Sampling and analysis of lakes in the Corangamite CMA region Report to the Corangamite Catchment Management Authority CCMA Project WLE/42-009: Client Report 3 Annette Barton, Andrew Herczeg, Jim Cox and Peter Dahlhaus CSIRO Land and Water Science Report 34/06 September 2006 Copyright and Disclaimer © 2006 CSIRO & Corangamite Catchment Management Authority. To the extent permitted by law, all rights are reserved and no part of this publication covered by copyright may be reproduced or copied in any form or by any means except with the written permission of CSIRO Land and Water or the Corangamite Catchment Management Authority. Important Disclaimer: CSIRO advises that the information contained in this publication comprises general statements based on scientific research. The reader is advised and needs to be aware that such information may be incomplete or unable to be used in any specific situation. No reliance or actions must therefore be made on that information without seeking prior expert professional, scientific and technical advice. To the extent permitted by law, CSIRO (including its employees and consultants) excludes all liability to any person for any consequences, including but not limited to all losses, damages, costs, expenses and any other compensation, arising directly or indirectly from using this publication (in part or in whole) and any information or material contained in it. From CSIRO Land and Water File: S:\CCMA\GDE_project\Photographs\SiteVisit23-25July2006, No1 Description: The dry crater which was Deep Lake. Photographer: Bob Smith, Ballarat of University © 2006 CSIRO ISSN: 1446-6171 Report Title Sampling and analysis of the lakes of the Corangamite CMA region Authors Dr Annette Barton 1, 2 Dr Andy Herczeg 1, 2 Dr Jim Cox 1, 2 Mr Peter Dahlhaus 3, 4 Affiliations/Misc 1. CSIRO Land and Water, PMB 2, Glen Osmond, SA, 5064 2. CRC for LEME, PO Box 1130, Bentley, WA, 6151 3. University of Ballarat, PO Box 663, Ballarat VIC, 3353 4. Dahlhaus Environmental Geology Pty Ltd, PO Box 318, Buninyong, VIC, 3357 CSIRO Land and Water Science Report 34/06 September 2006 Identification and review of the groundwater dependent ecosystems in the Corangamite CMA Page i Table of Contents 1. Introduction..................................................................................................................... 3 2. Lakes Inspection and Sampling.................................................................................... 3 3. Chemical Analyses......................................................................................................... 5 3.1. Field measurements.............................................................................................................. 5 3.2. Chemistry.............................................................................................................................. 5 3.3. Radon count.......................................................................................................................... 9 3.4. Stable isotopes ................................................................................................................... 10 4. Further Work................................................................................................................. 13 5. Acknowledgements...................................................................................................... 13 References ........................................................................................................................... 13 Identification and review of the groundwater dependent ecosystems in the Corangamite CMA Page ii 1. Introduction This is the third milestone report for the Corangamite Catchment Management Authority (CCMA) project WLE/42-009 – Understanding the processes causing salinity of the groundwater dependent ecosystems of the CCMA . The objectives of this third project report are to report on work undertaken during the third quarter-year phase, provide feed-back and chart future directions. Work to date has included the inspection and water sampling of 23 lakes in the CCMA region and chemical analyses of the water samples for radon, stable isotopes and major ions. 2. Lakes Inspection and Sampling Between 23-25 July a site visit was undertaken to sample as many lakes as possible in the CCMA region. Sampling was undertaken by Annette Barton, CSIRO, and Bob Smith, University of Ballarat. Table 1 gives a listing of the 46 lakes visited and a brief comment on the condition of these lakes. Specific sampling localities are shown in Figure 1. Approximately half of these lakes were dry or the water depth so small as to make it all but impossible to take a sample of water without disturbing and sampling lake sediments in the process. In a number of instances deep mud obstructed access, although for these cases it was thought that even if the water’s edge had been reached it would have been too shallow to sample. Figure 1. Lake sampling sites. Identification and review of the groundwater dependent ecosystems in the Corangamite CMA Page 3 Table 1. Listing of CCMA lakes Visited and Comment on Condition. Lake Name/Reference Condition Deep Lake Completely dry. No sample. Lake Logan Assumed dry. No sample. Lake Tooliorook Sample taken. Kooraweera Lakes (3) Water running into lake on Westbank Rd. Spring? Otherwise dry. Sample taken. Lake Milangil Virtually dry. Water too shallow to sample. Lake Round Dry. No sample. Lake Kariah Dry. No sample. Lake Colongulac Camperdown WWTP. Did not access due to signage from the South West Water Authority. Water visible. Lake Bullen Merri Sample taken. Lake Gnotuk Suds around rim. Sample taken. Lake Purrumbete Sample taken. Lake Koreetnung Dry (farmer’s advice). No sample. Lake Weeranganuk Dry. No sample. Lake Corangamite Dry in northern part. Very shallow in others and difficult to access due to mud. Only a small sample obtained. Lake Terangpom Shallow. Sample taken. Lake Coradgill Dry. Lakes Bulkil Narra, Punpundal & Tatutong assumed likewise. Lake Gnarpurt Dry. No sample. Lake Struan Sample taken. Lake Rosine Sample taken. Cundare Pool/Lake Martin Water running into inlet. Otherwise dry. Sample taken of inlet water. Weering Lake Sample taken. Upper Lough Calvert Shallow. Sample taken. Middle Lough Calvert Dry. No sample. Lower Lough Calvert Dry. No sample. Lake Cundare Sample taken. Thomas Lake Dry. No sample. Lake Beeac Water at surface. No sample. Lake Ondit Dry. No sample. Lake Purdiguluc Completely dry. Lakes Coragulac & Gnalinegurk assumed likewise. The Basins (2) Water in both lakes. Sample taken from West Basin. Lake Colac Sample taken. Lake Thurrumbong Dry. No sample. Lake Burn Very shallow. Could not access due to mud. No sample. Murdeduke Lake Sample taken. Gherang Lake Dry. No sample. Modewarre Lake Sample taken. Breamlea Wetlands Mostly dry. Sample taken from small pool. Reedy Lake Mostly dry. Sample taken from small pool. Connewarre Lake Much algae in water. Sample taken. Connewarre Swamp Sample taken. Barwon Estuary/Mouth Sample taken. Murtnagurt Swamp Mostly dry. No sample. Victoria Lake Sample taken. Identification and review of the groundwater dependent ecosystems in the Corangamite CMA Page 4 Sampling involved collecting a grab sample (most often using a bucket) and extracting a radon sample on site. Some chemical parameters were measured in the field including electrical conductivity (EC), pH, dissolved oxygen (DO) and temperature. Water and radon samples were freighted back to the CSIRO laboratory in Adelaide for analyses. Of particular interest was the sample collected from the Kooraweera Lakes at Westbank Road. Both the lake sampled, and others in the chain, appeared essentially dry however at this location a streamlet was discharging into one of the lakes and had formed a sizeable pond at its northern tip. Local knowledge suggests that the water emanates from Larra Spring which runs down from Mt Elephant to the north-west and feeds into the Kooraweera chain of lakes (pers. comm. D. Smithyman). This would indicate that the water sampled is groundwater and that these lakes typically have some groundwater dependence. 3. Chemical Analyses 3.1. Field measurements Field measurements for 23 of the 24 lakes sampled are given in Table 2. No field measurements were taken for Sample 6 (Lake Corangamite) as only a small amount of water was obtained due to the shallowness of the water body and the mud impediment. Electrical conductivity (EC) ranges from 134 mS/m for Kooraweera Lakes to 22 400 mS/m for Lake Weering. The higher EC values are likely to underestimate the salinity due to the non- linearity of EC to TDS relationship at high salinity. pH values tend to be in the alkaline range from 7.84 to 9.24 and these are reflected in high measured total alkalinity (Table 3). Most of the surface water had DO concentration less than 100% of that of atmospheric equilibrium indicating active biogeochemical oxidation occurring due to high organic matter concentrations. 3.2. Chemistry The dissolved solutes of the Corangamite Lakes are dominated by Na + and Cl - except for the most dilute lakes (Kooraweera Lakes and Lake Purrumbete) which have a slightly higher - + - proportion of HCO 3 as anions. In general, the dominance of Na and Cl over the other ions increases linearly as a function of TDS (Figure 2 and Figure 3). Most notably, Ca 2+ and - HCO 3 remain low throughout the entire salinity range indicating control of these dissolved ions through precipitation of carbonate minerals. The low salinity VVP groundwater