Hydropower
Environmental Engineering · FE Reference Handbook section
Core formulas for this FE topic
Definitions, applicability, units, assumptions and worked examples for each relation.
Worked exam-style examples
The four ways this section is written on the real exam — thoughts first, then equations, then substitution.
hydropower generation output for a dam with a given head and flow Given turbine efficiency (eta) = 0.7000; water density (rho) = 995.0 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; flow rate through turbine (Q) = 95.0000 m^3/s; hydraulic head (H) = 29.0000 m, determine the hydropower output (P) in W.
Given
Find
hydropower output (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: turbine efficiency (eta) = 0.7000, water density (rho) = 995.0 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, flow rate through turbine (Q) = 95.0000 m^3/s, hydraulic head (H) = 29.0000 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 18,823,992 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 37,647,984 — kept a factor of two that cancels in the correct rearrangement.
- 9,411,996 — dropped that same factor in the other direction.
- 20,706,391 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
hydropower plant power output calculation from turbine efficiency Given turbine efficiency (eta) = 0.7200; water density (rho) = 997.0 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; hydraulic head (H) = 178.0 m; hydropower output (P) = 42,721,900 W, determine the flow rate through turbine (Q) in m^3/s.
Given
Find
flow rate through turbine (Q), in m^3/s
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except Q is given, so isolate Q symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q:
Step 3 — List the givens: turbine efficiency (eta) = 0.7200, water density (rho) = 997.0 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, hydraulic head (H) = 178.0 m, hydropower output (P) = 42,721,900 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Q = 34.0827\ \text{m^3/s}Step 6 — Check: returning Q = 34.0827 m^3/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 68.1654 — kept a factor of two that cancels in the correct rearrangement.
- 17.0413 — dropped that same factor in the other direction.
- 37.4910 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
run-of-river hydropower output estimate Given turbine efficiency (eta) = 0.8600; water density (rho) = 993.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; flow rate through turbine (Q) = 207.0 m^3/s; hydropower output (P) = 285,047,900 W, determine the hydraulic head (H) in m.
Given
Find
hydraulic head (H), in m
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except H is given, so isolate H symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for H:
Step 3 — List the givens: turbine efficiency (eta) = 0.8600, water density (rho) = 993.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, flow rate through turbine (Q) = 207.0 m^3/s, hydropower output (P) = 285,047,900 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning H = 164.3 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 328.6 — kept a factor of two that cancels in the correct rearrangement.
- 82.1452 — dropped that same factor in the other direction.
- 180.7 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
hydropower generation output for a dam with a given head and flow Given turbine efficiency (eta) = 0.8500; water density (rho) = 990.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; flow rate through turbine (Q) = 470.0 m^3/s; hydraulic head (H) = 40.0000 m, determine the hydropower output (P) in W.
Given
Find
hydropower output (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: turbine efficiency (eta) = 0.8500, water density (rho) = 990.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, flow rate through turbine (Q) = 470.0 m^3/s, hydraulic head (H) = 40.0000 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 155,274,544 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 310,549,088 — kept a factor of two that cancels in the correct rearrangement.
- 77,637,272 — dropped that same factor in the other direction.
- 170,801,998 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
hydropower plant power output calculation from turbine efficiency Given turbine efficiency (eta) = 0.7500; water density (rho) = 991.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; hydraulic head (H) = 192.0 m; hydropower output (P) = 82,389,700 W, determine the flow rate through turbine (Q) in m^3/s.
Given
Find
flow rate through turbine (Q), in m^3/s
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except Q is given, so isolate Q symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q:
Step 3 — List the givens: turbine efficiency (eta) = 0.7500, water density (rho) = 991.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, hydraulic head (H) = 192.0 m, hydropower output (P) = 82,389,700 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Q = 58.8232\ \text{m^3/s}Step 6 — Check: returning Q = 58.8232 m^3/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 117.6 — kept a factor of two that cancels in the correct rearrangement.
- 29.4116 — dropped that same factor in the other direction.
- 64.7055 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
run-of-river hydropower output estimate Given turbine efficiency (eta) = 0.8700; water density (rho) = 998.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; flow rate through turbine (Q) = 271.0 m^3/s; hydropower output (P) = 51,896,400 W, determine the hydraulic head (H) in m.
Given
Find
hydraulic head (H), in m
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except H is given, so isolate H symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for H:
Step 3 — List the givens: turbine efficiency (eta) = 0.8700, water density (rho) = 998.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, flow rate through turbine (Q) = 271.0 m^3/s, hydropower output (P) = 51,896,400 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning H = 22.4715 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 44.9430 — kept a factor of two that cancels in the correct rearrangement.
- 11.2357 — dropped that same factor in the other direction.
- 24.7186 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
hydropower generation output for a dam with a given head and flow Given turbine efficiency (eta) = 0.7700; water density (rho) = 990.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; flow rate through turbine (Q) = 423.0 m^3/s; hydraulic head (H) = 154.0 m, determine the hydropower output (P) in W.
Given
Find
hydropower output (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: turbine efficiency (eta) = 0.7700, water density (rho) = 990.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, flow rate through turbine (Q) = 423.0 m^3/s, hydraulic head (H) = 154.0 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 487,388,526 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 974,777,051 — kept a factor of two that cancels in the correct rearrangement.
- 243,694,263 — dropped that same factor in the other direction.
- 536,127,378 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
hydropower plant power output calculation from turbine efficiency Given turbine efficiency (eta) = 0.8500; water density (rho) = 996.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; hydraulic head (H) = 43.0000 m; hydropower output (P) = 177,163,800 W, determine the flow rate through turbine (Q) in m^3/s.
Given
Find
flow rate through turbine (Q), in m^3/s
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except Q is given, so isolate Q symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for Q:
Step 3 — List the givens: turbine efficiency (eta) = 0.8500, water density (rho) = 996.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, hydraulic head (H) = 43.0000 m, hydropower output (P) = 177,163,800 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Q = 495.8\ \text{m^3/s}Step 6 — Check: returning Q = 495.8 m^3/s to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 991.7 — kept a factor of two that cancels in the correct rearrangement.
- 247.9 — dropped that same factor in the other direction.
- 545.4 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
run-of-river hydropower output estimate Given turbine efficiency (eta) = 0.8000; water density (rho) = 991.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; flow rate through turbine (Q) = 400.0 m^3/s; hydropower output (P) = 97,180,700 W, determine the hydraulic head (H) in m.
Given
Find
hydraulic head (H), in m
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except H is given, so isolate H symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for H:
Step 3 — List the givens: turbine efficiency (eta) = 0.8000, water density (rho) = 991.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, flow rate through turbine (Q) = 400.0 m^3/s, hydropower output (P) = 97,180,700 W.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning H = 31.2225 m to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 62.4451 — kept a factor of two that cancels in the correct rearrangement.
- 15.6113 — dropped that same factor in the other direction.
- 34.3448 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower
hydropower generation output for a dam with a given head and flow Given turbine efficiency (eta) = 0.8800; water density (rho) = 996.5 kg/m^3; gravitational acceleration (g) = 9.8100 m/s^2; flow rate through turbine (Q) = 9.0000 m^3/s; hydraulic head (H) = 87.0000 m, determine the hydropower output (P) in W.
Given
Find
hydropower output (P), in W
Start with the thinking
- The governing relation printed in this handbook section is Hydropower.
- Everything except P is given, so isolate P symbolically first — never rearrange after the numbers are in.
- Tabulate each given with its unit and confirm the units are consistent with the relation before substituting.
- Hydropower output from a dam or run-of-river plant depends on turbine efficiency, flow rate, and hydraulic head.
Step-by-step solution
Step 1 — State the governing relation:
Step 2 — Rearrange symbolically for P:
Step 3 — List the givens: turbine efficiency (eta) = 0.8800, water density (rho) = 996.5 kg/m^3, gravitational acceleration (g) = 9.8100 m/s^2, flow rate through turbine (Q) = 9.0000 m^3/s, hydraulic head (H) = 87.0000 m.
Step 4 — Substitute the given values:
Step 5 — Evaluate:
Step 6 — Check: returning P = 6,735,824 W to
reproduces the given quantities, and both sides carry the same units.
Why the other options are there
- 13,471,648 — kept a factor of two that cancels in the correct rearrangement.
- 3,367,912 — dropped that same factor in the other direction.
- 7,409,407 — rounded an intermediate value before the final step.
Reference: FE Handbook — Hydropower