Study of Ecological Water Requirements on the Gnangara and Jandakot Mounds Under Section 46 of the Environmental Protection Act
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Study of EWRs on the Gnangara and Jandakot Mounds Under Section 46: Task 1 FINAL Sept. 2004 Study of Ecological Water Requirements on the Gnangara and Jandakot Mounds under Section 46 of the Environmental Protection Act Task 1: Identification and Re-evaluation of Ecological Values Prepared for: The Water and Rivers Commission Prepared by: Dr. R. Froend1, R. Loomes1, Dr. P. Horwitz1, R. Rogan1, Dr. P. Lavery1, J. How1, Dr. A. Storey2, M. Bamford3 and B. Metcalf3 1Centre for Ecosystem Management, ECU. 2School of Animal Biology, UWA 3MJ and AR Bamford, Consulting Ecologists. Centre for Ecosystem Management, ECU, Joondalup 1 Study of EWRs on the Gnangara and Jandakot Mounds Under Section 46: Task 1 FINAL Sept. 2004 TABLE OF CONTENTS BACKGROUND............................................................................................................................................3 1: IDENTIFICATION AND RE-EVALUATION OF ECOLOGICAL VALUES ..................................4 1A. IDENTIFICATION OF ECOLOGICAL VALUES .............................................................................................4 1a.1. Restatement of the 1995, 1997, 1991 and 1992 values and where applicable, re-assessment and redefinition of these values where they have changed. ..........................................................................4 Groundwater Dependent Ecosystems Identified in the ‘Review of Proposed Changes to Environmental Conditions – Gnangara Mound Groundwater Resources (Section 46)’ (WAWA, 1995)................................. 11 Wetlands .........................................................................................................................................................11 Terrestrial Phreatophytic Vegetation...............................................................................................................15 Cave Streams and Pools.................................................................................................................................17 East Gnangara Environmental Water Provisions Plan (WRC, 1997)............................................................. 19 Wetlands and Mound Springs .........................................................................................................................19 Terrestrial Phreatophytic Vegetation...............................................................................................................21 Jandakot Groundwater Scheme Stage 2 PER (WAWA, 1991) & Environmental Management Programme – Jandakot Groundwater Scheme Stage 2 (WAWA, 1992)................................................................................. 21 Wetlands .........................................................................................................................................................22 Terrestrial phreatophytic vegetation................................................................................................................24 1a.2. Identification of the ecological values of GDEs in the wider study area that were not considered in 1995, 1997 and 1991/92 but are now appropriate to define............................................................86 1B. CONSIDERATION OF HOW ECOLOGICAL VALUES MAY CHANGE UNDER A DRY CLIMATE SCENARIO OR OTHER LAND-USE CHANGES.....................................................................................................................135 1C. PROPOSE MANAGEMENT OBJECTIVES FOR THE VALUES IDENTIFIED IN TASKS 1A. AND 1B.................155 REFERENCES ..........................................................................................................................................172 APPENDICES ...........................................................................................................................................178 APPENDIX 1: LISTING OF YANCHEP CAVES OF THE YEAL STUDY AREA (SUPPLIED BY LEX BASTIAN) .....178 Centre for Ecosystem Management, ECU, Joondalup 2 Study of EWRs on the Gnangara and Jandakot Mounds Under Section 46: Task 1 FINAL Sept. 2004 BACKGROUND (Excerpts of the WRC Project Brief (RFT No. 0001/2003) are included below as background for this first stage of the project) The Water and Rivers Commission manages groundwater resources of the Gnangara and Jandakot Mounds primarily though control of abstraction that might affect environmental values associated with groundwater dependent ecosystems over critical areas of the Mounds. As a condition of environmental approvals for abstraction, the Water and Rivers Commission is required to report annually to the Environmental Protection Authority on the performance if the Mounds and effects on associated environmental values. Detailed reports are required on a triennial basis. Over recent years, a number of environmental conditions for the Mounds have been transgressed, despite significant efforts to reduce public abstraction in sensitive areas. However, preliminary investigations indicate that in many cases the environmental values identified as the protection objective of these conditions may not have been materially affected. The Water and Rivers Commission is undertaking a review of the environmental conditions of approval for the management of the groundwater resources of the under Section 46 of the Environmental Protection Act 1986. The Environmental Protection Authority has endorsed a two-stage approach. Stage 1 comprised an initial investigation into critical areas where breaches of environmental conditions have occurred and a proposal for a short-term management strategy for the summers of 2001/02 and 2002/03. Stage II is to involve a rigorous investigation and review of environmental criteria, climate variability, long-term groundwater level behaviour, management of public and private abstraction and pine management plus offsetting factors such as urbanisation (including water sensitive urban design) and the Gnangara Park options. This is expected to provide the basis for a comprehensively revised management program for the relevant groundwater resources with respect to their groundwater dependent ecosystems, abstraction, pine clearing and Gnangara Park revegetation. This ecological water requirements study is one of several specific studies being undertaken as input into the Stage II review. This study is aimed at reviewing the groundwater dependent ecosystem values in the study area to be protected through water and land planning and management decision making. Within this, there are three detailed aspects to be considered: 1. ecological water requirements and environmental water provisions; 2. environmental criteria and the form of future environmental conditions; and 3. biological monitoring techniques and programs. Centre for Ecosystem Management, ECU, Joondalup 3 Study of EWRs on the Gnangara and Jandakot Mounds Under Section 46: Task 1 FINAL Sept. 2004 1: IDENTIFICATION AND RE-EVALUATION OF ECOLOGICAL VALUES 1a. Identification of ecological values Desktop review of ecological values identified in the 1995 Section 46 Review (Gnangara), 1997 East Gnangara Environmental Water Provisions Plan, and 1991 Public Environmental Review and 1992 Environmental Management Programme (Jandakot). 1a.1. Restatement of the 1995, 1997, 1991 and 1992 values and where applicable, re-assessment and redefinition of these values where they have changed. In this section of the report the relevant documents and associated literature are considered in a review of ecological values. All Previous GDE values are restated as published and presented in tabular form along with previous values of wetlands, mound springs, caves and terrestrial vegetation identified by other sources. River base-flow and near-shore marine systems were not considered in previous reports and will therefore be discussed in the following section (1a.2). Due to the extent of remnant terrestrial vegetation in north Gnangara and large number of wetlands within both the Jandakot and Gnangara study areas, wetlands and terrestrial vegetation are divided into sub-groups based on vegetation complexes described by Heddle et al. (1980), for ease of description. Changes in ecological condition, as noted during monitoring, are also presented in tabular form. This information is used to justify restatement, reassessment and/or redefinition of ecological values by Core Technical Group members. The majority of the work associated with this task is desk-based and draws from the field experience of the project team and their extensive quantitative databases on GDE parameters within the study area. Wetland Ecosystems (including Mound Springs) The following are recognized as generic wetland values; o Aesthetics and recreation o Filter surface water run-off o Flood mediation o Provide complex habitat o Biota adapted to and rely on water above or near surface – Support vegetation types less tolerant to water level declines – Littoral zone and associated habitats important for invertebrates which form basis of food-chain for other fauna – Amphibians require clear water in lakes – Waterbirds, tortoise and mammals depend on wetland vegetation and water itself Centre for Ecosystem Management, ECU, Joondalup 4 Study of EWRs on the Gnangara and Jandakot Mounds Under Section 46: Task 1 FINAL Sept. 2004 A substantial volume of work has been undertaken on wetlands of the Swan Coastal Plain. This work represents a valuable source of information on ecological values of dependent ecosystems in the study areas. A two-tiered approach to assessing wetland values was applied