220 VALUATION, DEPRECIATION AND THE RATE-BASE
Valuation of Reservoir Sites in Relation to Water-right
Value. — Passing now to the consideration of the value of reservoir
 sites it may be broadly stated that, in some measure, any
value thus or otherwise ascertained as appertaining to waterrights
 may serve as an aid in determining the value of watershed
 and reservoir lands or of other lands whose use is necessary
 to make the development of the water possible.
The value of such lands should not, however, be measured
by the necessity of the community which needs the water.
Their value is not what the community can afford to pay for
them; but they have at least the value which would be determined
 by the market for similar lands devoted to other uses.
They also have an additional value due to special adaptability
for use in developing a water supply.
It is owing to the desirability of bringing this excess value
of reservoir lands into some relation to the value of the water
whose development their ownership makes possible that it may
sometimes be found desirable to make the value of the waterright
 a measure of the excess of value (sometimes perhaps only
of the upper limit of the excess) of an assembled reservoir property
 over the value of the land for other purposes. While this
is not an established practice, it is one which appears to have
some merit. It is to be understood that the excess of the value
of reservoir lands over similar lands not available for reservoir
use as here considered is apart from and in addition to the value
of the water-right.
Where the water development requires only a few acres of
ground, as in the case of artesian supplies, particularly if the
land remains available for other uses, or when the topographic
situation is unusually favorable, a small fraction of the value
of the water-right might prove to be an adequate allowance for
special adaptability.
Value Multiple Applied to Reservoir Lands. — In such special
cases some use might be made of a value multiple such as has
become customary when rights of way are to be secured for
railroads and canals which are acquired usually at some increase