\,i AWESVILLE CHANNEL '1 I\ I MONI TOR IN G PROGRAMME !i I d- ~ :r TECHNICAL REVIEW },,. •u \· ij l '.( REPORT ;- :l I 11 ' 1 I lj / Submitted to ,,I THE WATER AND RIVERS COMMISSION ·, Prepmd by 1I f D.A. LORD & ASSOCIATES PTY. LTD . Plate 1: Macroalgal accumulations' at Coodanup, Peel Inlet Plate 2: Macroalgal harvesting in Peel Inlet. ~awesville Channel MONITORING PROGRAMME TECHNICAL REVIEW Prepared for: WATER AND RIVERS COMMISSION Prepared by: D.A. LORD & ASSOCIATES PTY LTD In conjunction with: ENVIRONMENTAL ADVISORY SERVICES WATER AND RIVERS COMMISSION WATER AND RIVERS COMMISSION REPORT WRT 28 1998 Acknowledgements This report was commissioned by the Water and Rivers Commission in conjunction with the Department of Transport. The contribution of the following agencies and organisations are gratefully acknowledged: Agriculture Western Australia Health Department of Western Australia Department of Conservation and Land Management Fisheries Western Australia Department of Environmental Protection The University of Western Australia Murdoch University Kinhill Pty Ltd ISBN 0-7309-7439-1 ISSN 1327-8436 Text printed on recycled stock December 1998 Contents EXECUTIVE SUMMARY .................................................................................................... v INTRODUCTION ...................................................................................................................... I 1.1 ENVIRONMENTAL SETTING ................................................................................................ ] I. I. I Location, climate and geomorphology ............................................................................ .1 1.1.2 Catchment land use .......................................................................................................... 2 1.1.3 The Peel-Harvey Estuarine System ................................................................................... 2 1.1.4 The algal problem ............................................................................................................. 2 1.2 SCOPE OF THE TECHNICAL REVIEW ................................................................................ 3 1.3 STUDY APPROACH ............................................................................................................... 3 1.4 DOCUMENT STRUCTURE ................................................................................................... 8 2. HYDRODYNAMICS ........................................................................................................... 9 2.1 TIDAL LEVELS ........................................................................................................................ 9 2.1.1 Prior to the opening of the Dawesville Channel .............................................................. 9 2.1.2 Predicted effects of the Dawesville Channel .................................................................... 9 2.1.3 Observed effects of the Dawesville Channel .................................................................... 9 2.2 WATER CIRCULATION AND STRUCTURE ......................................................................... 9 2.2.1 Prior to the opening of the Dawesville Channel .............................................................. 9 2.2.2 Predicted effects of the Dawesville Channel .................................................................. IO 2.2.3 Observed effects of the Dawesville Channel .................................................................. IO 2.3 EXCHANGE CHARACTERISTICS ...................................................................................... 10 2.3.1 Prior to the opening of the Dawesville Channel ........................................................... .10 2.3. 2 Predicted effects of the Dawesville Channel .................................................................. IO 2.3.3 Observed effects of the Dawesville Channel ................................................................. .10 2.4 EXTREME WATER LEVELS ................................................................................................ 11 2.4.1 Prior to the opening of the Dawesville Channel ........................................................... .1 l 2.4.2 Predicted effects of the Dawesville Channel .................................................................. 11 2.4.3 Observed effects of the Dawesville Channel .................................................................. 11 3. SEDIMENTS ......................................................................................................................... 12 3.1 ESTUARINE SEDIMENTS .................................................................................................... 12 3.1.1 Prior to the opening of the Dawesville Channel ............................................................ 12 3.1.2 Predicted effects of the Dawesville Channel .................................................................. 12 3.1.3 Observed effects of the Dawesville Channel .................................................................. 13 3.2 RIVERINE SEDIMENTS ....................................................................................................... 13 3.2. l Prior to the opening of the Dawesville Channel ............................................................ 13 3.2.2 Predicted effects of the Dawesville Channel .................................................................. 13 3.2.3 Observed effects of the Dawesville Channel .................................................................. 13 4. NEARSHORE MARINE AREAS ................................................................................ 14 4.1 SHORELINE AND CHANNEL STABILITY ........................................................................ 14 4.1.1 Prior to the opening of the Dawesville Channel ............................................................ 14 4.1.2 Predicted effects of the Dawesville Channel .................................................................. 14 4.1.3 Observed effects of the Dawesville Channel .................................................................. 14 4.2 NEARSHORE WATER QUALITY ........................................................................................ 14 4.2.1 Prior to the opening of the Dawesvil/e Channel ............................................................ 14 4.2.2 Predicted effects of the Dawesville Channel .................................................................. 15 4.2.3 Observed effects of the Dawesville Channel .................................................................. 15 4.3 NEARSHORE BENTHIC HABITATS ................................................................................... 15 4.3. 1 Prior to the opening of the Dawesville Channel ............................................................ 15 4.3.2 Predicted effects of the Dawesville Channel .................................................................. 15 4.3.3 Observed effects of the Dawesvi!le Channel .................................................................. 16 5. WATER QUALITY ............................................................................................................ 17 5.1 CATCHMENT NUTRIENT INPUTS .................................................................................... 17 5.1.l Catchment nutrient data pre-1989 .................................................................................. 17 5.1.2 Catchment nutrient data post 1989 ................................................................................. l 7 5.2 GROUNDWATER ................................................................................................................... 20 5.2.1 Prior to the opening of the Dawesville Channel ............................................................ 20 5.2.2 Predicted effects of the Dawesville Channel .................................................................. 20 5.2.3 Observed effects of the Dawesville Channel .................................................................. 20 5.3 ESTUARINE WATER QUALITY .......................................................................................... 20 5.3.1 Prior to the opening of the Dawesville Channel ............................................................20 5.3.2 Predicted effects of the Dawesville Channel .................................................................. 20 5.3.3 Observed effects of the Dawesville Channel .................................................................. 21 5.4 RIVERINE WATER QUALITY .............................................................................................. 22 5.4.1 Prior to the opening of the Dawesvil/e Channel ............................................................ 22 5.4.2 Predicted effects of the Dawesville Channel .................................................................. 22 5.4.3 Obsen1ed effects of the Dawesville Channel ................................................................. 22 6. ESTUARINE FLORA ...................................................................................................... 24 6.1 PHYTOPLANKTON ............................................................................................................... 24 6. l. 1 Prior to the opening of the Dawesville Channel ........................................................... 24 6.1.2 Predicted e_ffects of the Dawesville Channel ................................................................. 25 6.1.3 Observed effects