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<br />124
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<br />CALIFORNIA FISH AND GAME
<br />
<br />FIG. 55. The mouth ot a small wash sho\ving destruction by flash floods, On the
<br />Colorado River about 35 miles above Blythe, May 1942,
<br />
<br />20,000 c.f,s,; the latter believed that the average annual spring-flood
<br />discharge might be of the order of 75,000 c.f.s, In Anon, (1941, p, 46)
<br />it is stated: "With the river regulated by Boulder Dam the steady flo\\"
<br />ranges from 12,000 to 20,000 cubic feet per second, The maximum flow
<br />to be expected is about 45,000 cubic feet per second, to control the usu~1
<br />seasonal floods. This may reach 75,000 cubic feet per second once ill
<br />about 100 years, " (It should be noted that, as far as practical, an even
<br />rate of flow is desirable for flood control, power production, and the
<br />diversion of water for irrigation and into the Colorado River Aqueduct,'
<br />.A. second control is possible at Parker Dam through the alternate
<br />impoundment and release of water. However, Lake Havasu's potential
<br />regulatory power is minimized bv the lO.foot limit to the variation i:J
<br />its water level already mentioned "as necessary for efficient pumping int,o
<br />the Aqueduct, The other dams below here can not be considered regn'
<br />latory as they do not enclose large storage reservoirs. ,
<br />While its flow has been stabilized to a great extent, the ColNado I~
<br />still not tamed, and plans exist for further regulation. The projecteu
<br />Davis Dam at Bullshead about 67 miles below Boulder, which would
<br />back the water up close to the foot of the latter dam, is desii!'l1ed tc.
<br />minimize the effects of large releases from Lake Mead for power 1'1
<br />excess of irrigation requirements. Flood control dams are contemplati"J
<br />for the Williams River, at the Alamo site, and at the Sentinel site on
<br />the Gila, which already has some flood protection.
<br />Regulation of its flow can mean that there will no longer be tb~
<br />alternate periods of flood and dessication which are so harmful to aquat:r
<br />life. And, provided that the rise and fall of the river is gradual., a
<br />certain amount of continued fluctuation should actually be bendiclal
<br />through the accompu.nying fertilization from the land.
<br />
<br />~ - ---- --- - -~-.:.-= '-._-':""';:':":~-.; ~ ~~:-:.:~,>:';')
<br />THE FISHERY OF THE LOVlER COLORADO 'RIVER --- - -1~1i -~ . ~
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<br />Silt
<br />
<br />.Woothick to drink; too thin to plow" is the old !>awwhidLo~e, ' ' ,.
<br />~d the Colorado. It still does describe it above Lake Mead where --'---:c-:,....-
<br />.tJoad continnes undiminished and where it is a source of wonder',~c
<br />"yfish could endure snch heavily charged water. The aridity .", .-- .-,,",
<br />'limate, soft deposits, lack of vegetation, and violent floods are-
<br />the reasons for the great erosive action which has made the
<br />..0 the greatest silt-carrying stream in the world.s
<br />
<br />'':t'he heavy silt load of the Color~do River above Lake Mead, Grand Canyon.
<br />J~iC-. AprIl 1942,
<br />
<br />vt~.ough some of the first products of erosion may be large in size,
<br />tiine the load has reached the lower river its fragments have been
<br />verized that they approach the fineness of Portland cement.
<br />as of samples of silt have been taken from the lower river and
<br />, e, of this could be classified as coarse sand. In typieal analyses,
<br />"~! cent has passed a standard sieve of 200 meshes to the inch.
<br />..~~d Blaney, 1928, p. 3.)
<br />:silt has been classified into two major types: the fine suspended
<br />""",~e_heavier bed silt "hich is carried along near the bottom of
<br />cC"~',' " These types are interchangeable to some extent nnder
<br />~h!dra~c conditions. Even at quite low velocities, (any
<br />!wo-thirds of a foot per second) the finer silt continues in
<br />pn; 'Hence even l~w-g.rade irrigation canals have been extremely
<br />ythere the veloclty IS retarded the bed silt is deposited tem-
<br />;Ol:llY to be picked up again during floods and so move pro-
<br />:;;~~<!:wnstream. .
<br />
<br />is Its only strong competitor tor this title. (Senate Hearings betore
<br />'on IrrIgation and Reclamation, 69th Congress 1st Session Colorado
<br />,Part 1, 1925, p. 27.) "
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