Hydrology, Water Quality and Management Strategies of a Coastal Floodplain Wetland, New South Wales, Australia

Abstract

Many coastal floodplain wetlands in northern NSW have been drained and fitted with one-way floodgates. These wetlands are often underlain by acid sulfate soils (ASS) that can release acidic by-products into the groundwater and surface water if oxidised. Little Broadwater, on the Clarence River, is typical of these altered wetlands. An ongoing restoration trial focussing on increased tidal exchange, initiated in June 2003, provided the opportunity to study the rehabilitation process taking place within the wetland. This study aimed to investigate the hydrology and changes in water quality characteristics during the reestablishment of tidal exchange at Little Broadwater. Discharge water quality (pH, electrical conductivity (EC) and dissolved oxygen (DO)) were compared pre- and post-rehabilitation to determine if restoring tidal exchange improved discharge water quality. Monitoring of surface water and groundwater quality (pH, EC, DO, temperature, acidic cations, basic anions, total nitrogen and total phosphorus) was conducted over a 28-month period. Short-term monitoring was also conducted at two reference wetlands to compare spatial patterns and factors that affected water quality. The results of this study were used to develop a conceptual model of coastal floodplain wetland functioning, with particular reference given to Little Broadwater.