A detention pond needs to be designed with a total capacity of 30 ac-in. of storage. The inflow hydrograph for the pond is given in Figure P4-10. Assume that that pond is initially 50% full and outflow will cease when the pond is again 50% full. Graphically determine the peak outflow from the pond assuming a linear rise and fall in the outflow hydrograph. Draw the outflow hydrograph. At what time does outflow cease? In the following figure, the inflow hydrograph is completely accurate, but the outflow hydrograph is merely an approximation.

3 4 2 0 2 4 6 8 10 12 Time (hr)