Measuring Head

You will need to measure the vertical drop in feet or meters (referred to as head or fall). 

Builder’s optical level - measure the fall of the river as you progress along its length. This is good for lower falls and it is very accurate.

Low cost laser level - at dusk or in low light conditions project a horizontal beam and using a long staff measure the vertical drop. You may have to repeat this at a few locations.

Measuring Flow

IMPORTANT: "Gallons," "gals," and "gpm" refer to the US Imperial Gallon , as opposed to the UK Imperial Gallon.

To measure flows in the 20-60 l/s you should use a weir. Measure flows in both the wet and dry season at least 1 week after rain. There are plenty of resources on the internet to assist you. Search for "V notch weir" or "Rectangular weir". Locate a weir size that will fit into the space you have available for measuring the flow, you may need to sand bank the river as per the picture below.

Cable Distance

Measure the cable distance accurately with a tape measure.

The shorter you can keep the cable distance the better, but sites up to 1,000 m away are often economically viable using 2-core aluminium cable. Long run cable costs can kill the economics of micro hydro unless you have a very good site and an economic need, for example displacing high cost fuel generation.

Preferred Voltage

New clients should use 48-volt systems. This ensures cable/regulator and inverter costs are lower and that the systems efficiency is higher. For smaller systems, 24 or even 12 volt might be appropriate.