DEPTHS AND SALINITIES OF WETLANDS IN SOUTH-WESTERN AUSTRALIA: 1977 - 2000 J.A.K. Lane, G.B. Pearson, A.G. Clarke, Y.C. Winchcombe December 2004 and D.R. Munro (dec.) Cover Main picture Chandala Swamp in Nov 2004. Photo - Grant Pearson Insets (L-R) Don Munro sampling Poorginup Swamp in 1981. Photo - Cliff Young Allan Gregory surveying a gauge at Wheatfield Lake in April 2003. Photo - Alan Clarke Grant Pearson and Paul Nas surveying Dumbleyung Lake in June 1998. Photo - Jim Lane Alan Clarke sampling Mortijinup Lake in Nov 2003. Photo - Yvonne Winchcombe Cover Design Wendy Paine (Planet Graphics, Busselton) © Copyright 2004 Department of Conservation & Land Management. All rights reserved. CONTENTS SUMMARY.............................................................................................................................. 1 1. INTRODUCTION .......................................................................................................... 4 2. BACKGROUND............................................................................................................. 4 3. THE WETLANDS.......................................................................................................... 6 4. METHODS...................................................................................................................... 8 4.1 Water levels ............................................................................................................. 8 4.2 Salinities................................................................................................................... 9 4.3 Sampling periods...................................................................................................... 9 4.4 Data management................................................................................................... 10 4.5 Data verification..................................................................................................... 10 4.6 Descriptive statistics .............................................................................................. 11 4.7 Trends analysis....................................................................................................... 11 5. RESULTS AND DISCUSSION................................................................................... 12 5.1 Descriptive statistics (means, minima, maxima, percentiles, variability, etc) ....... 12 5.2 Trends in depths and salinities over 20 or more years ........................................... 32 5.3 Patterns of depth and salinity variation.................................................................. 33 5.4 Relationships between depth and salinity trends ................................................... 40 5.5 Significant long-term trends in depths and salinities ............................................. 40 6. GENERAL ISSUES...................................................................................................... 51 6.1. Start and end years and the influence of rainfall.................................................... 51 6.2 Potential for hidden trends ..................................................................................... 51 6.3 Protocol for early detection of change ................................................................... 51 6.4 Period required to determine ‘normal’ hydrological regimes ................................ 52 6.5 A search for pre-SWWMP data ............................................................................. 52 6.6 Land clearing and wetland hydrology.................................................................... 53 7. USES, RELATIONSHIPS, REPORTING AND SUPPLY OF SWWMP DATA... 53 7.1 Uses of SWWMP data ........................................................................................... 53 7.2 SWWMP and other salinity programs of CALM .................................................. 53 7.3 Future reporting...................................................................................................... 54 7.4 Data supply ............................................................................................................ 54 8. ACKNOWLEDGEMENTS ......................................................................................... 55 9. REFERENCES ............................................................................................................. 55 Depths and Salinities of Wetlands in South-Western Australia: 1977-2000 i TABLES 1. Trends in depths and salinities of 41 wetlands monitored for ≥20 years…………………………………. 41 FIGURES 1. Wetlands currently monitored under Salinity Strategy and wetlands previously monitored………………. 7 2. September depths (medians, minima, maxima, variability)……………………………………………..… 16 3. November depths (medians, minima, maxima, variability)………………………………………….……. 20 4. September salinities (medians, minima, maxima, variability)…………………………………………….. 24 5. November salinities (medians, minima, maxima, variability)…………………………………………..… 28 6. Depth trends and significance (Sep, Nov, Sep+Nov)……………………………………………………… 34 7. Salinity trends and significance (Sep, Nov, Sep+Nov)……………………………………………………. 37 8. Bambun rainfall, depth and salinity trends…………………………………………..…………………….. 61 9. Beverley…………………………………………………………………………………………………… 62 10. Boyup Brook 18239……………………………………………………………………….………………. 63 11. Bryde………………………………………………………………………………………….…………… 64 12. Byenup…………………………………………………………………………………………….………. 65 13. Casuarina…………………………………………………………………………………………….…….. 66 14. Chandala…………………………………………………………………………………………………… 67 15. Coyrecup………………………………………………………………………………………………….... 68 16. Crackers……………………………………………………………………………………………………. 69 17. Dobaderry……………………………………………………………….…………………………………. 70 18. Dulbinning…………………………………………………………………….…………………………….71 19. Dumbleyung……………………………………………………………………………………………….. 72 20. Eganu………………………………………………………………………………………………………. 73 21. Forrestdale…………………………………………………………………………………………………. 74 22. Gore…………………………………………………………………………………………………………75 23. Harvey 12632…………………………………………………………………………………………..…. 76 24. Jandabup…………………………………………………………………………………………………… 77 25. Jerdacuttup………………………………………………………………………………………………… 78 26. Joondalup…………………..………………………………………………………………………………..79 27. Kwornicup……………………..………………………………………………………………………….. 80 28. Logue………………………………..…………………………………………………………………….. 81 29. Moates………………………………….…..……………………………………………………………… 82 30. Muir……………………………………………..………………………………………………………… 83 31. Nine Mile…………………………………………..……………………………………………………… 84 32. Pleasant View…………………………………………..…………………………………………………. 85 33. Poorginup……………………………………………………..…………………………………………… 86 34. Powell……………………………………………………………..………………………………………. 87 35. Shark……………………………………………………………………………………………………….. 88 36. Station……………………………………………………………………………………………………… 89 37. Taarblin……………………………………………………………………………..…………………….. 90 38. Thomsons……………………………………………………………………………..…………………… 91 39. Toolibin…………………………………………………………………………………………………… 92 40. Tordit-Gurrup…………………………………………………………………………………..…………. 93 41. Towerrinning……………………………………………………………………………………………… 94 42. Unicup…………………………………………………………………………………………………….. 95 43. Walbyring…………………………………………………….…………………………………………… 96 44. Wannamal………………………………………………………….……………………………………… 97 45. Warden………………………………………………………………….………………………………… 98 46. Warrinup…………………………………………………………………..………………………………. 99 47. Yarnup………………………………………………………………………….………………………… 100 48. Yealering…………………………………………………………………………….…………………… 101 APPENDICES 1. Monitored wetlands’ names, codes, coordinates, LGAs, monitoring periods and status………………… 102 2. September depths (years monitored, years dry, means, percentiles, ranges, variability, trends)………… 106 3. November depths (years monitored, years dry, means, percentiles, ranges, variability, trends)………… 110 4. September salinities (years monitored, years dry, means, percentiles, ranges, variability, trends)……… 114 5. November salinities (years monitored, years dry, means, percentiles, ranges, variability, trends)………. 120 6. Distances, directions and rainfalls of Meteorological Stns. closest to wetlands monitored ≥20 years….. 124 7. Numbers of wetlands with 1, 2, 3, 4, …, etc. years of depth and salinity records……………………..… 127 8. Reports and publications in which significant use is made of SWWMP data…………………………… 128 ii Depths and Salinities of Wetlands in South-Western Australia: 1977-2000 SUMMARY This report presents 1977-2000 water depth and salinity data from the South-West Wetland Monitoring Program (SWWMP) conducted by the Western Australian Department of Conservation and Land Management (CALM). Summaries of September and November depth and salinity data from 151 SWWMP wetlands across south-western Australia are presented, together with long-term trends in these parameters at 41 wetlands monitored for 20 or more years. Most of these wetlands are within conservation reserves vested in the Conservation Commission of Western Australia and managed by CALM. Several are on private property. SWWMP began in 1977 with a decision in the former Department of Fisheries and Wildlife to commence a program of September and November water level monitoring on a large sample of south- west wetlands in order to provide an objective basis for determining annual waterfowl hunting season specifications. Salinity was also to be monitored because of its potential impact on waterfowl and their habitats. Eighty-two wetlands were monitored between 1977 and 1980. In 1981 the program was expanded to coincide with a four-year assessment of waterbird use of south-west Wetland Nature Reserves