DPIW – SURFACE WATER MODELS EMU CATCHMENT Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 DOCUMENT INFORMATION JOB/PROJECT TITLE DPIW – Surface Water Models CLIENT ORGANISATION DPIW CLIENT CONTACT Bryce Graham DOCUMENT ID NUMBER WR 2007/21 JOB/PROJECT MANAGER Mark Willis JOB/PROJECT NUMBER E200690/P202617 Document History and Status Revision Prepared by Reviewed Approved Date Revision by by approved type 1.0 D. Trebilcock F. Ling C. Smythe May 2007 Final 2.0 M. Willis F. Ling C. Smythe Sept 2007 Final 2.1 M. Willis F. Ling C. Smythe July 2008 Final Current Document Approval PREPARED BY Mark Willis SRE WRM Sign Date REVIEWED BY Fiona Ling SRE WRM Sign Date APPROVED FOR Crispin Smythe SUBMISSION SRE WRM Sign Date Current Document Distribution List Organisation Date Issued To DPIW July 2008 Bryce Graham The concepts and information contained in this document are the property of Hydro Tasmania Consulting. This document may only be used for the purposes for which, and upon the conditions, the report is supplied. Use or i Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 copying of this document in whole or in part for any other purpose without the written permission of Hydro Tasmania Consulting constitutes an infringement of copyright. 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 26 catchments under both current and natural flow conditions. This report describes the results of the hydrological model developed for the Emu Catchment. A model was developed for the Emu 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. It 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 a 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 Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 iii Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 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 Data Drill Data 4 3.3 Transposition of Data Drill Data to Local Catchment 5 3.4 Comparison of Data Drill Rainfall and Site Gauges 5 3.5 Streamflow Data 7 3.6 Irrigation and Water Usage 8 3.7 Estimation of unlicensed dams 14 3.8 Environmental Flows 15 4. MODEL DEVELOPMENT 17 4.1 Sub-catchment Delineation 17 4.2 Hydstra Model 17 4.2.1 Storages 18 4.2.2 Inter-Basin Transfer – Talbot’s Lagoon via Wey River 20 4.2.3 Inter-Basin Transfer – Guide Reservoir 21 4.3 AWBM Model 22 4.3.1 Channel Routing 24 4.4 Model Calibrations 25 4.4.1 Factors affecting the reliability of the model calibration. 32 4.4.2 Model Accuracy - Model Fit Statistics 34 4.4.3 Model accuracy across the catchment 37 4.5 Model Results 39 4.5.1 Indices of hydrological disturbance 40 4.6 Flood Frequency Analysis 41 5. REFERENCES 43 5.1 Personal Communications 43 6. GLOSSARY 44 APPENDIX A 46 iv Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 LIST OF FIGURES Figure 2-1 Sub-catchment boundaries 3 Figure 3-2 Rainfall and Data Drill Comparisons 7 Figure 3-3 WIMS Water Allocations 13 Figure 4-1 Hydstra model schematic 18 Figure 4-2 Companion Reservoir threshold flow for operation of Wey River transfer 21 Figure 4-3 Australian Water Balance Model schematic 24 Figure 4-4 Monthly variation of CapAve parameter 28 Figure 4-5 Daily time series comparison (ML/d). Good fit. 29 Figure 4-6 Daily time series comparison (ML/d). Good fit. 29 Figure 4-7 Daily time series comparison (ML/d). Good fit. 30 Figure 4-8 Time series of monthly volumes 30 Figure 4-9 Long term average monthly, seasonal and annual comparison plot 31 Figure 4-10 Duration Curve – Daily flow percentage difference 36 Figure 4-11 Duration Curve – Monthly volume percentage difference 36 Figure 4-12 Time Series of Monthly Volumes- Site 14203 38 Figure 4-13 Time Series of Monthly Volumes- Site 14219 38 Figure 4-14 Daily duration curve 39 Figure 4-15 Modelled and observed flood frequency plot 42 Figure A-1 Forth catchment – monthly volumes at secondary site. 48 Figure A-2 George catchment – monthly volumes at secondary site. 48 Figure A-3 Leven catchment – monthly volumes at secondary site. 49 Figure A-4 Swan catchment – monthly volumes at secondary site. 49 Figure A-5 Montagu catchment – monthly volumes at secondary site. 50 v Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 LIST OF TABLES Table 3-1 Data Drill site locations 5 Table 3-2 Streamflow gauge locations 7 Table 3-3 Assumed surety of unassigned records 9 Table 3-4 Sub-catchment high and low priority entitlements. Monthly demand (ML) for each sub-catchment and month. 11 Table 3-5 Average capacity for dams less than 20 ML by Neal et al (2002) 15 Table 3-6 Environmental flows (ML/d) at each sub-catchment 16 Table 4-1 Details of significant storages 19 Table 4.2 Boughton & Chiew, AWBM surface storage parameters 22 Table 4.3 Hydstra/TSM Modelling Parameter Bounds 25 Table 4-4 Adopted calibration parameters 27 Table 4-5 Long term average monthly, seasonal and annual comparisons (ML/d)32 Table 4-6 Model fit statistics 34 2 Table 4.7 R Fit Description 35 Table 4-8 Hydrological Disturbance Indices 40 Table A-1 Model performance at secondary sites 51 vi Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 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 26 regional catchments. 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 Emu Catchment; • To source over 100 years of daily time-step rainfall and streamflow data for input to the hydrologic model; • To develop and calibrate the hydrologic model under both natural and current catchment conditions; • To develop a User Interface for running the model under varying 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 Emu Surface Water Model Hydro Tasmania Consulting Version No: 2.1 2. CATCHMENT CHARACTERISTICS The Emu River is located in north-west Tasmania and discharges into Bass Strait at Burnie (Emu Bay). The River descends from St. Valentines Peak (elevation approximately 1100 m AHD). The upper reaches of the catchment, south of Highclere, are predominantly forested and the catchment is characterised by forestry operations and the production of wood chips and paper. In the lower reaches, north of Highclere, there are some agricultural areas and the built-up area along the coast (Burnie). The catchment area is 247 km . The Emu River is impounded high in its catchment by the Companion Reservoir. North Forests Burnie operate a water race and siphon which transfers water from the Wey River to the head of the Emu River above Companion Reservoir. Above Hampshire the Emu River is joined by the significant tributaries Old Park River and Loud Water River. Below Hampshire, the Emu River is joined by significant tributaries Wollastonite Creek, Osborne Creek and Tittie Gee Creek. The Tittie Gee Creek is impounded at Lake Kara. The Pet River and Glance Creek join the Emu River before Burnie. The Pet River is impounded at Ridgley by the Pet Reservoir. Romaine Creek flows along the north-west side of the catchment through Burnie and discharges into Emu Bay directly. Variability in the annual rainfall across the catchment is pronounced due to the changes in elevation and exposure to the dominant westerly weather pattern. Annual average rainfall ranges from 1000 mm at the coast to 1600-1800 mm at the top of the catchment. For modelling purposes, the Emu Catchment was divided into 26 sub-catchments. The delineation shown in Figure 2-1 includes one sub-catchment (SC26) which does not drain through the Emu River but directly to the sea (Romaine Creek). There are 130 registered (current) entitlements for water extraction on the Water Information Management System (WIMS Dec 2006). Most of these predominantly lie in the lower part of the catchment north of Highclere. Many of the upper sub- catchments (south of Highclere) have no registered WIMS entitlements.