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Appendix C Glossary ACRE-FOOT A traditional measure of water applied, used in the United States. The volume of water required to cover 1 acre of land to a depth of 1 foot. Equal to 1.2 megaliters (ML) or 1,233.5 cubic meters (my. ANADROMOUS Fish species that ascend rivers from the sea to breed. APPROPRIATION DOCTRINE The system of water law dominant in the western United States under which (1) the right to water was acquired by divert- ing water and applying it to a beneficial use and (2) a right to water acquired earlier in time is superior to a similar right acquired later in time. Also called prior appropriation doctrine. In most states, rights are not now acquired by diverting water and applying it to a beneficial use. Such a system is referred to as the constitutional method of appropriation. Rights are acquired by application, permit, and license, which may not require diversion and application to a benefi- cial use. Superiority of right is based on earliest in time and has no reference to whether two rights are for a similar use. AQUIFER A formation, group of formations, or part of a formation that con- tains sufficient saturated permeable material to yield significant quantities of water to wells and springs. BENEFICIAL USE A use of water resulting in appreciable gain or benefit to the user, consistent with state law, which varies from one state to another. CENTER PIVOT IRRIGATION An irrigation system that pumps ground water from a well in the center of a field through a long pipe, elevated on wheels, that pivots around the well and irrigates the field in a large circular pattern. CONSUMPTIVE USE Use of water that renders it no longer available be- cause it has been evaporated, transpired by plants, incorporated into products or 190

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APPENDIX C 191 crops, consumed by people or livestock, or otherwise removed from water sup- plies. DEPLETION Net rate of water use from a stream or ground water aquifer for beneficial and nonbeneficial uses. For irrigation or municipal uses, the depletion is the headgate or wellhead diversion minus return flow to the same stream or ground water aquifer. DIVERSION A turning aside or alternation of the natural course of a flow of water, normally considered physically to leave the natural channel. In some states, this may be a consumptive use direct from a stream, such as by livestock watering. In other states, a diversion must consist of such actions as taking water through a canal, pipe, or conduit. DRIP IRRIGATION A form of microirrigation. EVAPOTRANSPIRATION The sum of evaporation and transpiration from a unit land area. Also see consumptive use. FLOOD IRRIGATION A surface irrigation system where water is applied to the entire surface of the soil so it is covered by a sheet of water; called "controlled flooding" when water is impounded or the flow is directed by border dikes, ridges, or ditches. FURROW IRRIGATION A surface irrigation system where water is directed down furrows between rows of crops. Common for annual row crops, trees, and vines. GROUND WATER OVERDRAFT (MINING) The withdrawal of ground water through wells, resulting in a lowering of the ground water table at a rate faster than the rate at which the ground water table can be recharged. HIGH-VALUE CROPS (SPECIALTY CROPS) Crops with a limited num- ber of producers and demand or those with high per acre production costs and value. Examples include most fruit and vegetable crops, ornamentals, green- house crops, spices, and low-volume crops such as artichokes. INPUTS Items purchased to carry out a farm's operation, such as fertilizers, pesticides, seed, fuel, and animal feeds and drugs. INSTREAM USE Any use of water that does not require diversion or with- drawal from the natural watercourse, including in-place uses such as navigation and recreation. IRRIGATION The application of water to soil for crop production or for turf, shrubbery, or wildlife food and habitat. Intended to provide water requirements of plants not satisfied by rainfall. IRRIGATION DISTRICT In the United States, a cooperative, self-governing public corporation set up as a subdivision of the state, with definite geographic boundaries, organized to obtain and distribute water for irrigation of lands within the district; created under authority of the state legislature with the consent of a designated fraction of the landowners and having taxing power. IRRIGATION EFFICIENCY Ratio of irrigation water used in evapotranspi

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92 APPENDIX C ration to the water applied or delivered to a field or farm. This is one of several indices used to compare irrigation systems and to evaluate practices. IRRIGATION FREQUENCY Time interval between irrigations. IRRIGATION RETURN FLOW The part of applied water that is not con- sumed by evapotranspiration and that migrates to an aquifer or surface water body. See also return flow. IRRIGATION WATER REQUIREMENT The quantity, or depth, of water, in addition to precipitation, required to obtain desired crop yield and to maintain a salt balance in the plant root zone. IRRIGATION WITHDRAWALS Withdrawal of water for application on land to assist in the growing of crops and pastures or to maintain recreational lands or landscaping. LAND LEVELING Earth moving done on irrigated fields to improve surface slope and smoothness to facilitate water application. Land leveling, which can include laser leveling, can produce uniform slopes in the direction of irrigation- stream advance and may improve conditions for salinity control by improving uniformity of surface irrigation. MEGALITER A measure of volume: 1 ML equals 0.8107 acre-foot; 1 acre- foot equals 1.23 ML and is the volume of water required to cover 1 acre of land to a depth of 1 foot. MICROIRRIGATION Irrigation methods such as drip/trickle, subsurface, bubbler, and spray irrigation. In microirrigation systems, water usually is deliv- ered to the soil near the plants through a network of tubing with closely spaced, low-flow rate emitters. Water typically infiltrates where applied, and the soil volume wetted is therefore controlled by the number of application points and the lateral movement of water in the soil. Systems of emitters are easily automated, making frequent, light water applications possible without high labor costs. A high level of management is needed. NET DEPLETION Total water consumed by irrigation, or other use in an area, equal to water withdrawn minus return flow. PHREATOPHYTE A deep-rooted plant that obtains its water from the water table or the layer of soil just above it. PRIOR APPROPRIATION A concept in water law under which a right is determined by such a procedure as having the earliest priority date. PUBLIC INTEREST An interest or benefit accruing to society generally, rather than to any individuals or groups of individuals in the society. PUBLIC TRUST DOCTRINE A poorly defined judicial doctrine under which the state holds its navigable waters and underlying beds in trust for the public and is required or authorized to protect the public interest in such waters. All water rights issued by the state are subject to the overriding interest of the public and the exercise of the public trust by state administrative agencies. REACH A specified length of a stream or channel. RETURN FLOW The amount of water that reaches a ground or surface water .

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APPENDIX C 193 source after release from the point of use and thus becomes available for further use. See also irrigation return flow. RIPARIAN Relating to or living or located on the bank of a natural water- course, usually rivers but sometimes lakes or tidewaters. RIPARIAN RIGHTS A concept of water law under which authorization to use water in a stream is based on ownership of the land adjacent to the stream and normally not lost if not used. RUNOFF That part of the precipitation that moves from the land to surface water bodies. SALINIZATION To become impregnated with salt; concentration of dissolved salts in water or soil water. An environmental impact of irrigation that can be managed but not eliminated. SPRINKLER IRRIGATION Sprinkler irrigation systems can be either set or mobile. In set systems, the sprinkler heads are stationary while applying water. Mobile systems move continuously, either in straight lines or circular patterns while irrigating; these generally cost more than set systems but require less labor. TRANSFER (CONVEYANCE OF WATER RIGHT) A passing or convey- ance of title to a water right; a permanent assignment as opposed to a temporary lease or disposal of water. WATERSHED A geographic region (area of land) within which precipitation drains into a particular river, drainage system, or body of water that has one specific delivery point. WATER USE EFFICIENCY Marketable crop production per unit of water consumed in evapotranspiration. WATER WITHDRAWAL Water removed from ground or surface water sources for use.

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