Historical trends in the flows of the Breede River

Abstract

The Breede River is not a large river by world standards, but is the largest in South Africa’s Western Province, and plays a significant part in the province’s economy. Models predict that flows into it could be seriously affected by climate change. Accordingly a study was made of trends in flow over recent decades, in the hope that any trends detected would confirm, or otherwise, the prediction of the models. Data on flows over 30 years at various sites in the Breede Valley were downloaded from the Department of Water Affairs. The data were first checked for consistency. In 2 cases there was evidence that behaviour of the flow had changed, apparently permanently, during the course of the study period (typically the variance of the flow had changed markedly at a particular point in time). The data series was accordingly truncated to make use only of the longest series of consistent records. A simple, robust technique was then employed to detect the trends.

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