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Water Use Concepts and Terms
- Water Use
- in the broadest sense, pertains to the interaction of human activity with and its influence on the hydrologic cycle and includes elements such as self-supplied withdrawal, public-supply delivery, consumptive use, wastewater release, reclaimed wastewater, return flow, and instream use. In a restrictive sense, water use refers to water that is actually used for a specific purpose, such as for domestic use, irrigation, or industrial processing. Water use is divided into two types, offstream and instream use.
- Offstream water use
- occurs when water is withdrawn or diverted from a ground- or surface-water source for public-water supply, industry, irrigation, livestock, cooling for thermoelectric power generation, mining and domestic purposes. Sometimes it is called off-channel or withdrawal use.
- The quantity of water removed from a ground-water source or diverted from a surface-water to the point of use.
- The quantity of water delivered at the point of use or treatment.
- The quantity released after use or treatment.
- The systematic and intentional movement or transfer of water from one point to another, for example, from point of withdrawal to point of delivery; release from public water supplier to user; release from user to wastewater-treatment facility; after release to return flow. Withdrawals, deliveries, releases and return flows are the endpoints of conveyances.
- Conveyance loss
- is water that is lost in transit from a pipe, canal, conduit, or ditch by leakage or evaporation. Generally the water is not available for immediate reuse; however, leakage from an irrigation ditch, for example, may percolate to a ground-water source and be available for further use.
- Consumptive use
- that part of water withdrawn that evaporates, transpires, is incorporated into products or crops, is consumed by humans or livestock, or otherwise removed from the immediate water environment.
- Return flow
- The quantity of water that is discharged after use or wastewater treatment to surface water or groundwater so that it becomes available for reuse.
- Instream water use
- occurs when the water remains in the stream (surface water) or aquifer (groundwater) during use. Instream uses include hydroelectric power generation, recreation, hydroelectric power generation, transportation, waste assimilation, aesthetics, cultural resource preservation fish and wildlife preservation, biodiversity, wetlands preservation, freshwater dilution of saline estuaries, and maintenance of the riparian zone.
- Instream conveyance
- occurs when water flows or is pumped from one reservoir to another without being used. Water may flow through a chain of reservoirs, from a river to a chain of lakes, from a river to a canal or aqueduct, or even from surface water to groundwater. In some cases, the rate of water flowing or being pumped from one reservoir to another may be reported to a State regulatory agency and should be tagged as in instream use to avoid double or triple accounting of offstream withdrawals. Quantitative estimates for most instream uses are undetermined, but are important because such uses compete with offstream uses and affect the quality and quantity of water resources.
- Public Supply
- water use includes water withdrawn from ground and surface sources by public and private water systems for use by cities, towns, rural water districts, mobile-home parks, Indian reservations, and military bases. Public-supply facilities include those providing water to at least 25 people, or a minimum of 15 connections. Water withdrawn by public suppliers may be delivered to users for domestic, commercial, industrial, and thermoelectric purposes. In addition, some public-supply water is used for water and wastewater treatment, public services such as pools, parks, and city buildings, or is lost through system leaks and maintenance. The Standard Industrial Classification code for the Public Supply category is 4941.
- Self-supplied water
- water withdrawn from a surface-water or a ground-water source by a user and not obtained from a public supply.
- water use includes water used for household purposes such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, car washing, and watering lawns and gardens. The largest components of domestic use can be inside household uses (bathing, flushing toilets, etc.) or outside household uses (lawn and garden watering, car washing, etc.) depending on the climate. The U.S. Department of Housing and Urban Development (1984) found that toilet flushing (39 percent) and bathing (30 percent) are the largest components of inside household use. Outside household uses range from near zero in humid areas to 60 percent of total domestic use in arid areas (U.S. Department of Housing and Urban Development, 1984). Domestic water may come from Public Water Supplies or be Self supplied as from a private well.
- water use is water that is applied by an irrigation system, to sustain plant growth in all agricultural and horticultural vegetation. It also includes water that is applied for pre-irrigation, frost protection, chemical application, weed control, field preparation, crop cooling, harvesting, dust suppression, and for the leaching of salts from the root zone. Non-crop activities such as irrigation of public and private golf courses, parks, nurseries, turf farms, cemeteries and other landscape-irrigation uses may all be included in the Golf-Course Irrigation subcategory.
- water use includes water associated with the production of meat, milk, poultry, eggs, and wool. The kind of stock includes dairy cows and heifers, beef cattle and calves, sheep and lambs, goats, hogs and pigs, and poultry. Poultry includes chickens, turkeys, ducks, geese, pheasants, and pigeons. Other water uses include evaporation from stock ponds, dairy and poultry sanitation or wash down, waste-disposal systems to process animal products, cooling of animals and products, and incidental water losses. Horses and other equines (SIC 0272), fur-bearing animals (SIC 0271) and Animal Specialties (SIC 0279) are part of the Livestock category. The Livestock category does not include on-farm domesticuse, lawn and garden watering, or irrigation water use.
- water use includes farming of animals that live in water, such as fish and shellfish, within a confined space and under controlled feeding, sanitation, and harvesting procedures. Includes water used by fish farms and fish hatcheries.
- water-use includes total fresh and saline withdrawals, from ground and surface sources, by businesses classified in the Standard Industrial Classification codes under Construction and Manufacturing. The Industrial water-use category includes water used to manufacture and package products, log trees and produce pulp and paper, publish written materials, refine petroleum, tan and finish leather, cut and process stone, smelt and refine metals including steel, among other things. Water used for industrial purposes may be incorporated into products or used for processing, washing, cooling, or facility restrooms and maintenance.
The five major industrial groups that use the most water per facility are:
- SIC 20 - Food and kindred products; the manufacture or processing of foods and beverages for human consumption, and related products such as ice, vegetable and animal fats and oils, and prepared feeds for animals and fowls.
- SIC 26 - Paper and allied products; the manufacture of pulps from wood and fibers; the manufacture of paper and paperboard
- SIC 28 - Chemicals and allied products; the production of chemicals and chemical products such as drugs, cosmetics, and soaps
- SIC 29 - Petroleum refining and related industries; petroleum refining and the manufacture of paving materials, roofing materials, lubricating oils and greases
- SIC 33 - Primary metals industries; smelting and refining ferrous and nonferrous metals from ore, pig, or scrap; alloying metals; manufacturing nails, spikes, and insulated wire and cable
- water use includes water that is used for the extraction of minerals, ores and gases, which may be in the form of a solid, liquid or gas. Solid minerals include coal, ores, and sand and gravel operations. Liquids pertain to crude petroleum, and gases mostly pertain to natural gas.
- Thermoelectric power
- water use is defined as the amount of water used in the process of the generation of thermoelectric power. The source of the power may be from fossil fuels, nuclear-fission, or geothermal. Water is mostly used to cool the steam water. Two general types of cooling are once-through cooling and closed-loop cooling. Water withdrawal estimates are compiled for each type of cooling system.
- Once-through cooling
- water is withdrawn from a source, circulated through the heat exchangers, and then returned to a water body at a higher temperature.
- Close-looped cooling
- uses cooling ponds and cooling towers to cool water before it is re-circulated through the cooling system.
- Units of measurement
- Water use is usually expressed as a rate, that is, a volume of water over a period of time. Common rates for water use are thousand gallons or 100 cubic feet, ccf, (as in a meter reading), gallons per minute, gpm, (as in pumpage), gallons per day, gpd, (as in per person or per household); million gallons per day, Mgal/d, (as in per facility or per geographically or politically bounded area); billion gallons per day, bgd, (as in a national total); or acre-foot, acre-ft, (more commonly used for irrigation water use and in the western United States).
- How large is a million gallons per day?
- A million gallons per day as a rate of flow of water is equal to 133,680.56 cubic feet per day, or 1.5472 cubic feet per second, or 3.0689 acre-feet per day. A flow of one million gallons per day for one year equals 1,120 acre-feet (365 million gallons).