Author
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Clemmens, Albert |
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Submitted to: Irrigation Australia
Publication Type: Proceedings Publication Acceptance Date: 5/23/2000 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, particularly as related to irrigated agriculture. When the total demand for water exceeds the available supply, as is the situation in the western United States, our ability to determine the fate of irrigation water diverted and applied becomes crucial. Measurements within these hydrologi systems are inherently inaccurate. This inaccuracy complicates precision management of water for these large-scale systems. This paper discusses application of a hydrologic water balance to such systems, in which all water entering and leaving the system is quantified. Various irrigation performance parameters, such as irrigation efficiency, are discussed and methods are presented that describe how to determine the accuracy of both water balance components and the resulting performance parameters. This approach can be useful for both individual projects and regional water management. These results should be of use to irrigation districts, consultants, and the Bureau of Reclamation. Technical Abstract: When the total demand for water exceeds the available supply, as is the situation in the western United States, our ability to determine the fate of irrigation water diverted and applied becomes crucial. On-farm water management is more concerned with the health and vigor of the crop than in whether water applied is consumed, runs off, or percolates to groundwater. However, management of the water resource requires reasonable knowledge of the ultimate fate of all water diverted. Such a water balance for an irrigated region is extremely difficult to obtain. While often the major surface inflows and outflows can be measured, many of the other inputs and outputs can be only estimated. The accuracy of these measurements and estimates becomes increasingly important as water management decisions are based on these results. In the U.S., water transfers, state water diversions, and (ultimately) water rights or duties are being influenced by ywater balances and our ability to accurately determine these water quantities. Several case studies from the southwestern U.S. are discussed in this paper. |
