Sample Calculations
In the present example (hourly time step), the flows are summed and then multiplied by 3600 seconds to determine the volume of runoff in cubic feet. If desired, this value may then be converted to acre-feet by dividing by 43,560 square feet per acre.
The depth of direct runoff in feet is found by dividing the total volume of excess precipitation (now in acre-feet) by the watershed area (450 mi2 converted to 288,000 acres).
In this example, the volume of excess precipitation or direct runoff for storm #1 was determined to be 39,692 acre-feet.
The depth of direct runoff is found to be 0.1378 feet after dividing by the watershed area of 288,000 acres.
Finally, the depth of direct runoff in inches is 0.1378 x 12 = 1.65 inches.