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WSN - Castlereagh Waste Disposal Project

Our aim is to evaluate how a mixture of native woody species and grasses can be used to minimize the risk of contamination of water systems as a result of deep drainage and run-off from waste disposal sites. Absence of vegetation during site preparation leads to saturation of the upper soil profile, with excess water draining into the groundwater (also called deep drainage), taking contaminants with it. Similarly, during the early phases (several years) of revegetation, rainfall exceeds the ability of vegetation to transpire and excess water can drain through the waste material, leaching toxic material into the water table. This study will determine the efficacy of using vegetation to minimise deep drainage and thereby minimise off-site effects.

For most of us the weekly garbage collection is a necessary but annoying ritual and as long as the waste we generate disappears it’s a case of “out-of-site-out-of-mind”. For local and state governments ,however ,the disposal of waste to landfills and the potential for contaminants to leach into groundwater can be a recurring nightmare. Scientists in the UTS Plant Functional Biology and Climate Change Cluster (C3) believe that a five year project, into minimising the risk of contamination of water systems from waste disposal sites, will provide valuable data to help manage these sites, protect the environment and adjacent communities. Jointly funded by ARC and WSN the project is using recent advances in sensing technology to evaluate how a mixture of native woody species and grasses can be used to rehabilitate the Castlereagh Waste disposal site in Sydney’s north west.

Landfill sites are typically a series of deep “cells” dug into the ground. Once full, each cell is capped with clay and topped with a layer of soil. However, the absence of vegetation during site preparation, followed by several years of early growth, can lead to saturation of the upper layers of the soil profile, with excess water draining into the groundwater, taking contaminants with it.

Professor Derek Eamus leads the Terrestrial Ecohydrology Research Group (TERG) within C3 and it is his team of researchers, including Dr Isa Yunusa, Dr Daniel Taylor, Dr Cate Macinnis-Ng, Dr Zheng Li and Dr. Melanie Zeppel, who have developed the expertise needed to get the data to answer the question: can revegetation successfully minimise deep drainage. A combination of field research and modelling is being applied to this project

The researchers will be using new sensors that measure very low sap flow, a technique they have perfected as part of a large, collaborative project known as the Hawkesbury Forest Experiment.
They will also be monitoring groundwater levels and the soil moisture content at various depths within the cells using piezometers and neutron probes. These data will be used to get an accurate picture of the water balance. To-date, it looks as though mature woodlands do indeed minimise deep drainage and therefore can minimise the risk of leaching from the waste site. This information is of particular interest to the local community who fear that contamination of their local water table will occur.

Experimental set-up at WSN

The top image shows researchers drilling trees to attach sensors.

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