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<br />Method A.--The tons per acre-foot values were obtained from the composite
<br />analyses that were avai lilble for each streilrn stat ion to the 1969 wilter year.
<br />After 1969, cornpositing of dilily silrnples was discontinued. Three composite
<br />samples were usually prepared each month by mixing together equal volumes of
<br />daily sarnples collected from the 1st to the 10th, from the 11th to the 20th,
<br />and during the remainder of the rnonth. Silmples were sometimes composited for
<br />shorter periods on the busis of specific conductance of the daily samples. A
<br />dischilrge-weighted ilveruge anulysis for the yeor is computed from the compos-
<br />ite surnple analyses and approxirnates the composition of al i of the water that
<br />passed the station during the year. The annual dischilr.ge-weighted concentra-
<br />tion, in tons per ac,-e-foot, is multipl ied by the acre-feet of flow for the
<br />year to give the salt load, in tons, that passed that site during the year.
<br />
<br />Method B.--The dilily dissolved solids are multiplied by the daily flows,
<br />in cubic feet per second, and the necessary conversion factor, 0.0027, to give
<br />the daily load, in tons. The daily tons are totaled to give the annual load,
<br />in tons. To obtain the annual dissolved~sol ids concentration, in tons per
<br />acre-foot, the annual tons are divided by the annual flow, in acre-feet.
<br />
<br />Method C.--This method uses the daily discharge and the two regression
<br />equations: (I) Dischilrge versus specific conductance, and (2) specific con-
<br />ductance versus dissolved sol ids, to compute the annual concentration of dis-
<br />solved sol ids in sUeilmflovJ passing the stiltion and the annual load, in tons.
<br />
<br />MeUlOds D and E,--These methods compute the annuill concentration of the
<br />Colorado River above the Dolores River by subtracting the annual load, in
<br />tons, of the Dolores River neilr Cisco from the annual load, in tons, of the
<br />Colorildo River near Cisco and dividing this load by the annual flow, in acre-
<br />feet, of the Colorado River near Cisco minus the annual flow of the Dolores
<br />River near Cisco. This value is then appl ied to the flow of the Colorado
<br />River at the State 1 ine. Method D uses the loads for the Dolores and Colorado
<br />Rivers computed from daily specific-conductance records at the specified sites
<br />as in method B, and method E uses the loads for the Dolores and Colorado
<br />Rivers computed from dai iy disch~rge records at the specified sites as in
<br />method C.
<br />
<br />The annual tons per acre-foot values for each station for 1952-74 are
<br />given in tilble 4. The annual s<llt load, in tons, for the several stations are
<br />given in table 5. The salt loads shocln for different methods of computation
<br />are in re"sonable ag,'cernent at each site. Better than 50 percent of the time
<br />the loads are within 10 percent of each other, and about 95 percent of the
<br />time they arc within 20 percent.
<br />
<br />The salt-load increase frolll the G,-and Valley area computed at 09163530
<br />Colorado River below Colorado-Utah State 1 ine station and at 09180500 Colo-
<br />rado Rive,- near Cisco, Utah, station is given in table 6. The load at sites
<br />09095500 Colorado River near Cameo, Colo., 09105000 Plateau Creek near
<br />Cameo, Colo., and 09152500 Gunnison River near Grand Junction, Colo., arc
<br />subtrClct:ed from the load at site 09163530 to give the salt-load increase at
<br />the StCltc 1 inc. The loaels at sites 09095500, 09105000, 09152500, and 09180000
<br />
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