Answer:
power generated = 117.72 MW
Step-by-step explanation:
given data 
flow rate of river = 240 m³/s
height above the surface lake = 50m 
solution 
we get power generated that is express as 
power generated = distance × acceleration due to gravity × elevation head × density of water ......1 
power generated = 240 × 9.81 × 50 × 1000
power generated = 117.72 MW