Basic Hydro Power - Part 3

Suddenly you have to measure the head of a water stream. What kind of method would you use? Before answering such question, let's go back a little bit and review the map. With a quite detailed map someone can determine which position is best for the intake and power house and other components of the plant The planner has to draw a sketch and put the rough layout of the power plant on the map. The map should be quite detail (1:25000 scale might do). From the map, one can make an approximation of the head. Measuring in the field will verify the approximation.

There are some methods to measure head. Simple one is using barometer. two different level of soil will have different level or air pressure. Barometer can do quite good job if the head difference is significantly high. A 20 meters head, you will not use barometer. A transparent hose pipe with water pressure gauge will also do the job. As long as there is no bubble in the pipe, this method will do quite good. The limitation is the pressure gauge. Usually 1 atmospheric pressure (ATM) corresponds to roughly 10 meters of height difference. This method will do good if there is no extreme terrain (e.g. almost vertical cliff).

There are other methods for example the clinometer method. This needs small trigonometric calculation to find the head difference. There is also theodolite method which also needs calculation. GPS method that gives you rough estimation of the head. There are many  gadgets that makes people easier to work. There is a new tool from Nikon that can calculate the head difference for you. Head measurement can be done from a distance.

Both head and flow are two most important thing to measure in sizing a hydro power plant. Measuring head is much less troublesome than measuring the flow, however wrong measurement will create design mistakes. Be sure that you measure the head carefully and according to the plan.