Effect of discharges on the effectiveness of the Cox Creek wetland system, South Australia

Abstract

Intensive agriculture activities apply inorganic fertilisers to improve crop productions. However, exceeded fertiliser applications above crop requirements at the upper Cox Creek sub-catchment, South Australia have increased the potential of excess nutrients to be mobilised during runoff events. The variability in the Cox Creek stream flows have important implications in terms of changes in the overall loads of pollutants and their distribution along the stream and consequently to the downstream reservoir, Mount Bold. Therefore, this study aims to assess the performance of the Cox Creek wetland in reducing nutrient loads from the Cox Creek to downstream water bodies. Six different flow rate classes were distinguished based on daily flow data from January 2004 to December 2009. The greatest number of days were recorded within 0-1 ML day-1 flow class represented very dry flow class and indicated the lowest amount of flow rates. In contrast, the lowest numbers of days were recorded within 46-300 ML day-1 flow class represented high flow class and indicated the highest flow rates. The flow classification corresponding to annual catchment load reveals the importance of the Cox Creek wetland to retain water, particularly during high flow events.