7625

• UCREFRP Catalog Number: 7625
• Author: Stone, R. C., L. Fields and K. Miller.
• Title: Lake Powell Post Impoundment Investigations.
• USFW Year: 1964.
• USFW - Doc Type: Progress Report No. 2,
• Copyright Material: NO

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run al~ost vertically (from surface to bottom) r~ther tha~ horizontally

(from one end of the l2.ke to the otl-;'2:") as might be expected. U::doubt.ed':"y

'this is a function of the colder ',.,rater cOLtributed by the Colorado and the

colder climate at the northern end of the reservoir.

Lake Powell begins warming in ~ate ~~ch or early April. U:1stable

therr.1oclines may develop until July when a permanent stratification is

formed. Maximum temperatures occur. about August} w'he:1 the surface is 800

to 820 F.} a:1d the thermocline betwee:1 730 and 680 F. Water in the hoso-

thermic region below the thermocline is about 650 F. A COOli:-lg trend a:1d

thermocline breakdown is evident in October. Glini:num surface tempcratercs

of about 500 F., lower reservoir, and 400 F., upper reservoir, are reac~led

in March. The great majority of the lake has been near 490 F. at this tiGe}

however.

The one station (Ch3. Ca:lyon) situated in the San Juan ar:7l sho...:s a

temperature pattern and chemical readings very much like the t",ain-stem

(Figure 5 ) . Dissolved oxygen values} while not differing greatly at -;;he

surface, did show a serious sag to values of 3.0 ppm a:1d less in and below

the ther::Jocline.

Secchi Disk readings (Table 3) show high visibility in ~;'O late fall

and winter after all effects of the runoff have subsided. T:le readinGS S:iO',,.

a clear, faintly colored water. Runoff from the Colorado and San Juan

Rivers begins in late Hay and continues well into July. In June of 7,his ye~'.r

the effects of runoff on visibility continued '..Jell down reservoir, diminisl1-

ing rapidly betw'een Rock Creek and. L:lst Ci1:l:1CC. By J:J.te July ~l ~~icnll'ica!lt

decrease in turbidity had progressed up reservoir to about the cO:lfluc'lce

of the San Juan. During the entire year, the region Hithin several ~,lile:3

of the Colorado remained completely affected by its inflow'.