Hydraulic Transient Study of Mainstream Tunnel System and Control System

Numerical studies of hydraulic transients for the TARP Phase I system were conducted in 1988 and 1992. These studies revealed that due to storage and/or conveyance limitations of the TARP Phase I Mainstream system using the Keifer/Song maximum hydrograph, inflow must be substantially reduced to avoid geysering problems induced by hydraulic transients. In order to improve the hydraulic transient condition, TARP Phase II has been proposed to add additional water storage and increase the conveyance ability. A hydraulic transient study for the TARP Phase II system was also conducted recently. However, before the TARP Phase II is completed, a reasonable tunnel operation method for the current TARP Phase I system must be sought to minimize the potential of the hydraulic transient problems. This study is to investigate the extent and nature of hydraulic transients in the current TARP Phase I Mainstream tunnel under the existing flow control structures for different hydrographs.