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→Measuring the flow of the water energy source
The hydrological data may be essential for the design of the proposed small hydroelectric plant. A lack of flow, and thus shortage of water, will lead to disillusionment when the installation is working due to the large gap between the expected power output and true available power. There is no need to seek accurate hydrological data if the power output of the proposed installation is well below the maximum power usage of the site chosen for the project. Given that the turbine is to be placed near the river, it is highly desirable to know the variations of water level to avoid seeing water invading the facilities during floods.
====Measuring the flow
of the water energy source==== Depending on whether the stream runs horizontal, or whether it comes from a hill, more "head" is available, which means that we can use different types of water wheels or hydroelectric turbines. Head is the difference in elevation between the point where you start capturing the water (beginning of stream or water diversion) and where you start the use it (where the hydroelectric system is set up). Systems requiring a high head include: Pelton and Turgo turbine, and backshot and overshot water wheels. Systems that require little head and a high flow are Crossflow turbines and breastshot water wheels. Finally, when there is no head available whatsoever (horizontal stream), a undershot water wheel can be used.<ref>Practical self-sufficiency by Dick and James Strawbridge</ref>
In order to
asses the amount of flow and head available, it is necessairy to measure it. The height elevation can be measured using measuring tap or a height meter. The flow can be measured by building a temporary dam with a pipe. By then filling a container with a known volume while measuring the time required for this with a stopwatch, we know the flow.
== Mechanical power ==