The hydrodynamics of the Bot River Estuary revisited

For the past 20 years management of the Bot/Kleinmond estuarine system in the south-western Cape has been based on the premise that, barring intervention, the estuary was naturally evolving into a freshwater coastal lake. This paper presents evidence, based on a 20-year series of water-level data, updated runoff estimates from the catchment and dimensional data, that, in the absence of anthropogenic influences, the system is not progressing naturally, but artificially, towards becoming a freshwater system. It is concluded that the increasingly closed state of the Bot Estuary in recent years is most likely due to reduction in runoff from its tributaries and premature artificial breaching of the Kleinmond arm of the system. These findings, coupled with the high conservation importance of the Bot River Estuary, suggest that the current management plan needs urgent revaluation and that the two estuaries cannot be managed separately. Key words: Bot River Estuary, estuary management, estuary breaching policy, closed estuary, estuarine dimensions, estuarine water levels, estuarine habitat Water SA Vol.31(1) 2005: 73-8