Aquatic Ecology and Waterbirds at Lake Disappointment: Additional Studies Prepared for: Reward Minerals Limited July 2017 Final Report Lake Disappointment Aquatic Ecology Reward Minerals Ltd Aquatic Ecology and Waterbirds at Lake Disappointment: Additional Studies Bennelongia Pty Ltd 5 Bishop Street Jolimont WA 6014 P: (08) 9285 8722 F: (08) 9285 8811 E: [email protected] ABN: 55 124 110 167 Report Number: 301 Report Version Prepared by Reviewed by Submitted to Client Method Date Anton Mittra Draft Stuart Halse email 12 July 2017 Michael Curran Anton Mittra Final Stuart Halse email 20 July 2017 Michael Curran BEC_Disappointment aquatic ecology_FINAL_20vii17.docx This document has been prepared to the requirements of the Client and is for the use by the Client, its agents, and Bennelongia Environmental Consultants. Copyright and any other Intellectual Property associated with the document belongs to Bennelongia Environmental Consultants and may not be reproduced without written permission of the Client or Bennelongia. No liability or responsibility is accepted in respect of any use by a third party or for purposes other than for which the document was commissioned. Bennelongia has not attempted to verify the accuracy and completeness of information supplied by the Client. © Copyright 2017 Bennelongia Pty Ltd. i Lake Disappointment Aquatic Ecology Reward Minerals Ltd EXECUTIVE SUMMARY Reward Minerals Limited (Reward) is currently examining the feasibility of mining potash from Lake Disappointment, 138 km south of Telfer and 285 km east of Newman in the northern Little Sandy Desert IBRA bioregion. Impact areas on the main lake (ponds and dumps, brine trenches) equate to 7,210 ha (approximately 5.2% of the total lake surface) and expected life of mine is 20 years. Brine in the lakebed will be extracted and concentrated using trenches and/or production bores in the northern and western parts of the Lake and on the adjacent shoreline and dune systems. A characterisation of ecological values of Lake Disappointment was undertaken by Bennelongia via field survey in March 2017, building on previous survey in January–February 2016. Specific objectives were to characterise aquatic invertebrate assemblages, diatom assemblages and post-flood use of the lake by waterbirds. Survey in 2017 occurred after a major flooding event. Survey comprised sampling for aquatic invertebrates (250 µm and 50 µm sweep netting), diatoms and macrophytes at 18 sites in and around Lake Disappointment, including less-saline claypans around the hypersaline main playa. A comprehensive waterbird survey of the main playa and some surrounding claypans was undertaken by helicopter. A total of 109,812 waterbirds of 28 species were counted at Lake Disappointment. Ninety-five percent of the birds occurred on the main saline playa, with the overall assemblage dominated by Banded Stilt (93% of all birds). The next-most common species were Grey Teal, Red-necked Avocet, Black-winged Stilt, Whiskered Tern and Gull-billed Tern. Ten species showed evidence of current or recent breeding, with six species breeding on the main saline playa (Grey Teal, Banded Stilt, Red-necked Avocet, Red-capped Plover, Gull-billed Tern, Little Egret) and seven species breeding in fresh or less-saline claypans (Hardhead, Grey Teal, Hoary-headed Grebe, Eurasian Coot, Black-winged Stilt, Red-necked Avocet and Gull-billed Tern). Lake Disappointment appears to be a significant breeding site for Banded Stilts at the national level. This species accounted for 99% of current nesting activity and nearly 94% of all young birds. Current and recent breeding by this species was observed at 10 islands (five of which contained very large nesting colonies of 2,000–27,000 nests per island). Islands are critical for successful breeding by Banded Stilt and all breeding by this species was on natural islands. Three other species with a substantial amount of observed breeding activity were Red-necked Avocet, Gull-billed Tern and Grey Teal. Red-necked Avocets were seen breeding in small numbers on small man-made islands. Including previous results, at least 193 species of aquatic invertebrate have been recorded in and around Lake Disappointment, with the vast majority of species recorded at surrounding claypans that are less saline than the main playa. Groups that were notably rich were rotifers, cladocerans, conchostracans, ostracods and insects. Eighteen species of crustacean are currently known only from claypans surrounding Lake Disappointment and some of these may be range-restricted. None of these species occurred in the main playa. Richness in the Lake Disappointment system as a whole (including surrounding pans) is high relative to most arid zone wetland systems, although the main playa itself contains a depauperate assemblage of widespread species (mainly crustaceans). Sixty-nine diatom species were recorded in and around Lake Disappointment, including 35 species in the main playa, which is a rich community compared with that found in many inland salt lake systems. The main ecological value of the diatom community at Lake Disappointment is primary production, which in turn supports invertebrate and waterbird communities. ii Lake Disappointment Aquatic Ecology Reward Minerals Ltd CONTENTS Executive Summary ..................................................................................................................ii 1. Introduction .......................................................................................................................... 1 2. Background .......................................................................................................................... 1 2.1. Landscape ...................................................................................................................... 1 2.2. Historic Rainfall and Flooding ....................................................................................... 4 2.2.1. Rainfall Prior to 2017 Survey .................................................................................... 4 2.3. Biological Context ......................................................................................................... 4 2.3.1. Aquatic Invertebrates ............................................................................................. 4 2.3.2. Diatoms ...................................................................................................................... 4 2.3.3. Macrophytes............................................................................................................. 5 2.3.4. Waterbirds ................................................................................................................. 5 3. Survey Methods .................................................................................................................... 5 3.1. Sampling Effort ............................................................................................................... 5 3.2. Sampling Methods ......................................................................................................... 7 3.2.1. Waterbirds ................................................................................................................. 7 3.2.2. Aquatic Invertebrates ............................................................................................. 7 3.2.3. Diatoms ...................................................................................................................... 7 3.2.4. Macrophyte .............................................................................................................. 7 3.3. Habitat Characterisation .............................................................................................. 7 4. Results .................................................................................................................................... 7 4.1. Waterbirds ....................................................................................................................... 7 4.2. Aquatic Invertebrates ................................................................................................... 8 4.2.1. Distributions and Patterns of Species Occurrence ............................................ 15 4.3. Diatoms ......................................................................................................................... 18 4.3.1. Distributions and Patterns of Species Occurrence ............................................ 18 4.4. Macrophyte .................................................................................................................. 19 5. Ecological and Conservation Values ............................................................................. 19 6. Conclusions ......................................................................................................................... 20 7. References .......................................................................................................................... 21 8. Appendices ........................................................................................................................ 23 Appendix 1. Sampling Effort, water chemistry and descriptions of sites sampled in March 2017. ............................................................................................................................ 23 Appendix 2. Site photographs. ............................................................................................ 24 Appendix