Seiches and Set-up on Lake Winnipeg

Abstract

Recorder charts of water level for the ice-free season are examined for six stations on Lake Winnipeg for the years 1961-1964. Transverse and longitudinal seiches are identified for the north and south basins. An interference pattern is noted for seiches over two different fetches at Victoria Bench. Typical weather situations producing transverse and longitudinal seiches are identified. Moderate to large set-up is examined for 37 cases and geostrophic winds scaled off from weather charts covering an 18-hr period preceding the peak set-up. Using corrections for curvature, motion of the pressurc system, deviation from the main axis of the lake, and air stability, an assumned over-water component is computed for each case. The correlation between set-up and over-water wind square is found to be 0.81. Standard deviation of actual set-up from that predicted by the regression equation is 0.076 m.