Surge Studies for Portage Mountain Tailrace System

by Kenneth C. Wilson,

Serial Information: Journal of the Power Division, 1969, Vol. 95, Issue 1, Pg. 1-16

Document Type: Journal Paper


The discharge of the underground powerhouse at Portage Mountain rejoins the Peace River through two large free-flow tunnels. The surge waves in these tunnels caused by changes in turbine discharge were studied by three methods—approximate manual calculations, computer analysis, and model testing. The surges are considered under two headings—the determination of the initial extreme level following a flow change and the more complicated conditions occurring after the return of surge waves reflected at the tunnel exit. The procedures used for the manual and computer calculations are based directly on the momentum and continuity relationships, because the great variation in surface breadth with water level precludes the use of standard methods for surges in open channels. On the other hand, the tunnels may be considered hydraulically short and this permits the actual configuration to be approximated by a level tunnel with friction losses lumped at the entrance and exit. Comparison of the results of the three methods of surge study indicates very satisfactory agreement.

Subject Headings: Tunnels | Computer analysis | Computer models | Comparative studies | Water discharge | Underground structures | Power plants | Mountains

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