and that is just as well, for water which contains certain salts is more palatable and better suited to general use than that which has been distilled. Watery vapor condensed in the air as rain or snow absorbs impurities from the atmosphere. Gases normally present in the air, such as nitrogen, oxygen and carbon dioxide, also are absorbed, while ammonia, sulphuric acid and nitrous and nitric acids likewise are found. Rain water is deficient in minerals, however, and it therefore is "soft." Rain or snow takes up germ life from the air, the concentration of such organisms varying with the duration of rain fall and with the altitude. (The higher concentrations occur during the earlier periods of a storm and at the lower altitudes.)
The history of water from the time it is precipitated until it finds its way back into the air is marked by the absorption of various substances, some carried in solution and others in suspension. As a result of chemical reactions some of these ingredients subsequently are precipitated or eliminated. Unfortunately, some of the changes are undesirable from the standpoint of the prospective consumer.
When meteoric water comes in contact with the surface of the earth it absorbs contamination, pollution and even infection, and as it passes through the soil or rock formations it absorbs minerals. It thus is evident that the course of its travel has a good deal to do with the quality of any water.
The sources of water are numerous. They are divided into the two general classifications of surface and ground waters. For convenience surface waters may be considered under the headings of rain, streams, natural lakes, and artificial lakes, all of which present problems of collection and treatment peculiar to themselves. Ground water may be divided into the four categories of springs, shallow wells, deep and artesian wells, and water from horizontal galleries.
Generally speaking, surface waters, in addition to being more liable to pollution, are subject to changes of character as a result of climatic disturbances, and their satisfactory treatment frequently requires closer surveillance than do ground waters. Ground water obtained from properly protected and developed springs or wells, with the exception of those fed from cavernous formations, are generally more constant in temperature and more stable in character. For reasons outlined above, as well as others which will not be discussed here, it is nearly always desirable in developing a small water supply to exhaust first the possibility of obtaining a suitable ground water source before resorting to the treatment of surface water.
It is not true that all surface waters present serious complications in their treatment for domestic use, or that all ground waters may be easily rendered satisfactory. It is true, however, that ground waters obtained from a suitable horizon and which have been properly developed are less subject to physical or chemical change and therefore may be more safely used for a domestic supply under lay supervision.
Such great strides have been made in the treatment of water that the feasibility of installing adequate equipment is too frequently taken for granted in park work. The difficulties encountered in attempting to treat water for park use are a result of the small scale of the operation and it is the writer's recommendation that unless it can be treated by mere slow sand filtration, or by sterilization, or by a combination of the two, the development should be abandoned as far as its dependence upon a safe supply is concerned. This seemingly drastic recommendation has for its foundation the following reasons:
Where the treatment of water is dependent upon the use of chemicals and accurate rate control, proper operation is contingent on constant observation and occasional alterations in the chemical dosage to compensate for changes in the character of the raw water. It may be readily seen that as the size of the plant is reduced the more sensitive it becomes to small alterations in chemical dosage and the greater the skill required by the operator to produce the desired result. It should not be necessary to point out the unsoundness of investing heavily in water treatment equipment unless the benefits thereof are to be derived. It therefore follows that where water is to be treated by one of the more complicated methods the constant expense of a skilled operator must be considered a prerequisite to the desired results.
The question of a safe source of supply is only one of the many vexatious water problems which must be solved and, for the most part, buried under the ground before the take-it-for-granted park visitor can find it possible to perform the simple act of taking a drink of water with impunity. If this brief discussion achieves no purpose other than to impress its readers with the advisability of not only consulting competent engineers and geologists when necessary, but also of following their recommendations, it may have served a useful end.
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