Tubewell Discharge Calculator (Trajectory Method)

Instructions

• Measure the inside diameter (D) of the pipe accurately, in cm
  
• Measure the distance (X) that the jet flow of water travels, in cm parallel to the top of the pipe (fig. 1)
  
• Measure vertical drop distance (Y) in cm
  
• Estimate tubewell discharge by substituting values in online tool

Advantages

• This method provides a simple, inexpensive, and practical means of estimating flow from horizontal and inclined pipes for field tests.
  
• No special training is needed to use this method.

Disadvantages

• This method provides only an approximate discharge from wells with horizontal or inclined pipes.
  
• Well flow should be constant. The top of the stream at the open end of the pipe should not vary appreciably.

Method Limitations

• Under ordinary field conditions, with reasonable care, measurements can be made in which the error seldom exceeds 10 percent.

• The most accurate estimated discharge will be obtained
  when the pipe is truly horizontal.
  
• The discharge pipe should be a straight length of standard pipe at least 5 feet long, so that the open end is at least this distance from the nearest elbow or bend in the pipe.
  
• If the discharge pipe slopes upward, the estimated discharge will be too high; if it slopes downward, the estimated discharge will be too low.
  
• The principal difficulty with using this method is in measuring the coordinates (X and Y) of the jet-flow stream accurately