Tidal, Meteorological and Hydrological Effects on the Water Level Variation in a Lagoon, Lake Shinji

Abstract

The characteristics of water level variation in Lake Shinji are reported in comparison with the sea level variation at Sakai. Spectral analysis by the fast Fourier transform method, using hourly data of 355 days shows that semi-diurnal and diurnal variations in Lake Shinji are not due to direct water transport from adjacent Lake Nakanoumi through the Ohashi River, but rather to tidal waves damped and distorted through the Ohashi River channel. This analysis also indicates that water level variations over periods of 4-8 days are predominant in Lake Shinji under low freshwater input, and are similar to the 25hour moving mean variation of water level at Sakai. The moving mean water level fluctuated following a temporal variation in atmospheric pressure due to the passage of typhoons in the Japan Sea. Hence, the water level variation in Lake Shinji is not determined by the tide, but by meteorological events in combination with the freshwater inflow. © 1993, The Japanese Society of Limnology. All rights reserved.