ECOLOGICAL CHARACTER DESCRIPTION OF THE LAKE WARDEN SYSTEM RAMSAR SITE, ESPERANCE, WESTERN AUSTRALIA A report by the Department of Environment and Conservation Ecological Character Description of the Lake Warden System Ramsar Site Acknowledgements Funding for the development of this document was sourced jointly from the Natural Heritage Trust (NHT) and the State and Commonwealth contributions to the National Action Plan for Salinity and Water Quality (NAP). NHT and NAP are jointly administered by the Australian Government departments of Agriculture, Fisheries and Forestry and the Environment, Water, Heritage and the Arts and the WA Natural Resource Management Office. In-kind contributions were gratefully received from the organisations represented on the Technical Advisory Group. Document Preparation This document has been prepared by the Wetlands Section of the Department of Environment and Conservation. Gareth Watkins - Author / conceptual models and graphics Jennifer Higbid - Internal review Technical Advisory Group Members Robyn Cail South Coast NRM David Cale DEC Sarah Comer DEC Ian Hartley Esperance Regional Forum Jennifer Higbid DEC Tegan Laslett DEC John Lizamore DEC Ken Read Esperance Bird Observers Group John Simons DAFWA Thank you to the following people for their contributions Nikki Cowcher DEC Henry Dabb South Coast NRM Greg Freebury DEC Paul Galloway DAFWA Photo credits Cover photograph: Mullet Lake, Esperance (J. Higbid) Internal photographs: G. Daniel, J. Higbid _________________________________________________________________________ I Ecological Character Description of the Lake Warden System Ramsar Site Other credits Symbols in conceptual models courtesy of the Integration and Application Network <http://ian.umces.edu/symbols/>, University of Maryland Center for Environmental Science To reference this document Department of Environment and Conservation (2009). Ecological Character Description of the Lake Warden System Ramsar Site: A Report by the Department of Environment and Conservation. Prepared by G. Watkins, Department of Environment and Conservation, Perth, Western Australia. Introductory Notes This Ecological Character Description (ECD Publication) has been prepared in accordance with the National Framework and Guidance for Describing the Ecological Character of Australia’s Ramsar Wetlands (National Framework) (Department of the Environment, Water, Heritage and the Arts, 2008). The Environment Protection and Biodiversity Conservation Act 1999 (EPBC Act) prohibits actions that are likely to have a significant impact on the ecological character of a Ramsar wetland unless the Commonwealth Environment Minister has approved the taking of the action, or some other provision in the EPBC Act allows the action to be taken. The information in this ECD Publication does not indicate any commitment to a particular course of action, policy position or decision. Further, it does not provide assessment of any particular action within the meaning of the Environment Protection and Biodiversity Conservation Act 1999 (Cth), nor replace the role of the Minister or his delegate in making an informed decision to approve an action. This ECD Publication is provided without prejudice to any final decision by the Administrative Authority for Ramsar in Australia on change in ecological character in accordance with the requirements of Article 3.2 of the Ramsar Convention. Disclaimer While reasonable efforts have been made to ensure the contents of this ECD are correct, the Commonwealth of Australia as represented by the Department of Sustainability, Environment, Water, Population and Communities does not guarantee and accepts no legal liability whatsoever arising from or connected to the currency, accuracy, completeness, reliability or suitability of the information in this ECD. Note: There may be differences in the type of information contained in this ECD publication, to those of other Ramsar wetlands. _________________________________________________________________________ II Ecological Character Description of the Lake Warden System Ramsar Site TABLE OF CONTENTS GLOSSARY ......................................................................................................... VIII ABBREVIATIONS ................................................................................................. XII EXECUTIVE SUMMARY...................................................................................... XIII 1.0 INTRODUCTION ............................................................................................... 1 1.1 SITE DETAILS ......................................................................................................... 2 1.2 PURPOSE OF AN ECOLOGICAL CHARACTER DESCRIPTION .......................... 3 1.2.1 OBJECTIVES OF THE LAKE WARDEN SYSTEM RAMSAR SITE ECOLOGICAL CHARACTER DESCRIPTION ................................................................................................... 5 1.3 RELEVANT TREATIES, LEGISLATION AND REGULATIONS .............................. 6 1.3.1 INTERNATIONAL AGREEMENTS/CONVENTIONS ....................................................... 6 1.3.2 NATIONAL LEGISLATION ............................................................................................... 7 1.3.3 WESTERN AUSTRALIA STATE LEGISLATION ............................................................. 8 2.0 DESCRIPTION OF THE LAKE WARDEN SYSTEM RAMSAR SITE ............. 10 2.1 BACKGROUND ..................................................................................................... 10 2.2 LAND TENURE AND LAND USE .......................................................................... 11 2.4 CLIMATE ............................................................................................................... 13 2.5 WETLAND TYPES ................................................................................................ 16 2.6 RAMSAR CRITERIA ............................................................................................. 18 2.6.1 RAMSAR CRITERIA UNDER WHICH THE SITE WAS DESIGNATED ........................ 18 2.6.2 CURRENT RAMSAR CRITERIA .................................................................................... 20 2.6.2.1 ASSESSMENT AGAINST EACH OF THE RAMSAR CRITERIA FOR THE LAKE WARDEN SYSTEM RAMSAR SITE ......................................................................................................................... 23 3.0 LAKE WARDEN SYSTEM RAMSAR SITE: CRITICAL ECOSYSTEM COMPONENTS, PROCESSES, BENEFITS AND SERVICES ............................. 27 3.1 CRITICAL ECOSYSTEM COMPONENTS AND PROCESSES ............................. 27 3.1.1 GEOMORPHOLOGY ...................................................................................................... 31 3.1.2 HYDROLOGY .................................................................................................................. 32 3.1.2.1 HYDROLOGICAL SETTING ............................................................................................ 33 3.1.2.2 SURFACE AND GROUND WATER INTERACTIONS............................................................. 35 3.2.2.3 HYDROLOGICAL REGIME OF THE MAJOR LAKES WITHIN THE RAMSAR SITE ..................... 39 3.2.2.4 CATCHMENT TRENDS .................................................................................................. 44 3.1.3 WATER QUALITY ........................................................................................................... 46 3.1.3.1 PHYSICO-CHEMICAL PROPERTIES OF THE MAJOR LAKES WITHIN THE RAMSAR SITE ........ 46 3.1.3.1.1 Salinity concentrations..................................................................................................46 3.1.3.1.2 pH ....................................................................................................................................51 3.1.3.1.3 Nutrient concentrations.................................................................................................52 3.1.3.2 CATCHMENT SURFACE AND GROUNDWATER PHYSICO-CHEMICAL PROPERTIES ............... 60 3.1.3.2.1 Salinity concentrations..................................................................................................60 3.1.3.2.2 pH ....................................................................................................................................60 3.1.3.2.3 Nutrient concentrations.................................................................................................61 3.1.4 PHYSICAL PROCESSES ............................................................................................... 62 3.1.5 WETLAND SOILS ........................................................................................................... 62 3.1.6 BIOTA .............................................................................................................................. 66 _________________________________________________________________________ I Ecological Character Description of the Lake Warden System Ramsar Site 3.1.6.1 WATERBIRDS ............................................................................................................. 66 3.1.6.1.1 Species diversity and abundance ................................................................................68 3.1.6.2 FISH ........................................................................................................................... 80 3.1.6.3 AQUATIC INVERTEBRATES ..........................................................................................