DEPARTMENT OF PRIMARY INDUSTRIES Salt movement in a groundwater re-use system based on a ‘tree plantation’. A. Terry* , B. Selle and B. Gill PIRVic, DPI Victoria, Private Bag 1 Ferguson Road, Tatura, Vic 3616, AUSTRALIA, *Alister.Terry@dpi.vic.gov.au Key Results Background/Introduction The ‘Mt. Scobie partial conjunctive re-use pilot site’ was established in December 1998 and is located approximately 11 km southwest of Kyabram in north central Victoria, Australia. Dairy farming is the main enterprise on the property, which covers a total area of some 400 hectares. The farm has been operated in a manner consistent with local ‘Land and Water Management Plan’ guidelines and the landholder has managed the site as part of their daily operations. The key objectives for this project are: To develop and implement a system to test the potential of integrating, the disposal of high salinity groundwater to an ‘in situ’ ‘salt tolerant’ tree plantation, into a productive dairy farming system. To determine whether such a system, once established and operating, is able to maintain a long term salt balance where the rootzone salinity across the property, decreases or remains at a level where there is no decline in the prosperity of the property. Salt input Salt leaching Change in salt storage Biophysical System Soil Salinity has been increasing under the trees. Soil salinity has been stable or decreased across the remainder of the farm. Both the volume and salinity of the water applied to the trees has increased. Trees The trees used in the plantation include a species-provenance salinity resistance trial of Casuarina cunninghamiana, Casuarina glauca and Eucalyptus occidentalis. A separate field trial of eucalypt hybrids produced under the Xylonova Research and Development Program is also being run at the project plantation site. Proposed System Operation Pumping test results on the aquifer predicted a maximum annual volume of 60ML @ 10 dS/m. 35 ML would be conjunctively re-used (mixed with fresh surface supply water), for irrigation of pasture and 25ML for irrigation of the tree plantation. Actual System Operation The site operated initially as outlined above, the trees at the site established well and groundwater pumping and disposal to the tree site initially occurred as planned. Low surface water availability over the past 5 years has resulted in a higher volume of groundwater to be applied to the tree block. The increase in soil salinity is a result of the increased volumes applied and not the increased salinity of the applied water. Leaching has increased below the trees but not enough to compensate for the added salt. Recommendations/Future Work Continue monitoring to determine if the system can reach an equilibrium where salt in equals salt out. Develop a model of the system to determine if and when this point may be reached, and what changes can be made to the system to ensure that this happens before soil salinity levels reach critical levels for the trees © State of Victoria, Department of Primary Industries 2008. This publication is copyright. No part may be reproduced by any process except in accordance with the provisions of the Copyright Act 1968. Disclaimer: This publication may be of assistance to you but the State of Victoria and its employees do not guarantee that the publication is without flaw of any kind or is wholly appropriate for your particular purposes and therefore disclaims all liability for any error, loss or other consequence which may arise from you relying on any information in this publication. Authorised by the Victorian Government, Department of Primary Industries, Ferguson Road, Tatura.Printed by Department of Primary Industries, Ferguson Road, Tatura, 2008.