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Show Flows are generally measured in open channels and ditches using flumes, weirs and gates. Many irrigation companies use weirs and gates to control flows to land owners. The flumes and gates are generally not equipped to record flow rates and totalize the amount of water delivered. Gates and weirs are generally set to provide a designated flow for a scheduled time during which a land owner irrigates crops. The flows and time schedules are based on water rights or shares of water stock and on irrigation demands which provide a basis for controlling or restricting water use. It is generally felt that water use by land owners ( where water is supplied by irrigation companies) rarely exceeds the water right duty approved by the state engineer. Installation of measuring devices and totalizers would be very expensive and difficult to implement. Most ditch systems are constructed such that one ditch supplies water to multiple water users. Each water user has several diversions along the same ditch through which water flows directly to crops. When the scheduled watering time is complete, the water users close their individual diversions and allow the water to continue downstream to the next scheduled water user, or upstream water users open their diversions and dam the ditch to prevent flows from continuing downstream. Often water users trade complete or partial watering schedules ( turns) with each other in order to better accommodate work, planting, spraying, harvesting and other schedules needed to meet personal and various crop water demands. Measuring devices would, therefore, need to be installed at each individual diversion to completely and accurately measure the amount of water used by each water user. The individual water users appear to monitor flows through established flow control devices and water turn scheduling. This seems, in most cases, to provide sufficient control on water use based on current water rights laws. For example, nearly all of the metering efforts in the Weber Basin Water Conservancy District are directed toward irrigation companies. Only rarely are individual customers metered. Experience indicates that conventional water meters have maintenance problems when used for agricultural water delivery. They are easily damaged by soil particles or other debris in the water. As a result, weirs or flumes are used instead of meters. Because the water allocation and costs are based on the amount of land being irrigated rather than the amount of water used, metering has little or no effect on the amount of agricultural water used ( Salter, 1995). Status Data were obtained from the 1,483 irrigation companies, water users associations, water districts and corporations that generally supply water for irrigation purposes within the state. In addition to the water companies within the state, numerous land owners use privately- owned water sources for irrigation purposes. In general, agricultural water is measured at the point of diversion specified in the water right and not at the end use. Irrigation companies generally control the amount of water use by providing headgates, weirs and other control structures that control the flow of water to the water users on each system. Water is allocated by the irrigation company based on the number of shares end users own in the irrigation company. Water users with privately- owned water sources commonly operate their own systems. Water right laws and regulations require land owners with privately- owned water sources to install meters or other measuring devices at the points of diversion. Allocations of irrigation related water rights in Utah are based on water right duties that are established by the Division of Water Rights for different areas in Utah. Historically, duties have been generally set as follows: 30 |
