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<br />from Li'ls VeRas and cl;uk County Scv.'\ge Trp<ltmellt Pl<lnts rail he pzpecled to <br />t-4 decl'ea,:.;e PIOdUClivity in Lah' Mohavp. ,111d pnssillly Lake llavdsu. The slight <br />L'"" decrease that OCCUf"IPU in chlorophyll a (,'O!lrenfri1l ions in Llke Hohol\'e dlll ing <br />C; 1982 pl'ohallly reflel:ts the redll<.'lioll in phosphollls loading. Productivity in <br />(.v the Boulder Basin are<l of Lake Meild has llndel-gone it steady rJecline since the <br />late lQ]O's \Jhen phosphorus loading flam Las Veg<ls Vash began to decreRse. <br />This appealS to he il major filet!)! reslJonsible for the declille of the fisheries <br />recently experienced in the reservoir. Similar redllctions ill the productivity <br />of LaYe Mohave \Jill probably also result in a decline in fisb production. <br />This problem should be calefully evalUilted in ongoing rcvievs of ('un-ellr <br />vRsteIJater rreatment practices at the city of Las Vegas and CIClrk County <br />Sevage Treatment Plilnts. A relaxation of the phosphorus standards at Las <br />Vegas Bay during the t.linter and it tightenillf, of the sLwdanh:, as pt-oposerl hy <br />Nevada, !/lay be t.lan-anted consirleling the hw ploductivity ill the river system <br />and the damage occuning to the belleficial uses in Las Vegas Bay. <br /> <br />Lover Color,ldo River Bilsin Reservoir Monitoring rl'oerilm _ The LO\Jer <br />Colorado Region of tile Bureau of Reclamation (Reclamation) funded a 2-year <br />monitoring PI.ograll1 on Lilkes Mp"d, Mohave. altd H;'tv<lsll. Tilt> program \Jas <br />implemenred in Decembe,- 1985 and ('ompleted in Nnvemb!'r 1987. The major <br />portioll of the study IJ<lS ('onrlucted unde, contract by the F.:nvilonmental <br />Research Centf>r, Univetsity of Nevada, Las Vegas. Data ""ele collectPd on a <br />monrhly basis at 13 stations on Lake Mead. j stations on J.:lke Hohave, and 3 <br />stations 011 Lake Havasu (2 of those IJere qual-telly). Vilter column profile <br />measurements at each si te included pll, .....'rel tempel"rlt\1re, dissolverJ oxygen, <br />and electrical conductivity. Spcc-hi depths and limnophotometer meaSlll'ements <br />vere mRde. Vater samples ....el.e taken flom various depths to be analyzed for <br />nlltl"ients. zooplankton. chlorophyll. and for their major ions. Cunent <br />veloci ty measurements vele also milde. <br /> <br />A summal.y of the <br />lhe Environment;-tl Sciences <br />Deliver Office. <br /> <br />Re:::ef vf'li I' <br />Sect iOll, <br /> <br />Moni toring rro~r<lm ....i 11 he conducted by <br />Resf.'al(;h Laboratol.Y S(:fvices Division. <br /> <br />Redilmalion has been ....orking: \Jith the Natinnal Park S!::rvin:', Arizona <br />Gi'lme <lnd Fish Depanmellt, alltl Nevanii Deop,utmellt of Vildlife in the <br />investigation of '.lhilt appeill"S to be a decline in the bla<:k bass tishelY of <br />Lakes Meild and Hohav€'. As palt of this investigation. a second portion of <br />the contract evaluated the poteutial for successfully stimulating algal grolJth <br />on a large scale in Lake He.ld using .utificial fE'ltiliz.1tion. <br /> <br />The principill goals of the prpfpniliz<'ltion stllrly IJe]'e to rlptermille <br />the mnst sui table types of fel t i 1 izer for lal-gp-sc<'lle addi t ion:; to Lake Mead, <br />to evaluate methods of fertilizer app1iciltiollS. alld to mal-:e lccommendRtiollS <br />regarding the frequency of fr-rtilizer <'lddi t ion!>. <br /> <br />LallOratory and cove experiment<=: indicated Ih;!t liquid ammonium <br />polypho~phate (I(l~3~~O) and eithel- liquid ammonium nitL.te (20-0~()) or <br />granular ammonium nitrate (Jl.-O_(1) IJele the most .';t1itable fol' nutrient <br />enhancempnr. Dispersal from sln;.:ly moving hoat.'; appeared to be the most <br />cost-effective method of llniformly applyillg fertilizet. River illjection of <br />fertilizel' vas examined anti determin['danon-:iable methorl of improving lake <br />fertility because of inflo... densities and lake sttatific,.tioll. <br /> <br />II T 5 <br /> <br />". <br />