Estimating WaterHead and WaterFlow of Micro Hydro Power Station/Plant

A full feasibility study will needed to generate accurate waterhead and water flow rates, but it can be helpful to get a very rough and ready estimate of this before making your enquiry.


The waterhead is the height difference between where the water would enter the hydro power system and it would leave it, measured in metres. Typically this could be the height of a weir or the vertical drop of water over a water wheel. If a waterwheel is an overshot type, the water head will be the same as the wheel diameter. If the site is undeveloped and has no old watermill structures present, then the potential head would be between where the hydro intake screen would be and where the water discharged from the turbine would return to the watercourse.

With hydro it is very important to get as much water head as you possibly can, as more water head means more power for not much more cost. Depending on how much water flow you have, the minimum amount of head required for a viable hydro system varies. If you have low waterhead and low waterflow, then installing a hydro system won’t be very cost effective. Typically a head in excess of 1m is the minimum requirement. Read More on How to Measure Water Head?

Water Flow (measuring water flow)

This the amount of water that can be passed through the turbine, measured in cubic meters per second. If is very difficult to work out how much water flow there is at a site, and establishing this forms a large part of the feasibility studies that we offer. The table below shows photographs of ‘typical’ rivers and streams to help you estimate how much water flow you have. You need to estimate the average annual flow, and not the flow on the wettest day of the year.Read More on How to Measure Water Flow?

River Categories

Category Example Description / Flow Minimum Head Needed
1  Very small stream Very small stream

0.01 m3/s to 0.05 m3/s

10m – 50m
2 Small Stream Small Stream

0.05 m3/s to 0.25 m3/s

2.5m – 10m
3 Stream Stream

0.25 m3/s to 1.00 m3/s

2 – 2.5m
4 Small River Small River

1.00 m3/s to 2.00 m3/s

1.5m – 2m
5 River 2.00 m3/s and greater River

2.00 m3/s and greater

1m – 1.5m

Once you’ve estimated the water head and the average water flow, you can estimate the power output as detailed below.


The maximum power of the hydro system can be roughly estimated as:

WaterHead X WaterFlow X 5 = kW

The waterhead is in meters and the waterflow in meters-cubed per second.

The micro-hydro power systems supplied by Hydro Generation typically range from 5kW – 250kW. A system smaller than 10kW however is unlikely to be cost effective.

Example 1

A River which is as large as the photo shown in Category 5 above.

Estimate the average waterflow rate to be 4 m3/s.

The waterhead at the site is 2 meters. Therefore the estimated power output would be:

Power (in kW) = WaterHead X WaterFlow X 5 = 2 (meters) x 4 (m3/s) x 5 = 40 kW

This is a reasonably good size for micro-hydro system.

Example 2

A fast-flowing stream in a back garden, but no significant drop apart from the slope of the land, which falls 2 metres over a 100m length.

From the table Category 1 above estimate the average waterflow rate at 25 liters/second (0.025 m3/s).

The power output would be:

Power (in kW) = WaterHead X WaterFlow X 5 = 2 (meters) x 0.025 (m3/s) x 5 = 0.25 kW

This is not enough power to make a micro-hydro project economically viable.

Micro hydro generator design

Any clients who provide us the waterhead and water flow data of their water site/micro hydro power plant
, we can design and calculate the right hydro turbine generators for them. The more detailed data, the more accurate for their hydro plant both the low head micro hydro generator and high head micro hydro generators.

What is head in hydro power plant?

When clients asked what is head in hydro power plant? we suggest them to Check our following hydro resources to know more about waterhead and waterflow and design information of a micro hydro power plant.

More Resources:

How to measure waterhead?
How to measure water low?
Micro Hydro Feasible Studies
Micro hydro power system design
Hydro turbine, hydro power generator Installation Process
Micro hydro power maintenance