Tidal and subtidal water level fluctuations in the Berg Estuary

Abstract

Ocean tide gauge data from Saldanha Bay, and water levels from Laaiplek, Kliphoek and Jantjiesfontein in the Berg Estuary are analysed to determine amplitude and propagation characteristics at the M₂ semidiurnal frequency, the K₁ diurnal frequency and subtidal fluctuations in the so-called ‘weather band’. Visual and spectral analysis techniques are used, and show that the M₂, K₁ and subtidal signals propagate at different speeds in the estuary, while the tidal signals are also attenuated substantially with respect to the subtidal signal at the upper end of the estuary (60 km). A model with friction is developed to explain the dynamics, and relatively good agreement is found with the measured results.

Key words:

• Berg Estuary
• water levels
• tidal
• subtidal