Assessing the power potential of your river

The power available from your river is a function of the flow of water and the drop (head).  We were able to get estimates of flow from the Environment Agency but there are formulas for estimating flows over a weir that are a function of the width of the weir and the height of water over the weir's edge.  The estimates suggested that the flow would exceed 1 m³/sec for c.66% of the year and this was used as the flow to size the system.  With 1.0 m³/sec of flow,  an effective head of 1.5m and allowing for 75% efficiency factor indicated a power potential of 11KW 

 Power
=
Head (m) x Water flow (m³/sec)
 x
Water density (kg/m³) x 9.81 (coefficient of gravity)
=
  1.5m x 1.0 m³/sec x 1000 x 9.81 x 75% efficiency
  =
11 KW

Potential to serve 14 average homes...

Allowing for 70% efficiency factor implies...
Potential for 70,000 KWhr per year or electricity consumption of 14 average homes