Sources Of Water

Surface Water Surface water supplies are obtained from streams, rivers, lakes, and reservoirs. The quantity of water available from a surface supply can be determined with reasonable accuracy from yield studies that take into account the local effects of rainfall, runoff, evaporation and sedimentation rates, and other hydrological factors. Development of a surface supply usually requires pumps to transport raw water from the source to a treatment plant and to provide the head necessary for proper hydraulic operation of the treating facilities. Pumps utilized for this purpose are classified as low-lift pumps because relatively low discharge heads are required.

Selection of a specific type of pump for low-lift service is dependent on intake conditions. Because surface water supplies vary significantly in temperature, bacteria count, and turbidity at varying depths and because the water level may fluctuate considerably, it is necessary to provide some type of intake structure that will permit withdrawal of water at several elevations. Multiple intake ports equipped with trash racks and water screens provide this capability and provide protection from fish and debris. The design and location of the intake structure influence the selection of either a horizontal or vertical pump for low-lift service.

Groundwater In many areas of the United States where rainfall and runoff are sparse, significant supplies of water are available from underground sources. The groundwater table is formed when rainfall percolates through the soil and reaches a zone of saturation, the depth of which is governed by soil characteristics and subsurface conditions.

Groundwater can be developed as a source of supply through utilization of wells or springs. Shallow wells generally utilize the water table as a source, whereas deep wells

utilize water held in a pervious subsurface stratum (aquifer). Deep wells generally provide more constant and more prolific supplies than do shallow wells.

Artesian wells may be developed when an aquifer outcrops at a surface elevation significantly higher than the ground elevation at the well site. The aquifer is thus pressurized, and water flows from the well without pumpage. A natural artesian well may occur if a fault extends from the aquifer to the ground surface.

Springs occur where the groundwater table outcrops at the surface of the earth. However, the supply available from springs is seldom great enough to serve more than one or two homesteads and is thus usually insignificant in terms of supplying communities. Surface streams may also be fed from the groundwater table, and vice versa. Figure 1 depicts these various conditions.

Well water is usually pumped to a treatment site or into a distribution system by either vertical turbine line shaft pumps or submersible pumps. Economics dictates the selection of one type over the other. In general, at depths greater than 500 ft (150 m) submersible pumps become economically competitive with line shaft pumps. For shallower depths, line shaft pumps are used almost exclusively.

Effects of Source on Water Quality Although the quality of water obtained from both groundwater and surface supplies varies greatly according to local climatological, hydro-logical, and geological conditions, some general comparisons can be made between ground-water and surface supplies. Surface supplies generally contain more bacteria, algae, and suspended solids than do groundwater sources and thus require specific treatment to eliminate the resulting turbidity, colors, odors, and tastes.

Groundwater supplies generally contain few bacteria and in some instances are pure enough for domestic use without chemical treatment. Frequently, however, groundwater supplies contain significant amounts of dissolved minerals. Depending upon the mineral type, the resulting supply may exhibit such characteristics as extreme hardness, toxicity, or undesirable color, odor, or taste. Special treatment such as aeration, lime softening, and disinfection may be required to remove such objectionable characteristics.

Survival Treasure

Survival Treasure

This is a collection of 3 guides all about survival. Within this collection you find the following titles: Outdoor Survival Skills, Survival Basics and The Wilderness Survival Guide.

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