II.9.3 - Multiple Powerhouses

Fig. 59 Multiple powerhouse configuration showing allocation of spill and powerhouse flows.

In these cases, flow is allocated fractionally as follows:

• Flows are first allocated to planned spill in fish passage hours.
• Remaining flow is partitioned between the primary and secondary powerhouses and additional spill as follows:

• Operate highest priority powerhouse up to its hydraulic capacity.
• Spill water up to another level called the spill threshold.
• Above the threshold, use the second powerhouse.
• Over the second powerhouse hydraulic capacity, spill extra flow.

Fig. 60 Flow allocation through two powerhouse projects.

An example of flow allocations is described as follows (Fig. 60):

• At level 4 units of flow are put to Fish Spill and 2 units are put through the First Powerhouse.
• At level Fish Spill has four units of flow, the First Powerhouse is run at its hydraulic capacity, which is 4 flow units, and the spillway has 3 units of additional spill.
• At level the First Powerhouse is at hydraulic capacity, spill flow includes Fish Spill and additional spill up to the Spill Threshold and 2 units of flow pass the Second Powerhouse.