DPIW – SURFACE WATER MODELS RUBICON RIVER CATCHMENT Rubicon River Surface Water Model Hydro Tasmania Version No: 2.0 DOCUMENT INFORMATION JOB/PROJECT TITLE Tascatch Variation 2 -Surface Water Models CLIENT ORGANISATION Department of Primary Industries and Water CLIENT CONTACT Bryce Graham DOCUMENT ID NUMBER WR 2007/066 JOB/PROJECT MANAGER Mark Willis JOB/PROJECT NUMBER E202869/P205357 Document History and Status Revision Prepared Reviewed Approved Date Revision by by by approved type 1.0 J Bennett M. Willis C. Smythe Dec 2007 FINAL 2.0 J. Bennett M. Willis C. Smythe April 2008 FINAL Current Document Approval PREPARED BY James Bennett Water Resources Mngt Sign Date REVIEWED BY Mark Willis Water Resources Mngt Sign Date APPROVED FOR Crispin Smythe SUBMISSION Water Resources Mngt Sign Date Current Document Distribution List Organisation Date Issued To DPIW April 2008 Bryce Graham The concepts and information contained in this document are the property of Hydro Tasmania. This document may only be used for the purposes of assessing our offer of services and for inclusion in documentation for the engagement of Hydro Tasmania. Use or copying of this document in whole or in part for any other purpose without the written permission of Hydro Tasmania constitutes an infringement of copyright. i Rubicon River Surface Water Model Hydro Tasmania Version No: 2.0 EXECUTIVE SUMMARY This report is part of a series of reports which present the methodologies and results from the development and calibration of surface water hydrological models for 25 catchments (Tascatch – Variation 2) under both current and natural flow conditions. This report describes the results of the hydrological model developed for the Rubicon River catchment. A model was developed for the Rubicon River catchment that facilitates the modelling of flow data for three scenarios: • Scenario 1 – No entitlements (Natural Flow); • Scenario 2 – with Entitlements (with water entitlements extracted); • Scenario 3 - Environmental Flows and Entitlements (Water entitlements extracted, however low priority entitlements are limited by an environmental flow threshold). The results from the scenario modelling allow the calculation of indices of hydrological disturbance. These indices include: • Index of Mean Annual Flow • Index of Flow Duration Curve Difference • Index of Seasonal Amplitude • Index of Seasonal Periodicity • Hydrological Disturbance Index The indices were calculated using the formulas stated in the Natural Resource Management (NRM) Monitoring and Evaluation Framework developed by SKM for the Murray-Darling Basin (MDBC 08/04). A user interface is also provided that allows the user to run the model under varying catchment demand scenarios. This allows the user to add further extractions to catchments and see what effect these additional extractions have on the available water in the catchment of concern. The interface provides sub-catchment summary of flow statistics, duration curves, hydrological indices and water entitlements data. For information on the use of the user interface refer to the Operating Manual for the NAP Region Hydrological Models (Hydro Tasmania 2004). ii Rubicon River Surface Water Model Hydro Tasmania Version No: 2.0 CONTENTS EXECUTIVE SUMMARY ii 1. INTRODUCTION 1 2. CATCHMENT CHARACTERISTICS 2 3. DATA COMPILATION 4 3.1 Climate data (Rainfall & Evaporation) 4 3.2 Advantages of using climate DRILL data 4 3.3 Transposition of climate DRILL data to local catchment 5 3.4 Comparison of Data Drill rainfall and site gauges 7 3.5 Streamflow data 8 3.6 Irrigation and water usage 9 3.6.1 Estimation of unlicensed (small) farm dams 16 3.7 Environmental flows 17 4. MODEL DEVELOPMENT 20 4.1 Sub-catchment delineation 20 4.2 Hydstra Model 20 4.3 AWBM Model 22 4.3.1 Channel Routing 24 4.4 Model Calibration 25 4.4.1 Factors affecting the reliability of the model calibration. 32 4.4.2 Model Accuracy - Model Fit Statistics 33 4.4.3 Model accuracy across the catchment 36 5. MODEL RESULTS 39 5.1.1 Indices of hydrological disturbance 39 6. FLOOD FREQUENCY ANALYSIS 42 7. REFERENCES 44 7.1 Personal Communications 45 8. GLOSSARY 46 APPENDIX A 48 iii Rubicon River Surface Water Model Hydro Tasmania Version No: 2.0 LIST OF FIGURES Figure 2-1 Sub-catchment boundaries 3 Figure 3-1 Climate Drill Site Locations 6 Figure 3-2 Rainfall and Data Drill Comparisons 8 Figure 3-3 WIMS Water Allocations 15 Figure 4-1 Hydstra Model Schematic 21 Figure 4-2 Two Tap Australian Water Balance Model Schematic 24 Figure 4-3 Monthly Variation of CapAve Parameter 28 Figure 4-4 Daily time series comparison (ML/d) – Rubicon River - Good fit. 29 Figure 4-5 Daily time series comparison (ML/d) – Rubicon River – Good fit. 29 Figure 4-6 Daily time series comparison (ML/d) – Rubicon River – Good fit. 30 Figure 4-7 Monthly time series comparison – volume (ML) 30 Figure 4-8 Long term average monthly, seasonal and annual comparison plot 31 Figure 4-9 Duration Curve – Daily flow percentage difference 35 Figure 4-10 Duration Curve – Monthly volume percentage difference 35 Figure 4-11 Time Series of Monthly Volumes- Site 17201 37 Figure 4-12 Time Series of Monthly Volumes- SubC1_c 38 Figure 5-1 Daily Duration Curve 39 Figure 6-1 Modelled and Observed Flood Frequency Plot – Rubicon at Tidal Limit 43 Figure A-1 Forth catchment – monthly volumes at secondary site. 50 Figure A-2 George catchment – monthly volumes at secondary site. 50 Figure A-3 Leven catchment – monthly volumes at secondary site. 51 Figure A-4 Swan catchment – monthly volumes at secondary site. 51 Figure A-5 Montagu catchment – monthly volumes at secondary site. 52 iv Rubicon River Surface Water Model Hydro Tasmania Version No: 2.0 LIST OF TABLES Table 3.1 Data Drill Site Locations 7 Table 3.2 Potential calibration sites 9 Table 3.3 Assumed Surety of Unassigned Records 10 Table 3.4 Sub Catchment High and Low Priority Entitlements 11 Table 3.5 Average capacity for dams less than 20 ML by Neal et al (2002) 17 Table 3.6 Environmental Flows 18 Table 4.1 Boughton & Chiew, AWBM surface storage parameters 22 Table 4.2 Hydstra/TSM Modelling Parameter Bounds 25 Table 4.3 Adopted Calibration Parameters 27 Table 4.4 Long term average monthly, seasonal and annual comparisons 31 Table 4.5 Model Fit Statistics 33 2 Table 4.6 R Fit Description 34 Table 5.1 Hydrological Disturbance Indices 40 Table A-1 Model performance at secondary sites 53 v Rubicon River Surface Water Model Hydro Tasmania Version No: 2.0 1. INTRODUCTION This report forms part of a larger project commissioned by the Department of Primary Industries and Water (DPIW) to provide hydrological models for 25 regional catchments (Tascatch – Variation 2). The main objectives for the individual catchments are: • To compile relevant data required for the development and calibration of the hydrological model (Australian Water Balance Model, AWBM) for the Rubicon River catchment; • To source over 100 years of daily time-step rainfall and streamflow data for input to the hydrologic model; • To develop and calibrate each hydrologic model, to allow running of the model under varying catchment demand scenarios; • To develop a User Interface for running the model under these various catchment demand scenarios; • Prepare a report summarising the methodology adopted, assumptions made, results of calibration and validation and description relating to the use of the developed hydrologic model and associated software. 1 Rubicon River Surface Water Model Hydro Tasmania Version No: 2.0 2. CATCHMENT CHARACTERISTICS The Rubicon catchment is located in central North Tasmania and discharges into the bay of Port Sorell. The Rubicon River has a catchment area of 263.2 km 2, however the Rubicon surface model covers a much larger area – 572.4 km 2 - as it also simulates flow in smaller catchments that adjoin (but do not flow into) the Rubicon (Figure 2-1). To differentiate between the Rubicon river catchment area and the entire catchment area of the model, the former will be called the ‘Rubicon catchment’ and the latter the ‘model catchment’ henceforth. The larger streams (other than the Rubicon) covered by in the model catchment area are Pardoe Creek, which discharges into Bass Strait, and Franklin Rivulet, Branchs Creek and Browns Creek, which discharge into Port Sorrell. The Panatana River (north-west of the Rubicon) is not accounted for in this model as a DPIW surface water model of this catchment already exists (see Willis and Peterson 2007). The headwaters of the Rubicon catchment start in the small, forested hills that rise to 500 m ASL in the south-east of the catchment. The eastern half of the model catchment area is forested with both natural and plantation forests, while the western half of the model catchment is mainly used for cropping and other agriculture. The Rubicon catchment is unusual in that both the upper and lower parts of the catchment are heavily exploited for agriculture, while the middle of the catchment is forested. (It is more usual that only the lower part of a catchment, where streamflows are higher and richer alluvial soils occur, is suitable for farming.) Large volumes of water are extracted from the Rubicon and surrounding creeks for agriculture and these water extractions can result in significant localised reductions in streamflow. The model catchment is dry relative to many Tasmanian catchments, receiving 700 mm in the north-east to 1000 mm in the hills in the South (Figure 2-1). There are 291 registered (current) entitlements for water extraction registered on the Water Information Management System (WIMS July 2007). Most of these extractions are concentrated in only a few sub-catchments (Figure 3-3). Licenced extractions relate mainly to agriculture. The largest extraction entitlement is 1860 ML for a large irrigation dam in the South of the Rubicon Catchment.