Influence of wind on water levels and lagoonriver exchange in the River Murray, Australia

Abstract

This paper examines river water levels and water exchange between the river and an adjacent lagoon at a site on the River Murray about 150 km from its discharge point into Lake Alexandrina. Riverine water levels at the site underwent significant fluctuations (~ 0·3 m) which appeared to be mainly associated with fluctuations in the N–S component of wind rather than with discharge.

The lagoon studied was connected by a channel to the river. The measured flow through the channel was almost always out and had an average rate over the 30 days of the study which was large enough to empty the lagoon in 9 days. It is hypothesized that the replenishment flow to the lagoon occurred as a seeping flow through the bank separating the lagoon from the river. Successful comparisons between measurements and computer simulations of river water level and of the flow through the channel confirmed that it was the wind stress acting on the surface that mediated variations in riverine water levels and the exchange between river and lagoon.