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<br />To: The Secretary of the A~
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<br />cocposed of a representative of onch of the trIee states and of the United
<br />States. Future developoent in the basin must coepl:' tTith the effective
<br />te~s of the Coopact.
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<br />4. Serious floods in the Rio Grande basin are caused b~ sno~-~elt
<br />runoff froe the ~ountains so~eti~es augnented Q)P rainfall, or 1r; heaV)' rain-
<br />fall alone either fro:::l general otorr.a or local cloudb.1rsts. Floods of the
<br />first type occur in the period, April through June, and are of large volur..e
<br />and long duration. Floods of the second type occur fro!:l April tl:rough
<br />October, are of s~ort duration, and ore of relatively largo or soall volume
<br />dcpendin& C~ the character of the store, ':1~ether cer.eral or a local cloud-
<br />~~st. 0: the 16 ~ajcr floods durir.g the period 1874 through 1943, 9 re-
<br />sulted froc sr.ow ~elt auccented by rainfall, 2 froc snow ~elt 31one, 4 from
<br />general r~ecipltation, and 1 fro~ a local tr.understorm of l~r:e nagnitude.
<br />T!1.e largest flood of rece!'.t record occurred durinc I:o.:r., June, Ilnd July 1941,
<br />and caused dllrBges a[~regatine over 32,000,000 in t~roe localities alone.
<br />These locc11ties rriti: estinated da::n.:es are: E~:,~nolo. Vo.lle:", $203,:00;
<br />!:iddle Valley, $1,694,800; and ::J.ue,::ater 7alle:r, :167,800. Do..":'.ages fror.:
<br />the 1941 flood in ot~er s~Aller localities ~ere not evaltmted. AveraGe
<br />aP~~ flood d~~aEes caused cy inundation and scour are estinated at
<br />$l..U,)OO in the Espanola, :'iddle, and Lower Valleys, end S29,lOO in the
<br />21uer.ater Valley. In addition to direct darnaee due to inundation and
<br />~cour, floods carry enorr.ous quantities of sediment into the lo~er reaches
<br />of trjbutaries and into the ~ain stre~ channel, chokinr and .reducing their
<br />c8Facities and 8.grreding tr.e river bed. River bed ageradation reduces ef-
<br />fective levee he~bhts and also causes a rising ~ter table that waterlogs
<br />adjacent 8bTicultural land. Past darages fror.: this source have not been
<br />nonetari1y evalU3ted but it is noted that they have accur.ulated to the ex-
<br />tent that the econo'"'J of large areas is seriously affected and unless cor-
<br />rective ~eas.~cs are uu:en soon, they will continue to a point where ~ost
<br />of the riddle Valley is rendered coor:ercially tL~productivc.
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<br />5. ::umerous icprover:lents fer the alleviation of flood d.a.r\ages in the
<br />Rio Grande basin have been provided bo; Federal and local ar.encies. A proj-
<br />ect for e~ercency repairs tc the Ciddle Rio Grande Conservancy District
<br />levees in the i.:iddle Valley na.s completed by the Corps of Engineers in co-
<br />operaticn with local interests in advance of the spring runoff in 1944.
<br />The total estinated cost of this project was $645,750, of ~hich the Federal
<br />cost to June )0, 1946, was $4l0,652. There is no existing project for flood
<br />control under the jurisdiction of the Corps of Engineers within the I~w
<br />~exico portion of the Rio Grande basin. A project for local flood protec-
<br />tion at Creede, Colorado, was authorized by the Flood Control Act approved
<br />Deceriber 22, 1944. Proposed irrigation reservoirs in the San Luis Valley
<br />Project, Colorado, authorized for construction qy the Bureau of Reclama-
<br />tion, include provisions for regulation of floods and reduction of flood
<br />darages wi thin San Luis Valley. The Cal:al.lo Dam and Reservoir constructed
<br />lTJ the ?ureau of Reclar.ation as a part of the Rio GranCo Project develop-
<br />oent has 100,000 acre-feet of flood control storage capacity provided at an
<br />allocated cost of ~1,5OO,OOO, which was borne b)r the International Boundary
<br />Comcdssion. The Co~ssion also has canalized the RiO Grande channel
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