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<br />fi. Table 1, presented through tbe courtesy of Mr. L. V. Wilcox, shows
<br />tf analyses of river water near Yuma before and after control of the river
<br />l! by Boulder Dam. Altbougb th' samples """ ,0Uerted over limit,d
<br />. periods, thev at least offer an indication of the changes in chemical con-
<br />~ ditions wro~ght by impoundment in Lake Mead and the fairly regular
<br />f1: release of water into the lower stream, In commenting upon these
<br />1~ analyses, M.r. Wilcox (letter of March 10, 1944) says: (in Table L\.]
<br />~;\ "you will note the wide variation in total solids and in several of the
<br />i~ constituents . · .. This was characteristic of the river prior to the
<br />i4:"'~~:,',..,-::~:----:-___timejt~~s_~~ntr.Olled' , The flood water of May, an",d" ,J,un, e w,as,of r, elati\'ely
<br />i low sal~mty, ~'li.ilethe low flowst ot~er, seasons of ih_e_2'ear :!a~ often of
<br />~ very hIgh salimty . · · . The sigmficant feature of .... · (the,
<br />~ analyses in Table 1-B made after control by Boulder] · · · is the
<br />. remarkable uniformity, as to total salinity and composition."
<br />li In g,n"al, it ",,,ns that th, dlert of th, dam has been ben,";,ial to
<br />I &h lif" ""PeriaUy in stabiliring th' ,ompo.ntion, ,edncing alkalinity,
<br />il and ,educing total d_lved solids. Th, high concent..tion of total di,
<br />it, ", . S<?lved solids remains none~heless one of the outsta.nding features ,of this
<br />\l' nver, as of most streams m the southwestern Umted States, whlCh are
<br />. , characteristically higher in this respect than in any other part of the
<br />, country. While the concentration here of around 700 is evidently U0t
<br />,. , too high for the fishes now present, it shou}.d be noted that concentrations
<br />'" of around 1,000 at the State trout hatchery at Fillmore, California, are
<br />D1 suspected as the reason for the inability to keep trout eggs alive then'
<br />.1% ii through the eaTly stages.
<br />:~ i~ A considerable amount of the available fishing water close to centers
<br />.i I'. of population is represented by the drain ditches (channels carrying sub-
<br />'~ t surfac" inigation wast,water, and ,pill.",~t,d~om canals). Thech'''''
<br />'.~ ' ter of dramage water, as compared WIth mcommg canal or nver water.
<br />~ " is d'p,ndent upon a number of fad"" sueh as th, ch,mical..mpc<itiOO
<br />:" .' and pem"ability of th, soU, amount of inigation wat" applied, ,k It
<br />~ If may vary considerably in different localities and at different seasons,
<br />, ,.~ t't The examination of sewral analyses secured from the Palo Verde Irriga.
<br />i II tion Dishid show,d th, eoncent,ation of di"olved soli,h to b, mu.k,dl,
<br />;! I' bigher in th' duinag' wate< tban in the rive' wate< at th' intake. ''"
<br />;~ ~)!ay 31, 1940, fo, ""mpl', the total di"olved solids at th,. intak'. wee"
<br />~.~ ,. ~6U p,p.m., and 1,5/3 p,p,m, at the Outfall Dram. Some dramage dit<:ht."S
<br />i pro~d' ",ry good fishing; othm ,eem to b, d,fici~nt in ,uppot.ti:"
<br />f,;\' desirable game fishes. Only careful study can determme the reasons tor
<br />~ ,uch diff,,""'" Th", is at least a po"ibility that diffmnces in ,hemi.
<br />ii. cal composition may be of importance in determining whether or !lot Ii
<br />~ ",tain ditch w;U p,oduce an abundant crop of gam' fi,h 0' on' in whi,b
<br />ll!1 coarse species predominate,
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<br />CALIFORNlA FISH .!.1'<" GAME
<br />
<br />BIOLOGICAL FACTORS
<br />
<br />Vegetation
<br />
<br />In the arid land through which the Colorado flows the vegetatIon i~
<br />relativeh'- sparse except near the riyer. \\onere the stream is bord~r~
<br />by rocky ,cliffs or by bench lands there are but few plants which Jl)lgu:
<br />be expected to haye an influence on aquatic life. Cacti, creosotebu..--.L
<br />
<br />La;;d Plants
<br />
<br />
<br />THE FISHElty OF ~E LOWER COLORA~L
<br />uv tU v tAt ._,
<br />
<br />.----__...u....t_
<br />
<br />:~'t, 0 ~
<br />
<br />/.pesert vegetation and the willow-cottonwood assC'Ciati
<br />:' between Blythe and Parker, Feb, 1942, on, Colorado River
<br />
<br />
<br />~,bur-sage (Franseria)-the list is 10nO'-may be common, B t
<br />:re u~land plants. Nor a~e the plants of the washes such ~ ca~-
<br />(Acacuz), or ~f t~e mesq Ul te (Prosopis) and saltbush (Atri lex)
<br />.. ab~ve tb, npanan ""n, usually of importance to th, rive,. P
<br />~erem"e, fowever, severa~ plants "hich through their proximity to
<br />ver are. 0 much greater Importance. Foremost amonO' these are'
<br />.(Sal.~), co~tonwood (Populus fremontii), seepwillow'" (Bacckar~
<br />,"~sa), T.arnanx (often caUed salt-cedar, 10caUv) and arrowweed
<br />a seru:e~). These plants, in various combii'1ations often form.
<br />stands or Jungles along the area..<; inundated by hi!!h ~ater Th
<br />l'.,,^,m~ .."",d. ,wn in part, off" ,h,lt" for fuh", Tb,; 'o~
<br />, ~d directly as Hl the form of seeds and lea yes , other f~o~ '. .
<br />!,.!,.",:.e",lther through fertilization of the "ateI' or as 'a sou f'. mdl-
<br />."'" , ree 0 msect
<br />
<br />;~~capriciousness of the Colorado has and still doe- ca 't t
<br />'p....ms' f"qu~ntIy. Wh,n tbis o"u" tb,,, plants;:", d~:~'~ .d
<br />..mbsequent enrIchment of the water. It is true that thO ! h
<br />.. ~ .b, a v",>, t,mpo,",y on' in tb, main chann,l H: '~c .;
<br />;9f considerable value in the quieter water whe're su~e~~~r~
<br />.' eJong enough to decay, '\\nere the water level has been raised
<br />,-.-:aone ~ds.large areas wh~re not only the plants of the willow-
<br />~Winasso<!1atl~n ha,:e b~en mu~dated, but where the water has
<br />~I,any les~ strIctly rIpal'lan speCles, )fesquite and saltbushes
<br />.}~!:some tIme as submerged zones of shelter may
<br />"=11--<.1914) has devoted a study to the pl~nt assoeiations on the
<br />;~,,!ith reference to their influence on birds and m Is
<br />t~eIT effect on aquatic animals is far less, it must rece~~~n:
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