|
<br />I,~.:r ::;, ~ t1- -- -----"12-6---.---- CALIFORNIA FISH AND GAME
<br />
<br />11:-"- ," .-;i '1' rted allows one to present some startling
<br />~ ~ '/:.: ~ ,- T~e quan~ity of 51 t transpo f the new dams it was estimated .by
<br />~J< ',:}- ;":' t statistICS. PrIor to th(1~2e:)Ct~~~ ~e total silt load at Yuma (exclusIve
<br />,t., .. g t Fortier and Blaney' -feet 'annuallv. About 80 per cent
<br />i~ iij ,... :: :?: =:;:;nd~n;il~~82~ge:~:~~~e~:~tdep1l:~lSo~~o;;,~ ':~~~;
<br />
<br />~~ .~.~.. · to cover about 215 square ?II ;0 each day weighed almost half a
<br />~;~i~i:,~; '.,~ ; suspended silt alone passIng uma
<br />
<br />;pq'v '~ a~: million tons. 'ways in which this silt may have 1"'1'11
<br />3,n:i;;t ~: There are sever,al differ;nt .1) The bed silt is moved along 1l1t'
<br />\~~n ,',' ~ . deleterious to aql;latlc organlsnlS'r in waves or steps like sand dune~,
<br />G],~;- bottom ~ a roll~g mov~ment 0 result of sudden displacements of
<br />;,;to" ,It. _ .___ -The-."boils".seen In the rlv~r are the-h '-'d- - -'" Would qUiCKlY smother
<br />,-h . - - The progressIOn of suc unes bl' h d
<br />('t;'1. such masses,. . h had had a chance to become esta 1.S e, .
<br />· ~:~ any ~ood orgamsJ?8 1~~~c f ther showed that for every foo.t of ns~ m
<br />Studies at Yuma In .ur t f approximately 2} feet m the nver '
<br />the river ~ere was a sco(fmg ou19~1 p. 273.) Since the stream has
<br />bed. (Calif. Colo. R. . omm., of ' reat proportions, it is clear that
<br />been subject to many .r~es, some tt~m The character of the bottom
<br />there ?as. b~en no stabIlIty ofb:eli~le ch~nce for the fi:m e81:ablishment
<br />depoSIts m Itself ~as offer~ f ds (2) The comparatively mert d1Pffi.
<br />of organisms servmg !,-S fi.s .00 . it does from areas where there is but
<br />ical character of the SIlt, co~ as wth of or anisms. The major
<br />little soil, has no~ be~n ~on&UClVe ~;~~ ~~llingwood~ 1892; Moffett, 1!)~3;
<br />constituent of this silt lS S ca. 3 Li ht is essential for the prOd~C~l?n
<br />Fortier and Bl~ey, 1928f) J l th; microscopic ones form the lllltlal
<br />of green ~qua~lc plan~S? wIt ~as been impossible for light to penetrate
<br />link in a rIver s food c(4a)mThe mechanical effect of silt on fish, other
<br />the turbid waters.
<br />
<br />
<br />
<br />':">~>:'-;""'~'~'o:::~ ".;
<br />-' '. ~,,;, ;,..,".~~
<br />~"organism8 and' their eggs has not been stUdied in this river, but '~---.:::;'~;~:;f~~
<br />'have been somewhat delE!terio:w;.w (5)',Finally, ~ven if ,therehaa~-:':-.c;2~tt~;_,_ -
<br />'large number of game 'fishes present, it is well knoWIi that-cori:"--<;'d;;Cc
<br />. ,muddy water does not promote good fishing. , ,,:.:;,,*
<br />'on1yway in which'silt might seem to have been useful to the '," ':::,,':'::~;.
<br /><"'_Was in lessening their. vulnerability to predators. GrinneU--~'~~:-X~:_
<br />.s~~;:117) remarked, ". · .' the opacity of the moving water _w,
<br />"~ain stream is so complete as effectually to prevent fishing here
<br />'ivOI-oUS birds in the usual manner."
<br />3mould be mentioned that, ., Although it requires very little
<br />^~tO transport the silts of the Colorado the material in suspension
<br />settlesrapid!y when_.the_.water ,.is ,brought...to.rest ._.:~!.
<br />dOubtedly- greatly influenced' by' the chemiCal composItIon of
<br />which produces flocculation." (Fortier and Blaney, 1928,
<br />,also Breazeale, 1926.). Despite the turbidity-of the main
<br />. ere have always existed lateral-channels, depression.'i; over-
<br />and small bays where the silt had a chance to settle out.
<br />y the bulk of the fish populationS were found here before
<br />ere built." The introduced game fishes were not abundant
<br />'daccording to the best report the native fauna was rather,
<br />'(1937) has attributed the limited fish fauna of parts of
<br />'n.e and Missouri to muddy water. "..c--
<br />been estimated that Boulder Dam would hold back 137,O()()"
<br />',.silt annually from the lower river. Since its erection and'
<br />'other dams below it, there has been a material dimini~hment
<br />"c'" 'all of the lower river. In 1940, the annual silt content at
<br />'only 2,071 acre-feet according to U. S. B. R. Yuma Project
<br />',of the silt is removed at Boulder, and for about 25 miles
<br />'~ter is unclouded._ The lower por1ion of Lake Havasu is clear,
<br />erlor'some distaricebelow Parker Dam has been :heed of silt.'
<br />the silt load has decreased tremendously; it should be noted
<br />'. not hope for the immediate creation of the ,. silvery Colo-
<br /><ng. ' The clear water which issues from Boulder soon becomes
<br />. 'as the stream meanders and cuts across alluvial flats. The
<br />of Davis Dam would extend the section of clear water further
<br />'m, out silting in Lake Havasu and aggradation in the Needles
<br />Wages cutting unless the stream should become entrenched. In
<br />riof the river it is even to be expected that the water will become
<br />. "than it is now. At present much of the load picked up below
<br />J,;{:)aJl!is being deposited in the extensive silting basin behind
<br />"1Jam.10 But as this basin fills (and it is filling rapidly) the
<br />, t~ again move downstream. .At that time it is planned to
<br />.-,'.~ater entering the All-American Canal, and this silt will be
<br />,utinto the river below the dam. Even with a good control of
<br />~a:~Bill Williams, there is no insurapce against cloudbursts and
<br />. 'ent products of erosion which can be washed into the river.
<br />silt content has been and will be so lowered that conditions
<br />suitable for fish throughout most of the river.
<br />
<br />
<br />~#;~------ ----=:-::_--..:-~.--:---' - - '~
<br />>~"" THE FISHERY OF THE LOWER COLORADO RIVER
<br />
<br />127
<br />
<br />,~
<br />~""'ft'
<br />
<br />FIG, 57, Upper end or Lake Havasu,
<br />
<br />oj 40l
<br />Silt deposition and erosion, F~\", " 0'
<br />
<br />~r~.IB a flood on the Bill Williams, the discharge from Parker Is cloudy.
<br />
<br />drilnage area above this dam is about 187,000 square miles, or this
<br />",on trois about 167,000 and Parker about 10,000 square mlles.
<br />
<br />--.-...,-,.-, ,.
<br />. - ~- ;'-;. ':<_':.::::;:.:'
<br />
<br />.-J,);:
<br />
<br />1
<br />
<br />tI
<br />!
<br />i i
<br />I I
<br />l- f
<br />-If, ~ 'I
<br />j
<br />. ',' ~i
<br />[=i
<br />t=-t
<br />
|