Assessment of hydraulic conductivity in coastal floodplain acid sulphate soils on the north coast of NSW

Estuarine wetlands are characterised by complex interactions between vegetation type, surface water fluxes and porewater movement. Hydrology is a key determinate in species distribution, in wetland biomass productivity, nutrient cycling and availability. To be able to understand the intimate relationship between estuarine wetland ecology and hydrology, knowledge of wetland hydrology is critical if we are able to predict and manage change in wetland environments. These include both long-term gradual changes such as climate change and projected sea-level rise, and sudden changes resulting from human interference such as hydraulic modifications to drainage systems and or tidal flow (Hughes et al. 1998). Saturated hydraulic conductivity (Ksat) is a measure (quantitative expression) of a saturated soil’s ability to transmit water when subjected to a hydraulic gradient. Influences include gradients, soil ripeness, macropores, soil type, flow direction, flow rates. Ksat is a critical variable affecting the hydrology and acid export dynamics of drained acid sulfate soils (ASS). Assessment of Ksat in ASS is important in order to design appropriate management strategies for broadacre remediation projects. It has a controlling influence upon the lateral movement of solutes and rates of acidic groundwater drainage plus the behaviour of the groundwater table relative to adjacent drains (Cook et al. 1999; Cook and Rassam, 2002; Johnston et al. 2004).