Explanatory notes
Upstream (metres AOD)The level of the river upstream of the hydro plant is measured at (where?). AOD means ‘above ordnance datum’ which is a fixed reference level.
Downstream (metres AOD)The level of the river downstream of the hydro plant is measured at (where?). AOD means ‘above ordnance datum’ which is a fixed reference level.
Head (metres)This is the difference between the water levels, the distance that the water falls through the turbines. The upstream water has potential energy this is translated to kinetic energy in the form of rotation of the turbine as it falls through. This rotational energy is then converted to electrical energy through the generators.
Set levelWhen the upstream level of the river falls below this agreed level, the turbines are shut off and the hydro stops operating.
Above set level (metres) This is the difference between the upstream level of the river and the set level. This needs to be above zero for the hydro to operate.