Tarwin Water Supply Catchment Water Quality Management Plan
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Tarwin Water Supply Catchment Water Quality Management Plan Report Prepared for South Gippsland Water and South Gippsland Shire Council By Ecos Environmental Consulting and Water Technology November 2014 Document Information Revision Status Prepared by Issued to Date Approved 1.0 TOC Draft Nick O’Connor Kerry Matthews 20 March 2014 Nick O’Connor and Sarah Law 1.1 Draft Nick O’Connor Kerry Matthews 9 October 2014 Nick O’Connor and Sarah Law 1.2 Final Nick O’Connor Kerry Matthews 26 November Nick O’Connor and Sarah Law 2014 Created by Ecos Environmental Consulting Pty Ltd ABN 11 086 102 383, ACN 086 102 383 Suite 3, Level 1, 339 Whitehorse Rd, Balwyn, Victoria 3103 Mail PO Box 1064G North Balwyn Victoria 3104 Tel +61 3 9830 7740 Fax +61 3 9830 7741 Mob 0408 520 579 (Nick) Email [email protected] Web www.ecosec.com.au File name K:\Ecos Projects\1251 - SGW Tarwin River Catchment WQ RA\Report - Final\Tarwin WS_CMP Final 26Nov2014.docx+ Client Kerry Matthews Name of organisation South Gippsland Water Name of project Tarwin Water Supply Catchment Modelling Study Name of document Tarwin WS_CMP Final 26Nov2014 Document version 1.2 Cover Images and logos are © Ecos Environmental Consulting Sensitivity This document and the information, ideas, concepts, methodologies, technologies and other material it contains remain the intellectual property of Ecos Environmental Consulting P/L, South Gippsland Water and South Gippsland Shire Council. The document is not to be copied without the express permission of at least one of the above parties. REPORT: Tarwin Water Supply Catchment Water Quality Management Plan Ecos Environmental Consulting Pty Ltd and Water Technology Pty Ltd 1251: 2014 2 Table of Contents 1 Introduction ................................................................................................................ 20 1.1. Background ...................................................................................................... 21 1.2. Objectives of the Tarwin Water Supply Catchment Management Plan .......... 21 1.2.1. Modelling objectives .................................................................................... 22 1.3. Institutional Framework and the Role of the Tarwin Water Supply Catchment Management Plan ......................................................................................................... 22 1.4. Developing the Management Plan .................................................................. 25 2 Tarwin River Water Supply Catchment description ................................................... 26 2.1. The Tarwin Water Supply Catchment.............................................................. 26 2.1.1. Land use ...................................................................................................... 27 2.1.1.1. Average property size ......................................................................... 29 2.1.2. Water Supply Systems ................................................................................ 29 2.2. Water quality issues in the Tarwin River Water Supply Catchment ................ 31 2.2.1. On-site wastewater management ............................................................... 31 2.2.1.1. Current wastewater management ...................................................... 31 2.2.2. Further development of unsewered residential areas ................................. 33 2.2.2.1. South Gippsland Shire Council Housing and Settlement Strategy .... 33 2.2.2.2. Baw Baw Shire Council Settlement Management Plan ..................... 33 2.2.2.3. Latrobe City Council settlement planning ........................................... 34 2.2.3. Densities of unsewered dwellings ............................................................... 34 2.2.3.1. Farming Zone ..................................................................................... 34 2.2.3.2. Future development potential ............................................................. 36 2.2.3.3. Other planning zones ......................................................................... 38 2.2.4. Grazing pasture landuse and stock access to waterways .......................... 39 2.2.5. Point source discharges .............................................................................. 40 3 Modelling and consultation approaches .................................................................... 41 3.1. Stakeholder Working Group and Workshops .................................................. 41 3.1.1. First Working Group meeting ...................................................................... 41 3.1.2. Second Working Group meeting: Scenario Development .......................... 42 3.1.3. Compilation, analysis and presentation of modelling results ...................... 42 3.1.4. Final Working Group meeting: Presentation of draft modelling report ........ 42 4 Model setup ............................................................................................................... 43 4.1. About the Source model and its structure ....................................................... 43 REPORT: Tarwin Water Supply Catchment Water Quality Management Plan Ecos Environmental Consulting Pty Ltd and Water Technology Pty Ltd 1251: 2014 3 4.2. A description of the modelling approach ......................................................... 44 4.2.1. Constituents for modelling: e.g. nutrients, microbial pathogens, pesticides, etc. 44 4.2.2. Source outputs and scenario definition ....................................................... 44 4.3. Specifying network and sub-catchments ......................................................... 45 4.4. Delineation of subcatchments for modelling .................................................... 45 4.5. Specifying constituents .................................................................................... 48 4.5.1. Suspended Sediment .................................................................................. 48 4.5.2. Nutrients ...................................................................................................... 48 4.5.3. Waterborne pathogens ................................................................................ 49 4.6. Specifying functional units ............................................................................... 50 4.7. Choice of rainfall-runoff model ......................................................................... 51 4.8. Assigning constituent generation models ........................................................ 53 4.9. Assigning filter models ..................................................................................... 53 4.10. Assigning link models ...................................................................................... 54 4.11. Assigning node models ................................................................................... 54 4.12. Rainfall-runoff model data input ....................................................................... 54 4.12.1. Data availability ....................................................................................... 54 4.12.2. Stream flow data ..................................................................................... 56 4.13. Water Quality model data input ....................................................................... 57 4.14. Assigning rainfall-runoff model parameters ..................................................... 58 4.15. Assigning constituent generation parameters ................................................. 58 4.15.1. Suspended Solids & Nutrients ................................................................ 58 4.15.2. Pathogen generation rates...................................................................... 59 4.15.3. Base Case DWC/EMC Values ................................................................ 59 4.16. Assigning node parameters ............................................................................. 59 4.17. Runoff model calibration .................................................................................. 61 4.18. Runoff model verification ................................................................................. 62 4.18.1. Mean annual discharge ........................................................................... 63 4.18.2. Daily flow duration curves ....................................................................... 63 4.18.3. Extractions .............................................................................................. 64 4.18.4. Conclusion – runoff model verification .................................................... 65 4.19. Water Quality model verification ...................................................................... 65 REPORT: Tarwin Water Supply Catchment Water Quality Management Plan Ecos Environmental Consulting Pty Ltd and Water Technology Pty Ltd 1251: 2014 4 4.19.1. Leongatha Verification ............................................................................ 65 4.19.2. Meeniyan Verification .............................................................................. 67 4.19.3. Conclusion – water quality model verification ......................................... 68 5 Key Management Areas and related programs ......................................................... 69 5.1. Vision and Key Guiding Principles and Key Management Areas (KMA’s) ...... 69 5.1.1. Best Management Practice Programs ........................................................ 71 5.1.2. KMA 1: Riparian and