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<br />292J
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<br />xvii
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<br />In addition to ct:.her benefits that "ill accrue from construction of Narrows
<br />Reservoir, incidental be~efits ,ull result from control of sediment, especially
<br />that sediment originating on Bijou Creek. Bijou Creek carried a breat amount of
<br />sediment during infrequent floods on that stream. Experience has taught irrigators
<br />below the mouth of Bijou Creek to cease diversion of water during periods when
<br />large amounts of Bijou Creek sediments are in the river, as it appears that Bijou
<br />Creek sediments are composed largely of inert material which forms a harmful crust
<br />on the land.
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<br />All sediment carried by the South Platte River, Bijou Creek, and Kiovla Creek
<br />will flow into da,'ro\'rs Reservoir. The average annual sediment load computed to
<br />flow into Narrows heservoir is 1,500 acre-feet, of r.hich the bouth Platte j(iver
<br />contributes 310 acre-feet; Kiowa Creek, 290 acre-feet; and Bijou Creek, 900 acre-
<br />feet.
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<br />In simulated operation and utilization studies of the Narrows Reservoir, only
<br />75,000 acre-feet of sediment were considered since this is the ~uantity that would
<br />be deposited during a normal repayment period of 50 years. H01rever, by expansion
<br />of the spillllay capacity and reallocation of storage space, it -,muld be possible to
<br />store 150,000 acre-feet in 100 years of sedimentation without encroachment on the
<br />conservation pool.
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<br />Method of Operation
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<br />Operation criteria for the Harrows l1eservoir were established: which would
<br />provide maximum benefits and utilization of the available water supply consistent
<br />with incidental uses of btate laws and the South l'latte !liver compact. Article 19
<br />of the Contract betnoen the United States and the ;'Jor'ohern Colorado Water Conserv-
<br />ancy District contains a section pertaining to retur,; :::'ao:rs. This article states,
<br />in effect, that the i;orthern Colorado \'Iater Conser-.-:: ::. :;:.strict, throug!l the con-
<br />tract with the United :,tates, I:as the right to rot'""" .:-:'o:':s accruing to the river
<br />f)Com the Colorado River Basin by the Colorado-Big Ti,c".)~on !'roject. Initial appli-
<br />cation of the supply to irrigation and municifal uses will, with very few exceptions,
<br />be applied to lands above Kersey, Colorado. Distribution of the linported supply
<br />ttJ water users is based on the contract between i.ndividual users and, the Conservancy
<br />D',stric't. In all studies of water available for storage in J'Jari'ows nese~oir, it
<br />h;8, ')een consie,ered 'that return flows made available as a result of Lllportations
<br />ir.to the basin ~,:;,mot be identified as specifically originating as trans-mountain
<br />dh3.siona and, nence, are e part of the streamflows available for use by appropria..
<br />t"I"J of th."J water with distrihution according to priorities, The only water con-
<br />sit:3red storable in j;arrows is tl'"'t to which Na-:,rows would be entitled by virtue
<br />of the priority of any right which might be acquired fer it.
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<br />Following completion of the Narrows Dam, there will be two main operating con-
<br />ditjons <;xperie:nce:d: one, an inter"cl11 condition, which will preva,il unV.l such time
<br />a5 p.)tenti"l transmountain diversion projects a"("e developed and re~urn flows from
<br />tht-:.;3B tl'd..l",;:':iilountain di '.rerSi0:1S be,;oine available j seco:lc, th~ ul ti.-na te co~di tion,
<br />whi.,c;h wi:::C be experien"ed fllter r6cnrn f101'rs f"("o')ffi poter.tial '~pstrec.m c;e\'21opTI8nt be-
<br />C"'l'." aV2,L.,."tle. The main differen':e is that Wld0r the interim conuitio!l w!len only
<br />tAle Color.'l,~o-Big Thornpso!l !Toject is in operati.on there is only safficient water on
<br />the average to furnish sup~lenental vrater to 230,000 acres of currently irrigated
<br />1an~. Thg re~idual shorc~ge remaining after direct use of these return flovffl can
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