Influence of the Pacific Decadal Oscillation and El Niño Southern Oscillation on Operation of the Capilano Water Supply Reservoir, Vancouver, British Columbia

Abstract

The magnitude and duration of low reservoir inflows in the summer and early fall are critical for water supply planning and operations for the Greater Vancouver Regional District (now Metro Vancouver). The influence of climate fluctuations on summer and fall reservoir inflows was investigated and a reservoir operation model developed to simulate Capilano Reservoir operations. Flow records for the gauge on the Capilano River above Intake were adjusted to account for releases from the upstream Palisade Lake. It was found that reservoir inflows for the June to September period are affected by the El Niño Southern Oscillation (ENSO) and the Pacific Decadal Oscillation (PDO). The 15 lowest June to September inflows over the period of gauge records have all been associated with warm or neutral ENSO conditions typically combined with warm or neutral PDO conditions. Annual reservoir drawdown, defined as the annual extended period of no spill, was used as an indicator of stress on reservoir operations. Simulation of reservoir inflows and outflows from 1914 to 2005 showed that the longest reservoir drawdown durations were almost always associated with warm ENSO and warm PDO conditions. The shortest periods of drawdown were normally associated with both cool ENSO and cool PDO conditions. Due to the storage effects, reservoir drawdown is a good indicator of periodic climate variations because of amplification, similar to the sensitivity of glaciers to climate episodes. © 2008, Taylor & Francis Group, LLC.