The Berg Estuary: Water structures and dynamics

Abstract

Regular quarterly measurements were made in the Berg Estuary over a period of three years from 2002 to 2005. These are analysed with other available time series data to provide a detailed description of the water structures and dynamics of the estuary. The measurements allow some assessment of variability in the estuary on interannual, seasonal, monthly, daily and hourly time scales. The winter spates of fresh water inflow are the major influence on estuarine structures, and even though the measurements were taken during a particularly dry period, peak flows of 120 m³/s were still sufficient to flush out the summer build-up of high-salinity oceanic water. The seasonal effect is also evident in water temperature, dissolved oxygen, pH and turbidity sections. Very little vertical structure was observed, the estuarine water being essentially well-mixed at all times, and this means that there was little evidence of the build-up of anoxic bottom water. It is recommended that some future monitoring continue to assess longer-term trends, and the impact of the new Berg River Dam.

Key words:

• Berg Estuary
• water structure
• salinity
• temperature
• dissolved oxygen
• pH
• turbidity