DPIW – SURFACE WATER MODELS CLYDE RIVER CATCHMENT Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 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 2007/061 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 M. Willis J. Peterson C. Smythe Dec 2007 Final 1.1 M. Willis J. Peterson C. Smythe July 2008 Final Current Document Approval PREPARED BY Mark Willis Water Resources Mngt Sign Date REVIEWED BY Jayson Peterson Water Resources Mngt Sign Date APPROVED FOR Crispin Smythe SUBMISSION Water Resources Mngt 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. 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 Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 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 Clyde River catchment. A model was developed for the Clyde 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 Clyde River model completed for this project produces disproportionately higher flows when run under Scenario 1 (Natural) than other catchments within the Clyde model. This is particularly evident when comparing Scenario 1 to either Scenario 2 or Scenario 3. This is mostly due to an increased yield from the Lake Crescent & Lake Sorell area. It is recommended that additional work be undertaken to assess the yield contribution of the Lake Crescent and Lake Sorell catchment pre and post dam construction. This will allow the current model output to be confirmed and if necessary calibration adjustments to be undertaken. 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). ii Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 A user interface is 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). iii Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 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 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 19 4.1 Sub-catchment delination 19 4.2 Hydstra Model 19 4.2.1 Flow downstream Lake Crescent and Lake Sorell 21 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. 33 4.4.2 Model Accuracy - Model Fit Statistics 34 4.4.3 Model accuracy across the catchment 37 5. MODEL RESULTS 39 5.1.1 Indices of hydrological disturbance 40 6. FLOOD FREQUENCY ANALYSIS 42 7. REFERENCES 44 7.1 Personal Communications 45 8. GLOSSARY 46 APPENDIX A 48 iv Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 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 20 Figure 4-2 Australian Water Balance Model Schematic 24 Figure 4-3 Monthly Variation of CapAve Parameter 28 Figure 4-4 Daily time series (ML/d) – Clyde River - Poor fit. 29 Figure 4-5 Daily time series (ML/d) – Clyde River – Good fit. 30 Figure 4-6 Daily time series (ML/d) – Clyde River – Good fit. 30 Figure 4-7 Monthly time series comparison – volume (ML) 31 Figure 4-8 Long term average monthly, seasonal and annual comparison plot 31 Figure 4-9 Duration Curve – Daily flow percentage difference 36 Figure 4-10 Duration Curve – Monthly volume percentage difference 37 Figure 4-11 Time Series of Monthly Volumes- Clyde River at Bothwell 38 Figure 5-1 Daily Duration Curve 39 Figure 6-1 Modelled and Observed Flood Frequency Plot – Clyde River above Hamilton 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 v Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 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 12 Table 3.5 Average capacity for dams less than 20 ML by Neal et al (2002) 17 Table 3.6 Cease-to-take flows (ML/day measured at Bothwell) 17 Table 3.7 Environmental Flows 18 Table 4.1 Long term average flows - Clyde d/s Lake Crescent 22 Table 4.2 Boughton & Chiew, AWBM surface storage parameters 23 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 32 Table 4.6 Model Fit Statistics 35 2 Table 4.7 R Fit Description 35 Table 5.1 Hydrological Disturbance Indices 40 Table A-1 Model performance at secondary sites 53 vi Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 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 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 Clyde 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 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 Clyde River Surface Water Model Hydro Tasmania Version No: 1.1 2. CATCHMENT CHARACTERISTICS The Clyde River catchment is located in Southern Tasmania. It has a catchment area of 1131 km 2 and is a tributary of the Derwent River. The headwaters of the catchment originate in Lake Sorell and are fed by runoff from Tasmania’s Central Plateau at an elevation of around 1100m AHD. This portion of the catchment is virtually unpopulated except for a few isolated fishing shacks and is predominately eucalypt forest. The middle and lower parts of the catchment are highly modified due to the control of the flow from Lake Crescent for irrigation by the Clyde River Trust. The vegetation is predominately pasture with pockets of native eucalypt forest on terrain unsuitable for agriculture. The major settlements in the Clyde catchment are the two historic towns of Bothwell and Hamilton, which both rely on the Clyde River for their water supply. Variability in the annual rainfall total across this catchment is significant, mainly due to the changes in elevation and the varied exposure to the dominant westerly weather pattern. The lower catchment around Hamilton receives a typical annual rainfall of around 500mm and the upper catchment around Lake Sorell around 800mm. There are 62 registered (current) entitlements for water extraction listed on the Water Information Management System (WIMS July 2007). Most of these extractions are concentrated in the lower sub-catchments and mainly relate to irrigation. The largest WIMS extraction entitlement is 5400 ML associated with a large farm dam on Weasel Plains Creek.