THE HYDROLOGY OF THE BOT RIVER ESTUARY

Abstract

SUMMARY During the flood year of 1981 and in 1983 the Bot River estuary, one of the largest lagoons in the south-western Cape was opened to the sea by three artificial breachings of the sand bar which were aimed at lowering the excessively high water levels in the lagoon and at the re-establishment of estuarine conditions. Surveys were undertaken in the lagoon and at the mouth channels in an attempt to formulate a future viable management policy, taking into account the conflicting interests of the defenders of continued artificial breachings and of those who advocate a closed estuary which, if left unbreached, will eventually change into a coastal fresh-water lake. Artificial breachings cause a rapid lowering of the water-level in the vlei associated with the sudden loss of large areas of water surface; they also lead to the effective discharge of silt-laden flood waters and an influx of clear sea-water. It is recommended that breachings only be done after the vlei has reached a water-level of more than ...