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<br />..1":10<"
<br />
<br />LETTER OF TRANSMITTAL
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<br />XXI
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<br />the end of the period more than one-half of the eap'eity so allocated.
<br />In the meautime, the cltpacity of thc chltnnel will have increased,
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<br />Required re8er"o';r capacities jor jlood control
<br />Colomdo made It studv to est.imat(, the Itpproximltte amount of
<br />flood-control capacity nee,led to cont.rol the flow at Otowi to vltrying
<br />amounts, rangiug from 5,000 to 10,000 c. f. s, for the period 1920 to
<br />1945, inclusive, Another study was made with t.he controls both at
<br />Otowi and at San 1\-1o.1'ciu1 In making these studies, full credit was
<br />taken for the effect on the flow of the stream by t.he operation of the
<br />reservoirs of the Sltn Luis Valley projcet for flood-control purposes,
<br />A detailed daily study was mltde from 1920 through 194 i, By cor-
<br />relation, the st.udies with the .control at Otowi were extended bfiCk to
<br />1890, There is att.nchcd hcreto It tltble whicb indiclttes for eltch of the
<br />years 1890 to 1947, inclusi\'e, the required storage capacity of t.he
<br />Chllmitn Heservoir and of n. reservoir Ileal' the Colol'ndo-Nc\V .l\Jexieo
<br />Stltte linc to control tll<' 1]0\1' of tile ri"cr at Ot,owi to 5,000 e, f. s, to
<br />7,500 c, f. s, and to 10,000 c, L s. to the extent that such rcservoir
<br />capacities could control the flow to those mtes of flow, Similar tables
<br />are attached whieh indictl,te the amount of storage citpncity required
<br />at the two locations for each Veal' from 1920 to 194i to control the
<br />flow at. San l\-1arcinJ to tile thre~e rates of fiow designat.ed above insofar
<br />as it would be possible to t:ont.rol the flow to those rates by reservoirs
<br />located at the two locations,
<br />The results of t,he study, toget.her wit.h t.he information,given in the
<br />reports of the agencies, indicate definitely that t.he construction
<br />of Chifto Reservoir to t.he capilCity propo::;cd is not economically
<br />fensihle. The. st.udies iJHlicnt,e tllso t.llllt. it, is prohnhle thnt, no f1ood-
<br />cont.l'ol capacity at or nefiT the Colorndo-New j\-Icxieo State line can
<br />be economically justifico.
<br />The annunl Lenrfit3 from sediment-tItian and flood control are'
<br />est.imated in the Corps of Engineers' report at $4,336,700, which
<br />include claimed bencf1t.s for the Bluewatcr-Toltec arca, The benefits
<br />clnilllcd for the pre\"C'.nt.ion of damage.s from inundation find scour
<br />between tbe Colol'ndo-Ncw l\!exico State Line and Elephant Butte
<br />I\escrvoil' U\'eJ'llgc $.384,560 pel' nnnuIII. The bendHs {'lnimed for
<br />t.he prevention of damogcs from st.renm-bcd aggradation, including
<br />the preyentioll of capitol losses thnt. would result from the rising
<br />water tnble due to st.ream-hed llggrtHlntion, average $:J,273,350 per
<br />annum. Some of t.he claimed benefit for the prevention of damng:cs
<br />from inundnt,ion and scour firc due to t.he ext.ension and improvement
<br />of the levee system, Se,'enteen percent, of t.he enpneity of the flood-
<br />cont.rol reservoirs is ullocated to sedimcntat.ion control, and the
<br />remnining 8;~ percent i~ allocated to thc:control of the fate of flood flows.
<br />Therefore, from 17 percent of the eapllcity of the proposed rcsC'l"\'oirs,
<br />there will be obt."ined at least 90 percent of the claimed flood-control
<br />benefits "ho\"O Elephant Butte Resen"oir,
<br />Only 1 percent of t.he sediment carried by the river is estimated by
<br />the Corps of Engineers to originate above the Chiflo Dam site, The
<br />sediment, passing out of Colorado results largely from scour of the
<br />river bed and bank cutting after the streams reach the Sun Luis
<br />Valley proper, 'Wit.h tbe flood control afforded by the San Luis Vnlley,
<br />project, the sediment passing the State line should be rednced so that
<br />t.here would be even less than 1 percent of the total sediment origi-
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