Assessment of salinity management options for Kyeamba Creek, New South Wales: DATA ANALYSIS AND GROUNDWATER MODELLING Richard G. Cresswell, Warrick R. Dawes, Greg K. Summerell, Glen R. Walker Landscapes & Industries KNOWLEDGE Assessment of salinity management options for Kyeamba Creek, New South Wales: DATA ANALYSIS AND GROUNDWATER MODELLING Richard G. Cresswell, Warrick R. Dawes, Greg K. Summerell, Glen R. Walker Authors: Richard G. Cresswell 1, Warrick R. Dawes 2, Greg K. Summerell 3,4,5, Glen R. Walker 6, 7 1. Bureau of Rural Sciences, Canberra, ACT 2. CSIRO Land and Water, Canberra, ACT 3. Centre for Natural Resources, NSW Department of Land and Water Conservation, Wagga Wagga, NSW 4. CRC for Catchment Hydrology, Canberra, ACT 5. University of Melbourne, Melbourne, Victoria 6. CSIRO Land and Water, Adelaide, SA 7. Rural Solutions SA, Adelaide, SA CSIRO Land and Water Technical Report 26/03 CRC for Catchment Hydrology Technical Report 03/9 MDBC Publication 12/03 Published by: Murray-Darling Basin Commission Level 5, 15 Moore Street Canberra ACT 2600 Telephone: (02) 6279 0100 from overseas + 61 2 6279 0100 Facsimile: (02) 6248 8053 from overseas + 61 2 6248 8053 Email: [email protected] Internet: http://www.mdbc.gov.au ISBN: 1 876 830 52 2 Cover photo: Arthur Mostead Margin photo: Mat Gilfedder © 2003, Murray-Darling Basin Commission and CSIRO This work is copyright. Photographs, cover artwork and logos are not to be reproduced, copied or stored by any process without the written permission of the copyright holders or owners. All commercial rights are reserved and no part of this publication covered by copyright may be reproduced, copied or stored in any form or by any means for the purpose of acquiring profit or generating monies through commercially exploiting (including but not limited to sales) any part of or the whole of this publication except with the written permission of the copyright holders. However, the copyright holders permit any person to reproduce or copy the text and other graphics in this publication or any part of it for the purposes of research, scientific advancement, academic discussion, record-keeping, free distribution, educational use or for any other public use or benefit provided that any such reproduction or copy (in part or in whole) acknowledges the permission of the copyright holders and its source (‘Assessment of salinity management options for Kyeamba Creek, New South Wales: Data analysis and groundwater modelling’) is clearly acknowledged. To the extent permitted by law, the copyright holders (including its employees and consultants) exclude all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this report (in part or in whole) and any information or material contained in it. The contents of this publication do not purport to represent the position of the Murray-Darling Basin Commission or CSIRO in any way and are presented for the purpose of informing and stimulating discussion for improved management of Basin's natural resources. Acknowledgements This report represents a synthesis of information garnered from a wide spectrum of work performed on a relatively small catchment within the Murrumbidgee River system. This report places Kyeamba Creek into the context of Catchment Characterisation, with emphasis on the salinity perspective as outlined by Coram (1998) and Coram et al. (2000). The Catchment Characterisation Framework was made possible through the concerted efforts over many years of local and regional hydrogeologists who first developed and populated the concept from a dryland salinity perspective. Many of these are mentioned in Coram (1998), and have contributed to various aspects of this and other work over a period of years. This report draws on the vast store of knowledge held in the archives and minds of people within the institutions listed with the authors. In particular, this report draws on work carried out for local Landcare and communities by Department of Land and Water Conservation staff, particularly Don Woolley, Darice Pepper, Frank Harvey and Hugh Jones, and by former Australian Geological Survey Organisation (now Geoscience Australia) staff, particularly Jim Kellett (now with Bureau of Rural Sciences) and Phil Bierworth. This work was funded under the Murray-Darling Basin Commission’s Strategic Investigations and Education Program, Grant Number D9004: ‘Catchment characterisation and hydrogeological modelling to assess salinisation risk and effectiveness of management options’. This report has benefited immensely from reviews from Ray Evans and Jai Vaze, and from numerous discussions with other members of the Catchment Characterisation project. Editorial support from Mat Gilfedder and Pauline English (CSIRO Land and Water) is gratefully appreciated. i CATCHMENT CHARACTERISATION, KYEAMBA CREEK CASE STUDY Executive summary Introduction Kyeamba Creek is represented as Intermediate and Local Flow Systems in Kyeamba Creek catchment, located within fractured rock aquifers (Palaeozoic the uplands of the Lachlan Fold Belt of fractured rock in the Coram et al. 2000 south-eastern Australia, comprises an classification). Suggested management intermediate-scale fractured rock aquifer with options for this type of flow system include overlying alluvial fill in drainage lines and revegetation/reafforestation of upper depressions. This study of the catchments using perennial pastures, hydrogeological factors influencing salinity in native pasture, and native trees, possibly the Kyeamba catchment was undertaken to: with some groundwater pumping applications (Coram et al. 2000). These • describe the physical setting and systems commonly have only a small condition of the Kyeamba Creek proportion of land area actually salinised, catchment and aquifer system less than two percent, but can be a major • examine various data interpretations source of salt via saline discharge to on the conceptual model of flow streams and larger river systems. processes for recharge and discharge Discharge typically occurs at breaks of • model the historical and present-day slope, and directly through sediments hydraulic head trends along valley floors. • model possible future salinity mitigation scenarios for the aquifer. Site Description Within the Murray-Darling Basin, Kyeamba Creek is a third-order catchment feeding the Murrumbidgee River. The catchment is located south-east of the city of Wagga Wagga in central New South Wales. The major surface drainage features are Kyeamba, Livingstone and O’Briens Creeks. Average annual rainfall is 650 mm, with a gradient decreasing from south to north from the granite highlands to the alluvial plains at the confluence with the Murrumbidgee. Land Location of ‘Intermediate and Local Flow Systems in use is dominantly cattle grazing, with fractured rock aquifers’ in the Murray-Darling Basin. subordinate cropping, horticulture and, in the higher country, sheep grazing. In the Kyeamba catchment, salinity is manifest as small, scattered patches of Groundwater Flow System salinised land and locally shallow, saline The catchment, covering an area of groundwater. Increasing stream salinity and approximately 600 km2, lies within an salt export to the Murrumbidgee River are intermediate-scale fractured rock aquifer. the main salinity issues in the area. These Overlying valley fill alluvium represents a salinisation outcomes are particularly shallow secondary, local-scale aquifer promoted in the lower landscape by a lack system. The catchment thus contains a of hydraulic gradient, as well as by dual aquifer system: upper local-scale restrictions in the aquifer caused by sub- alluvial aquifers and an intermediate-scale, surface highs, typically of granite. deeper fractured rock aquifer. ii CATCHMENT CHARACTERISATION, KYEAMBA CREEK CASE STUDY the outbreak of surface salinity Current estimations suggest that the is the overlying local alluvial system. The quantity of salt being exported from the system is highly responsive to revegetation / Kyeamba catchment is the second largest reafforestation management options. Further, per unit area in the Murrumbidgee region. sub-surface salt stores can be mobilised Notwithstanding, the total salt contribution upward by the hydraulic heads in the from Kyeamba of 20,000 t/yr constitutes fractured rock, and become available for only a maximum of five per cent of the delivery to the stream network from the salt load measured in the Murrumbidgee alluvial fill. River passing Wagga Wagga. Salt loads are highly variable, however, ranging from While broad-scale reafforestation may 200,000 to 700,000 tonnes per year alleviate salinity concerns in the long term, passing Wagga Wagga. the fact that groundwater levels are high and stable, i.e. in dynamic equilibrium, Groundwater modelling means that the system may continue as a viable agricultural region for the foreseeable The FLOWTUBE model, a simple future. groundwater model based on Darcy’s Law, Kyeamba Creek catchment may be typical was used to simulate the variation in of many within the Lachlan Fold Belt groundwater on the groundwater flow country of central New South Wales and system. The model resolves for changes in northern Victoria. Extension of findings to hydraulic head induced by recharge and other catchments is feasible, following discharge fluxes, and lateral transfers in the detailed evaluation of local hydrogeological direction of flow, and is represented