Bio-physical options to prevent, minimise or manage salinity issues in the Lockyer catchment Roger Shaw April 2008 Prepared for Lockyer Valley Regional Council Bio-physical options to prevent, minimise or manage salinity issues in the Lockyer catchment Roger Shaw April 2008 Prepared for Lockyer Valley Regional Council Copyright © April 2008. Roger Shaw and Lockyer Valley Regional Council. This work is copyright. It may be reproduced in part subject to the inclusion of full acknowledgement of the source of the material and no commercial use or sale of the information. Any other use requires the prior permission in writing from the copyright owners. Sources The source of some of the information in this report as acknowledged is from the Queensland Department of Natural Resources and Water under Licence agreement numbers USR: 2007/002223 and 2006/001702 to which the following applies: © The State of Queensland (Department of Natural Resources and Water) [2007]. In consideration of the State permitting use of this data it is acknowledged and agreed that the State gives no warranty in relation to the data (including accuracy, reliability, completeness, currency or suitability) and accepts no liability (including without limitation, liability in negligence) for any loss, damage or costs (including consequential damage) relating to any use of the data. Data must not be used for direct marketing or be used in breach of the privacy laws. Some of the copyright material has been modified by the author as stated in the text of the report. Disclaimer The views and conclusions contained in this document should not be interpreted as necessarily representing the official policies, either expressed or implied, of Gatton or Laidley Shire Councils, Lockyer Valley Regional Council, SEQ Catchments Ltd, their staff or the State of Queensland. The report covers a number of technical issues associated with the expression and management of salinity in the Lockyer Valley. It does not cover all the aspects concerned with salinity. The information and opinions in this report are not necessarily those of the copyright owners or the author. The information should not be acted on, or ignored, without independent consideration and advice. The author, editors, staff of Gatton Shire Council, Laidley Shire Council, Lockyer Valley Regional Council, SEQ Catchments Ltd and any organisations they may be associated with, and the organisations from which information has been obtained are not responsible for any loss or damage suffered by any person or corporation acting on, or refraining from acting upon, any material contained in this publication or an interpretation made on the basis of the content of this publication. The contents of this document have been compiled from a range of sources using a range of source materials and while reasonable care has been taken in its compilation, the organisations and individuals involved with the compilation of this document shall not be liable or responsible for any consequences which may result from any use of the contents of this document. The copyright owners make no representation, express or implied, with regard to the accuracy of the information contained in this report and cannot accept any legal responsibility or liability for errors or omissions that may be made. 2 Contents Executive summary and recommendations ........................................................................ iii List of Tables .....................................................................................................................xiiii List of Figures....................................................................................................................xiiii List of photographs...........................................................................................................xivv 1 Introduction.......................................................................................................................1 1.1 Objectives for this report...........................................................................................2 2 Salinity overview...............................................................................................................2 2.1 Concepts and definitions ..........................................................................................2 2.2 Salinity processes.....................................................................................................4 2.2.1 Watertable salinity ............................................................................................5 2.2.1.1 Mass balance of water and salt ...............................................................7 2.2.1.2 Forms of salinity.......................................................................................9 2.2.1.3 Equilibrium and resilience ......................................................................11 2.2.1.4 Stages of watertable salinity development and reclamation ..................13 2.2.2 Irrigation water salinity ....................................................................................17 2.2.2.1 Mass balance and leaching ...................................................................20 2.2.2.2 Soil stability ............................................................................................22 2.2.2.3 Soil salinity and sodicity equilibrium and resilience ...............................23 3 Watertable salinity in the Lockyer Valley........................................................................24 3.1 Distribution of watertable salinity ............................................................................24 3.2 Role of Winwill conglomerate .................................................................................25 3.3 Source of salts in the Lockyer Valley......................................................................31 3.4 Conceptual picture of salting processes in the Lockyer Valley...............................33 3.5 Salt mass balance of catchments...........................................................................36 3.6 Factors modifying the expression of watertable salinity .........................................38 3.7 Current and emerging pressures on watertable salinity .........................................43 4 Biophysical options to prevent, minimise or manage watertable salinity........................47 4.1 Do nothing ..............................................................................................................47 4.2 Stabilise ..................................................................................................................47 4.3 Reduce groundwater inputs (recharge area)..........................................................48 4.4 Intercept groundwater (transmission zone) ............................................................48 4.5 Increase groundwater outputs (discharge area).....................................................48 4.6 Store the salt ..........................................................................................................49 4.7 Remove the salt......................................................................................................50 4.8 Recycled water reuse .............................................................................................51 4.9 Management options and combinations that are unlikely to be effective for watertable salinity ...................................................................................................51 5 Irrigation water salinity in the Lockyer Valley..................................................................52 5.1 Salinity issues.........................................................................................................52 5.2 Soil stability.............................................................................................................55 5.3 Irrigation water salinity - equilibrium and feedbacks...............................................57 5.4 Current and emerging pressures in irrigation water................................................57 6 Management options for irrigation waters ......................................................................58 6.1 Method of irrigation.................................................................................................58 6.2 Timing of irrigation application................................................................................58 6.3 Quantity of irrigation application .............................................................................58 6.4 Mixing water supplies .............................................................................................58 7 Managing salinity in the Lockyer Valley..........................................................................59 7.1 Salinity risk assessment for the Lockyer Valley......................................................59 7.2 Ecological risk assessment process.......................................................................60 7.2.1 Scoping and formulating the salinity issue......................................................60 7.2.2 Identifying the sustainable outcomes perceived to be at risk .........................61 i 7.2.3 Identifying the pressures (hazards) likely to adversely impact upon sustainability outcomes...................................................................................63 7.2.4 Analysing the likelihood and consequences of the pressures on salinity .......64