Flow Rate of Stream, Stream, Flowing Stream

Are you wondering how much water is available?  Here are some pointers to help you check and compute stream flow:

  1.  Select a straight run in the stream.
  2.  Make several measurements of the depth of the stream to get an average depth.
  3.  Measure the width of the stream.  If the width is not uniform for the run, take several readings to determine the average width.
  4.  Customary Example:  if your stream is 4′ wide and has an average depth of 6″ then (4 feet x 6 inches)/12 inches per foot = 2 square feet.
  5.  Determine the average speed of the stream flow
    1.  Mark and measure the length of the run to be checked.
    2.  Drop a float into the stream and record the time to travel 100 feet.
    3.  If the float takes 2.1 minutes to travel 100 feet, the surface of the stream is flowing at a rate of 100 feet per 2.1 minutes = 47.6 feet per  minute.
  6.  In summary, 2 square feet x 47.6 feet per minute = 95 cubic feet per minute (indicated flow).
  7.  A factor of .8 times the indicated speed of flow is used to get the average velocity.  This takes into consideration the water along the banks being slower thank in the center.
  8.  95 cubic feet per minute x .8 factor = 76 cubic feet per minute x 7.40 gallons per feet factor = 562 gallons per minute.
  9.  If it is evident there is not enough water to meet your needs, check other possible water sources.