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Title: WATER CONSERVATION DEFINITIONS FROM A HYDROLOGIC VIEWPOINT

Author
item ALLEN, RICHARD - UTAH STATE UNIV, LOGAN
item BURT, CHARLES - CAL POLY STATE, SLO, CA
item Clemmens, Albert
item WILLARDSON, L - UTAH STATE UNIV, LOGAN

Submitted to: North American Water and Environment Congress Proceedings
Publication Type: Proceedings
Publication Acceptance Date: 6/28/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Competition for limited water supplies has escalated substantially over the last decade. Unfortunately there are many misconceptions about water use, relating in particular to irrigated agriculture. The potential water savings that might result from increases in irrigation efficiency are usually overestimated. Many of these misconceptions and erroneous estimates of water savings stem from misunderstandings about how irrigation performance measures are defined and used. Irrigation and irrigation return flows become part of the hydrologic system, from which much of the diverted water returns to groundwater and streams downstream from its point of use. In this paper, a water balance approach (i.e., the amount of water going into a system vs. the amount of water discharged from that system) is used to distinguish beneficial uses (for defining irrigation efficiency) from consumptive uses (for identifying potential reuse). A further distinction is made to identify the reusable fraction--that part of the applied water which is reusable downstream. This simplified approach to understanding agricultural water use can be useful for regional (e.g., a river basin) water supply management.

Technical Abstract: The definition of water management principles needed to satisfy society's water use objectives requires the use of terms and definitions that clearly describe the effects of various water uses, both consumptive and nonconsumptive, within a hydrologic system. This is especially true when designing, proposing, or evaluating water conservation programs for irrigation projects. In irrigation projects where return flows conveniently reenter the fresh water resource and are of reusable quality, water is saved only over the long run through water conservation when evaporation or evapotranspiration (ET) are reduced. Some water use terms such as the evaporated fraction, reusable fraction, nonreusable fraction, and depleted fraction are discussed that can help the user and the public develop an improved, rational, and visual understanding of the hydrologic background and true impacts of water use and conservation programs.