The rapid broadening of the Taylorsville basin surface causes its storage volume to increase at a high rate after spillway level is passed. The Huffman storage also increases rapidly, while the lowest rate of increase is at Germantown. The capacity-depth curves of figure 38 do not show the minor depressions which appear in the corresponding area-depth curves. Without exception they are remarkably smooth and regular. EXPONENTIAL CURVES FOR AREA AND CAPACITY Inspection of the area and capacity curves for the different basins, figures 37 and 38, suggests the possibility of approximating these curves by lines having definite mathematical equations of the exponential type. This operation permits calculus methods to be used in solving problems regarding inflow and outflow relations for the basins, and makes possible a great saving of time and labor in certain kinds of computations concerning retarding basin action. For any depth of water in a retarding basin, let A area of water surface, in acres, = storage volume of retarding basin at same depth, in acre feet, H=corresponding depth of water in basin at dam, in feet, 0 corresponding outflow rate, in acre feet per hour, C=constant, depending on form and dimensions of retarding basin, B= constant, depending on size and construction of outlet tunnel. В In the basins of the Miami Conservancy District, it was found practicable to approximate the area curves by semi-cubic parabolas having the type equation: When the approximate area curves are established by this formula, the corresponding storage curves are automatically fixed as five-halves power parabolas, since dS=AdH, giving In order to have these equations available for use on any retarding basin it is necessary to determine two quantities; first the constant C, which will be different for each basin; and second, the elevation which will be considered as the zero depth in the basin. In fixing these quantities there are two conflicting sets of considerations which must be kept in mind, each being applicable to its own class of problems. These may be classified under: Case 1, where the zero depth may be |