The figure below shows that model schematic.

The next figure shows the outlets. You can see that the only outlet is a power plant.

The power equation is as follows:

Power in megawatts (mw) = Q*w*h*e/737,560

where Q is in cfs, w is weight of water in lb/ft^3, h is head differential in feet, e is efficiency

Note that 737,560 ft-lbs/sec = 1 megawatt

Understanding the variables that go into the power equation will help with the understanding of the tabs used to describe the power plant.

The outlet tab specifies the hydraulic capacity of the power plant. In this case, the hydraulic capacity is set to 5,000 cfs for all elevations.

The capacity tab specifies the generating capacity of the power plant. The purpose of this tab is to limit the computed power generation to no more than the actual generating capacity. In this case, I set the maximum generating capacity to 10 mw.

For the efficiency tab, I set the value to a constant 80%.

Station use is for internal use at the dam. This value is often set to zero; however, I put in 500 cfs to show its impact. The value that is used for station use is passed through the outlet, but it is not used in the power computation.

The final tab is hydraulic losses. This reflects the losses associated with the power plant. The amount used for hydraulic losses is subtracted from the total head difference computation. For this example, I used a constant loss of 2 feet.

The head differential is computed as the difference between the headwater and tailwater. The headwater is computed as the pool elevation at each time step. For this simulation, the top of conservation (50 ft) is held for the entire simulation. For ease of computation, a constant tailwater elevation of 25 ft is used. This leads to a head differential of 25 ft.

The figures below show the top of conservation elevation and the tailwater definition.

The next figure shows the pool elevation and outflow results at the reservoir. Note that the pool elevation is held constant at 50 ft while the outflow is held constant at 5,000 cfs. Recall that there is only one outlet so all outflow is going through the power plant.

The power computation at all time steps is as follows:

Q = 5,000 - 500 = 4,500 cfs (note that 500 cfs is subtracted due to station use)

w = 62.4 lb/ft^3

h = 25 - 2 = 23 ft (2 is subtracted due to the hydraulic losses)

e = .80

Power (mw) = (4,500 * 62.4 * 23 * .80) / 737,560 = 7 mw

Since the generating capacity of 10 mw is not exceeded, the computed generation amount of 7 mw will not be limited.

The power generation plot is shown below. The upper plot shows a constant 7 mw of power generation. The bottom plot shows 5,000 cfs flowing through the power plant with 4,500 cfs of that flow used for power generation.