Preliminary Ecological Water Requirements of Collie River East Branch: Risk Assessment of Salinity Mitigation Diversion Scenarios prepared for by Wetland Research & Management October 2007 EWRS OF COLLIE RIVER EAST BRANCH – RISK ASSESSMENT OF DIVERSIONS Preliminary Ecological Water Requirements of Collie River East Branch: Risk Assessment of Salinity Mitigation Diversion Scenarios Report Prepared for: THE DEPARTMENT OF WATER Level 4, 168 St Georges Terrace Perth Western Australia 6000 PO Box K822 Perth Western Australia 6842 Ph (08) 6364-6822 By: Wetland Research & Management 28 William Street, Glen Forrest, WA 6071, Australia Ph (61 8) 9298 9807, Fax (61 8) 6488 1029, e-mail: [email protected] October 2007 Frontispiece (clockwise from top left): East Branch of the Collie at Coolangatta Gauging Station (photo: Katherine Bennett, December 2005), long-necked tortoise Chelodina oblonga (photo by Andrew Storey, January 2006), and Crinia insignifera taken form Bingham River (photo by Andrew Storey). __________ Wetland Research & Management __________ i EWRS OF COLLIE RIVER EAST BRANCH – RISK ASSESSMENT OF DIVERSIONS Study Team Management: Andrew W. Storey Field Work: Andrew W. Storey & Glenn Shiell Macroinvertebrate Identification: Lisa Chandler Hydraulic Modelling: Andrew Storey & Jess Lynas Report: Andrew Storey & Jess Lynas Recommended Reference Format WRM (2007) Preliminary Ecological Water Requirements of Collie River East Branch: Risk Assessment of Salinity Mitigation Diversion Scenarios. Unpublished report by Wetland Research and Management to Department of Water, Perth Western Australia. October 2007. Disclaimer This document was based on the best information available at the time of writing. While Wetlands Research and Management (WRM) has attempted to ensure that all information contained within this document is accurate, WRM does not warrant or assume any legal liability or responsibility to any third party for the accuracy, completeness, or usefulness of any information supplied. The views and opinions expressed within are those of WRM and do not necessarily represent Department of Water policy. No part of this publication may be reproduced in any form, stored in any retrieval system or transmitted by any means electronic, mechanical, photocopying, recording or otherwise without the prior written permission of the Department of Water and WRM. __________ Wetland Research & Management __________ ii EWRS OF COLLIE RIVER EAST BRANCH – RISK ASSESSMENT OF DIVERSIONS CONTENTS 1 INTRODUCTION ..........................................................................................................................................................1 1.1 BACKGROUND .......................................................................................................................................................1 1.2 DIVERSION PROPOSAL ..........................................................................................................................................2 1.3 REVIEW OF EXISTING EWRS ON THE COLLIE RIVER ............................................................................................2 1.3.1 Existing EWRs...............................................................................................................................................2 1.3.2 Hydraulic modelling ......................................................................................................................................4 1.3.3 Identification of values and processes.......................................................................................................4 1.3.4 Flow objectives..............................................................................................................................................5 1.3.5 Comparison of recommended flow regimes .............................................................................................8 1.4 STUDY OBJECTIVES ..............................................................................................................................................9 1.5 STATUTORY/LEGISLATIVE FRAMEWORK..............................................................................................................10 1.6 ECOLOGICAL WATER REQUIREMENTS (EWRS)..................................................................................................11 1.7 ENVIRONMENTAL WATER PROVISIONS (EWPS).................................................................................................12 2 FLOW EVENTS METHOD FOR DETERMINATION OF EWRS.........................................................................13 3 THE COLLIE RIVER CATCHMENT........................................................................................................................15 3.1 CLIMATE ..............................................................................................................................................................15 3.2 GEOMORPHOLOGY ..............................................................................................................................................15 3.3 HYDROGEOLOGY.................................................................................................................................................16 3.4 VEGETATION........................................................................................................................................................17 4 HYDROLOGICAL STATE OF THE CATCHMENT...............................................................................................18 4.1 AVAILABLE DATA .................................................................................................................................................18 4.2 RAINFALL.............................................................................................................................................................18 5 SALINITY ....................................................................................................................................................................20 6 HYDRAULIC MODELLING ......................................................................................................................................22 6.1 INTRODUCTION ....................................................................................................................................................22 6.2 METHODS............................................................................................................................................................22 6.2.1 Survey reaches ...........................................................................................................................................22 6.2.2 Cross-sectional surveys.............................................................................................................................22 6.2.3 HEC-RAS modelling...................................................................................................................................23 6.3 RESULTS .............................................................................................................................................................26 6.3.1 Reach characteristics.................................................................................................................................26 6.3.2 HEC-RAS models .......................................................................................................................................28 7 WATER-DEPENDENT ECOLOGICAL VALUES..................................................................................................32 7.1 METHODS............................................................................................................................................................32 7.1.1 Site locations ...............................................................................................................................................32 7.1.2 Physico-chemical parameters...................................................................................................................33 7.1.3 Macroinvertebrate fauna............................................................................................................................33 7.1.4 Fish fauna ....................................................................................................................................................33 7.1.5 Faunal EWRs ..............................................................................................................................................35 7.2 RESULTS & DISCUSSION .....................................................................................................................................35 7.2.1 Physico-chemical parameters...................................................................................................................35 7.2.1.1 Patterns in physico-chemical data .................................................................................................38 7.2.2 Macroinvertebrates.....................................................................................................................................39 7.2.2.1 Taxonomic composition...................................................................................................................39 7.2.2.2 Taxa richness....................................................................................................................................39