The quality of water is the ability of water to be potable and palatable (water that is safe to drink, being free of harmful characteristics that could cause odor, foul taste, bad color and/or disease).
Practically all water supplies have been exposed to pollution of some kind. The general growth of population and the increasing use of streams and other bodies of surface water for the disposal of wastes have been detrimental to water sources.
Impurities in water are either suspended or dissolved. The suspended impurities are usually more dangerous to health. They include mineral matter, disease organisms, silt, bacteria, and algae. These must be destroyed or removed from water that is to be consumed. While some of these impurities can be seen by the naked eye, others
Table 9-2.-Quantity and Quality of Water Needed by Construction Equipment
can be detected by laboratory tests only. Table 9-3 identifies some of the common impurities in water and summarizes their effect on water quality.
Water samples must be forwarded to a laboratory for complete mineral or bacteriological analysis.
The factors that affect and determine the quality of water, such as physical, chemical, biological, and radiological contamination, are discussed later in this chapter.
The reliability of a water supply is one of the most important factors in the selection of
a water source. The information gathered during the water reconnaissance may indicate a source of sufficient supply only to have the source dry up during periods of no rainfall. Study the hydrological data to determine the variations that may be expected at the water source.
Geological formations influence the reliability of a groundwater source. The amount of water flowing and the rate of flow maybe controlled by geological layers. The amount of water within a water table may be limited by impervious formations, as shown in figure 9-4. Therefore, it is important that information on the characteristics and properties of the geological formations be studied when a ground source is being considered.
Table 9-3.-Common Impurities in Water
It may be necessary to consider numerous other factors that may affect the reliability of the source. For one example; Lake Bonnie Rose, U.S. Naval Station, Adak, Alaska, is an ample source of cool, clear water, being distributed by gravity. However, the relatively high elevation of the lake results in excessive pressure at the station. Pressures are controlled by pressure-reducing valves. The valves sometimes fail in service, resulting in damage to the water system.
Reliability of the source is further increased as the requirements for items that are subject to breakdown decrease (pumps, treatment plants, and so on).
Legal advice may be necessary when selecting a water source as the laws regulating and controlling water rights may vary considerably. The title to ground and surface water in the United States is usually regulated at the state level. Navigable waters having interstate traffic are under federal control. Some difficulty was experienced in Vietnam by SEABEES in securing water rights to surface streams. These waters were used for flooding of rice fields, and local control denied the use of these sources as water supplies.
Legal advice may also be required in securing the right for waterlines or powerlines to cross property. To cite one example, a waterline serving a naval air facility in Sicily was completed, except for a section crossing an irrigation ditch. Final completion of the waterline was delayed for
Figure 9-4.-Limitation of water by rock formation.
2 months, waiting to obtain the right for the waterline to cross the ditch.