SYNOPSIS OF THE IMPACT OF ARTIFICIALLY OPENING THE MOUTH OF THE BOT RIVER ESTUARY: IMPLICATIONS FOR MANAGEMENT

SUMMARY

This paper synthesizes previous research on the Bot River estuary, including that on its past and present geology, sedimentology, hydrology, history, plant life, invertebrates, birds and fish. The estuary is periodically breached to form a deep mouth and this restores estuarine conditions and allows recruitment of fish; but it also disrupts the system and results in massive losses of aquatic weeds and invertebrates, and a twentyfold reduction in bird-life.

A key feature in the ecology is that the Bot is connected to the adjacent Kleinmond estuary by overflow channels which act as a spillway when water-levels in the Bot are high. Because of this the Bot will slowly become diluted by river-water and change into a fresh-water lake if it is not breached.

Six proposed plans for the management of the Bot River estuary are discussed. Only two are viable: either the estuary should never be breached (and thus be managed as fresh-water lake) or breaching should be controlled and undertaken about every three or four years or when salinities drop below 6‰ (and the system managed as an estuary).