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<br />1 <br /> <br />, <br />. <br /> <br />. <br /> <br />.. <br /> <br />- <br />1 <br /> <br />I <br /> <br />economic iife of a reservoir.--In project planning, a feasibility study is <br />made for any proposed reservoir. As a part of this study, consideration is <br />given to the decrease of storage space .within the reservoir by the deposition <br />of sediment. The determination must be made that, during some period, the <br />economic life of the reservoir, the economic benefits derived from storage in <br />the reservoir, or flood protection by the reservoir are greater than the cost <br />of constructing and maintaining the reservoir. The "useful life" of the <br />reservoir usually extends far past the economic life. <br /> <br />evaporation charge.--If evaporation from the water surface of an on-channel <br />reservoir were not accounted for, would constitute a loss to the stream on <br />which the reservoir is built. To offset this loss of public waters. the daily <br />rate of evaporation is measured (usually by a class A pan): a pan factor is <br />applied to convert pan evaporation to lake-surface evaporation, and this rate <br />is applied to that day's lake-surface area to compute the day's evaporation. <br />Allowance is made for the evaporation that would have taken place had the lake <br />not been present, and the resulting volume is released to the river from the <br />storage account occupying the lake. The evaporation charge is administered in <br />the Arkansas River basin by the Division Engineer, Colorado Water Division 2. <br /> <br />exchange.--A water exchange is possible by diverting water at one point in the <br />river system, and replacing a like quantity of water from storage or trans- <br />mountain diversions at another point in the system. To be legal, no party can <br />be injured by the diversion. For example, an exchange is made to enable use <br />of Lake Meredith water by irrigators who have rights to water diverted by the <br />Colorado' Canal. As Lake Meredith is downgrade from most land irrigated by <br />water diverted by the canal, water is diverted from the river at the Colorado <br />Canal headgate, and replaced, made whole, from storage through the Meredith <br />Outlet Canal, which enters the river a few miles downstream from the headgate. <br />Sufficent flow must be left in the river downstream from the Colorado Canal <br />headgate to satisfy any senior rights between the headgate and the outlet <br />canal. Exchanges can be made upstream or downstream from the point of use. <br />River-transit losses are accounted for in the exchange. <br /> <br />flood-control pool.--See reservoir-space allocation. <br /> <br />flood right.--Said of a very junior right, one that is in priority only during <br />flooding or during a free river. <br /> <br />free river.--A local term used to describe a condition where the flow of the <br />river is sufficient to satisfy all v~sted rights, and diversions from the <br />river can be made without possibility of injury to any senior right. In the <br />Arkansas River basin in Colorado, this condition seldom exists, except during <br />fl ood ing . <br /> <br />futile call.--If, in the op1n10n of the Division Engineer, there is no <br />possibility that water called out by a downstream senior right will reach the <br />headgate of that right, the Division Engineer has the discretion (on the basis <br />of paragraph 37-92-502(2) of the Water Right Determination and Administrtion <br />Act of 1969) of not honoring the call and allowing the upstream junior right <br />to continue diversion. <br /> <br />vii <br />