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Ditches in California.—In
the mining districts of California ditches are constructed boldly, with
steep grades and on irregular lines with numerous sharp curves. The
cross sections, originally uniform, become more or less varied.
Absorption, percolation, evaporation, and leakage reduce the flow. A
distinct, reliable factor for each of these sources of loss cannot well
be incorporated in the coefficient of discharge. If, then, it is
intended to cover all of these common sources of loss by such a
coefficient, its value must be a material modification of values
commonly given in the text books. It would be certainly an affectation
of accuracy to apply so complicated a formula as that of Kutter in such
a case, since the modifying conditions, which can be estimated but
roughly, call for a large reduction of the calculated result. This will
be apparent from the measurements of discharge given further on. The
simple formula,
Q is the quantity of water which the ditch is capable of carrying in cubic feet per second.
a the effective area of cross section of ditch, as originally constructed, in square feet.
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