Freshwater requirements of Knysna Estuary

Haw, Peter Macauly

Freshwater requirements of Knysna Estuary

Master Thesis

1984

Abstract

The hydrology of the 335 km 2 catchment of the Knysna River is described using several standard techniques, including those described in Hydrological Research Unit Reports Nos 2/76, 1/72 and 2/78. The mean annual . 6 -1 run-off at the farm Charles ford is about 61 x 10 m3 an. . Salinity measurements were made at various stations between January and June 1984. These data were used to calibrate and verify a 1-dimensiona~ mathematical model of the Knysna Estuary. The model showed that the salinity would rise to 36 parts per thousand at the Old Drift if the · river flow was stopped altogether. The model also shows that salinities drop to 1 or 2 parts per thousand at the National Road Bridge for three successive tides following a one-in-two-year flood -1 ( 40 m 3 s ) • The response of the biota to changing salinities is described using available literature. It appears that there will be a gradual decline in primary and secondary productivity if the river flow is reduced. Other management approaches to this problem as well as the ethical problem of reducing the freshwater inflow into an estuary are explored.

Keywords

Hydrology

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