315. The solution to Problem 35 indicates that the diversion of water from Mono Lake to Los
Angeles would cause the level of the lake to drop 19 meters.
A key parameter in this prediction is
the evaporation rate of 36 in/year, and the steadystate analysis gave no indication of the time
required for this reduction to occur.
In this problem you are asked to develop the unsteady
analysis of the Mono Lake water balance.
Use available experimental data to predict the
evaporation rate, and then use your solution and the new value of the evaporation rate to predict
the final values of the radius and the depth of the lake.
You are also asked to predict the number
of years required for the maximum depth of the lake to come within 10 cm of its final value.
The
following information is available:
Year
Surface Area
Maximum Depth
prior to 1941
56,000 acres
181.5 ft.
1970
45,700 acres
164.0 ft.
During these years between 1941 and 1970 the diversion of water from Mono Lake Basin was
56,000 acreft. per year and in 1970 this was increased to 110,000 acreft. per year.
The additional
water was obtained from wells in the Mono Lake Basin, and as an approximation you can assume
that this caused a decrease in
(see Figure 3.5b) by an amount equal to 54,000 acreft. per year.
Your analysis will lead to an implicit equation for
β
and a trial and error calculation is required.
4
m
±
315. Our objective in this problem is to develop an equation that can be used to predict
the depth of Mono Lake as a function of time.
This depth,
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 Winter '10
 B.G.Higgins
 Mass flow rate, Mono Lake

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