Benchmarking saline flows in key rivers and streams for resource condition target development SALINITY MONITORING IN THE MOORABOOL, BARWON, LAKE CORANGAMITE AND OTWAY BASINS Final 25 July 2005 Benchmarking saline flows in key rivers and streams for resource condition target development SALINITY MONITORING IN THE MOORABOOL, BARWON, LAKE CORANGAMITE AND OTWAY BASINS Final 25 July 2005 Sinclair Knight Merz ABN 37 001 024 095 590 Orrong Road, Armadale 3143 PO Box 2500 Malvern VIC 3144 Australia Tel: +61 3 9248 3100 Fax: +61 3 9248 3400 Web: www.skmconsulting.com COPYRIGHT: The concepts and information contained in this document are the property of Sinclair Knight Merz Pty Ltd. Use or copying of this document in whole or in part without the written permission of Sinclair Knight Merz constitutes an infringement of copyright. SALINITY MONITORING IN THE MOORABOOL, BARWON, LAKE CORANGAMITE AND OTWAY BASINS Contents 1. Introduction 1 1.1 Study area 1 1.2 Project scope 3 1.3 Report structure 3 2. Framework for water quality monitoring 4 2.1 Consideration of monitoring program objectives 4 2.2 Consideration of study design 4 2.3 Summary 6 3. Data availability 7 3.1 Moorabool Basin 8 3.2 Barwon Basin 9 3.3 Lake Corangamite Basin 10 3.4 Otway Coast Basin 10 4. Method of site selection and data analysis 12 4.1 Selection of “key points” 12 4.2 Method of data analysis 16 5. Results 18 5.1 Moorabool Basin 18 5.2 Barwon Basin 26 5.3 Lake Corangamite Basin 33 5.4 Otway Coast Basin 40 6. Discussion 49 6.1 Monitoring of salinity target areas 49 6.2 Monitoring of “end-of-valley” type points 55 7. Conclusions 59 7.1 Recommendations for salinity target areas 59 7.2 Recommendations for “end-of-valley” type points 59 7.3 Further recommendations 59 8. References 60 Appendix A Hydrographic monitoring sites 61 Appendix B Outliers removed from spot salinity records 65 I:\WCMS\Projects\WC03289\Deliverables\D04ral_Final_Report.doc PAGE i SALINITY MONITORING IN THE MOORABOOL, BARWON, LAKE CORANGAMITE AND OTWAY BASINS Document history and status Revision Date issued Reviewed by Approved by Date approved Revision type Draft A 24-Jun-05 B Neal R Lett 24-Jun-05 Internal draft Draft A 28-Jun-05 G Hoxley R Lett 28-Jun-05 Internal draft Draft A 30-Jun-05 R Lett 30-Jun-05 Draft for release Final 25-July-05 G Hoxley R Lett 25-July-05 Final for release Distribution of copies Revision Copy no Quantity Issued to Draft A 1 (pdf) 1 Felicia Choo (CCMA) Final 1 (pdf) 1 Felicia Choo (CCMA) Printed: 25 July 2005 Last saved: 25 July 2005 04:01 PM File name: I:\WCMS\Projects\WC03289\Deliverables\D04ral_Final_Report.doc Author: Rebecca Lett Project manager: Rebecca Lett Name of organisation: Corangamite Catchment Management Authority Benchmarking saline flows in key rivers and streams for resource condition target Name of project: development Name of document: Salinity monitoring in the Moorabool, Barwon, Lake Corangamite and Otway Basins Document version: Final Project number: WC03289 I:\WCMS\Projects\WC03289\Deliverables\D04ral_Final_Report.doc PAGE ii SALINITY MONITORING IN THE MOORABOOL, BARWON, LAKE CORANGAMITE AND OTWAY BASINS 1. Introduction The co-ordinated management of salinity within the Corangamite area has gone through a number of stages of development. In 1992 a publication was launched, called “Restoring the Balance”, as part of a salinity initiative by the State Government. In October 2001, the Commonwealth Government and the state of Victoria entered into an agreement for the implementation of a National Action Plan (NAP) for Salinity and Water Quality and in 2002 the Corangamite Catchment Management Authority launched a Catchment Strategy for the Corangamite Region. Among the key commitments of the NAP was a plan to establish regional targets and national standards for natural resource management, particularly for salinity and water quality (Commonwealth of Australia, 2001). The Catchment Management Authorities were designated the task of coordinating the NAP at a regional level. Responsibilities included target setting, community consultation and annual reporting. Monitoring of natural assets is an integral part of the NAP. SKM has been engaged by the Corangamite Catchment Management Authority (CCMA) to collate and analyse all available stream salinity data for the major basins in the CCMA area. The CCMA has instructed that the flow weighted historical salinity should be defined at “key points” and that data sets should be grouped by basin. “Key points” are to include an “end-of-valley” type point that can be used as a baseline to indicate the overall resource condition of the stream from a salinity point of view. From this assessment, the CCMA requires general conclusions to be drawn as to the adequacy of salinity monitoring for the purpose of defining resource condition targets (RCTs). This report documents the findings of the salinity monitoring investigation. Within the following sections the study area (Section 1.1) and project scope are defined (Section 1.2). 1.1 Study area The basins within the CCMA area are the Moorabool, Barwon, Lake Corangamite and Otway Coast. These basins are all south of the Great Dividing Range and, as such, generally drain towards Bass Strait. The Lake Corangamite Basin however constitutes a terminal system, with streams generally flowing north to south into local lakes. The Moorabool River drains an area of 2,170 km2 (Department of Water Resources Victoria, 1989), from the Wombat State Forest, near Ballan, to the Bass Strait. In its upper reaches the river is divided into two branches, called the West Branch and East Branch. At Geelong, the Moorabool River meets the Barwon River. The river is highly regulated; the major reservoirs within the Moorabool Basin are Lal Lal Reservoir, Moorabool Reservoir and Bostock Reservoir. Located within the Moorabool Basin is the Little River, which drains in a south-easterly direction, from the Brisbane Ranges to Port Phillip Bay. I:\WCMS\Projects\WC03289\Deliverables\D04ral_Final_Report.doc PAGE 1 SALINITY MONITORING IN THE MOORABOOL, BARWON, LAKE CORANGAMITE AND OTWAY BASINS The Barwon Basin covers an area of 3,880 km2 (Department of Water Resources Victoria, 1989) and has its headlands in the Otway Ranges. The River drains to the north while, at the opposite end of the basin, the Leigh River flows south from Ballarat. The two rivers meet at Inverleigh, where the Barwon River turns east and flows towards the Bass Strait. The Barwon River is also highly regulated; the major reservoirs are the West Barwon Reservoir, Wurdee Boluc Reservoir (off- stream) and the White Swan Reservoir. The Lake Corangamite Basin covers an area of 4,190 km2 (Department of Water Resources Victoria, 1989). The basin is land-locked; the drainage system flows to a number of terminal lakes, the largest of which is Lake Corangamite. The streams within the Lake Corangamite Basin include the Woady Yaloak River, Pirron Yallock Creek, Mundy Gully Creek, the Gnarkeet Chain of Ponds, Deans Creek and Barongarook Creek. Water is transferred from the Lake Corangamite Basin into the Barwon River Basin at two points – from Black Bridge Pool to Warrambine Creek via the Woady Yaloak Diversion Channel and from Lake Colac to Birregurra Creek. The Otway Coast Basin drains the land south of the Otway Ranges and an area to the west – a total area equalling 3,900 km2. Several streams flow in a coastal direction, including the Curdies, Gellibrand and Aire Rivers. There are no major storages within the Otway Coast Basin, although there are a number of pump stations and weirs which supply water to towns, both in and outside the basin (Department of Water Resources Victoria, 1989). The principle landuses within the CCMA area are livestock grazing and dryland agriculture: Table 1-1 Landuse within the basins of the CCMA area (CCMA, 2003). Landuse Morrabool Barwon River Lake Otway Coast River Basin Basin Corangamite Basin Basin Nature conservation 4.5 2.0 12.0 14.5 Minimal user (mainly Crown land) 11.7 3.0 1.5 8.3 Forestry 3.3 9.0 2.5 22.4 Livestock grazing 39.1 42.3 38.9 26.5 Dryland agriculture 33.7 35.9 43.0 26.6 Irrigated agriculture 0.4 0.5 0.6 0.4 Built environment 7.3 6.8 1.1 0.6 Water 0.0 0.3 0.4 0.2 Total 100.0 100.0 100.0 100.0 I:\WCMS\Projects\WC03289\Deliverables\D04ral_Final_Report.doc PAGE 2 SALINITY MONITORING IN THE MOORABOOL, BARWON, LAKE CORANGAMITE AND OTWAY BASINS 1.2 Project scope The objectives of the current study are: To collate and analyse all available stream salinity data for the major basins in the CCMA area; To identify "key points" within each basin for resource condition target setting; To define at each “key point” the historic flow weighted salinity; and To ascertain the suitability of the current monitoring network for the purpose of resource condition target development. For the purpose of the current study, "key points" are defined as the stream1 monitoring sites of relevance to the proposed resource condition targets for interim salinity management target locations as well as an “end-of-valley” type point for each of the landscape zones within the CCMA basins. 1.3 Report structure The Australian and New Zealand Environment and Conservation Council have developed guidelines for water quality monitoring and reporting (ANZECC, 2000). These guidelines are discussed in Chapter 2 of this report. In Chapter 3, salinity monitoring sites within the CCMA area are identified. Sites are listed by basin. In Chapter 4 "key points" are identified and the method for calculating flow weighted salinity is described.