DPIW – SURFACE WATER MODELS DETENTION AND BLACK RIVER CATCHMENTS Detention and Black Rivers Surface Water Model Hydro Tasmania Version No: FINAL 1.0 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 2007/069 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 Jan 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 Jan 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 Detention and Black Rivers Surface Water Model Hydro Tasmania Version No: FINAL 1.0 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 Detention and Black River catchments. A model was developed for the Detention and Black 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 Detention and Black Rivers Surface Water Model Hydro Tasmania Version No: FINAL 1.0 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 17 3.7 Environmental flows 18 4. MODEL DEVELOPMENT 21 4.1 Sub-catchment delineation 21 4.2 Hydstra Model 21 4.3 AWBM Model 23 4.3.1 Channel Routing 25 4.4 Model Calibration 26 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 40 5.1.1 Indices of hydrological disturbance 40 6. FLOOD FREQUENCY ANALYSIS 43 7. REFERENCES 45 7.1 Personal Communications 46 8. GLOSSARY 47 APPENDIX A 49 iii Detention and Black Rivers Surface Water Model Hydro Tasmania Version No: FINAL 1.0 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 16 Figure 4-1 Hydstra Model Schematic 22 Figure 4-2 Two Tap Australian Water Balance Model Schematic 25 Figure 4-3 Monthly Variation of CapAve Parameter 29 Figure 4-4 Daily time series comparison (ML/d) – Black River - Good fit. 30 Figure 4-5 Daily time series comparison (ML/d) – Black River – Good fit. 30 Figure 4-6 Daily time series comparison (ML/d) – Black River – Good fit. 31 Figure 4-7 Monthly time series comparison – volume (ML) 31 Figure 4-8 Long term average monthly, seasonal and annual comparison plot 32 Figure 4-9 Duration Curve – Daily flow percentage difference 36 Figure 4-10 Duration Curve – Monthly volume percentage difference 36 Figure 4-11 Time Series of Monthly Volumes- Site 14226 38 Figure 4-12 Time Series of Monthly Volumes- SC 9_e 39 Figure 5-1 Daily Duration Curve 40 Figure 6-1 Modelled and Observed Flood Frequency Plot - Black River at South Forest (site 14213) 44 Figure A-1 Forth catchment – monthly volumes at secondary site. 51 Figure A-2 George catchment – monthly volumes at secondary site. 51 Figure A-3 Leven catchment – monthly volumes at secondary site. 52 Figure A-4 Swan catchment – monthly volumes at secondary site. 52 Figure A-5 Montagu catchment – monthly volumes at secondary site. 53 iv Detention and Black Rivers Surface Water Model Hydro Tasmania Version No: FINAL 1.0 LIST OF TABLES Table 3.1 Data Drill Site Locations 7 Table 3.2 Observed flow 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) 18 Table 3.6 Environmental Flows 19 Table 4.1 Boughton & Chiew, AWBM surface storage parameters 23 Table 4.2 Hydstra/TSM Modelling Parameter Bounds 26 Table 4.3 Adopted Calibration Parameters 28 Table 4.4 Long term average monthly, seasonal and annual comparisons 32 Table 4.5 Model Fit Statistics 34 2 Table 4.6 R Fit Description 35 Table 5.1 Hydrological Disturbance Indices 41 Table A-1 Model performance at secondary sites 54 v Detention and Black Rivers Surface Water Model Hydro Tasmania Version No: FINAL 1.0 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 Detention and Black River catchments; • 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 Detention and Black Rivers Surface Water Model Hydro Tasmania Version No: FINAL 1.0 2. CATCHMENT CHARACTERISTICS The Detention catchment adjoins the north-east boundary of the Black River catchment in North West Tasmania. Both Rivers flow northwest into Bass Strait from their headwaters in the Dip Range, which rises to 554 m ASL (Detention Peak) in the south- east of both catchments. The total catchment area covered by the model is 578 km 2, which, as well as the Black and Detention Rivers, includes the significant streams of Wilsons Creek and Crayfish Creek as well as a number of smaller streams. The catchment is covered by a mix of forested areas (principally covered by sclerophyllous native forests) and agrarian plains. Some catchments, such as Wilsons Creek, are almost entirely deforested and exploited for agriculture, while others, e.g. Dip River, are forested for nearly their entire length. There are no major urban areas within the catchment (the nearby town of Stanley falls outside the catchment area). Annual rainfall varies across this catchment, mainly due to the changes in elevation and the varied exposure to the dominant westerly weather pattern. The lower catchment around the coast receives a typical annual rainfall of around 1000mm and the upper catchment around Detention Peak receives more than 1600 mm. There are 334 registered (current) entitlements for water extraction registered on the Water Information Management System (WIMS July 2007). Most of these extractions are concentrated in the lower sub-catchments and mainly relate to agriculture. The largest extraction entitlement is 500 ML, used for irrigation. Entitlements are not distributed evenly over the catchment. Extraction entitlements occur along nearly the entire length of the Black River (including, unusually, towards the upper Black River (Sc2_f, Sc2_e, Sc16_a), but excepting the middle of the catchment: see Figure 3-3), but do not occur at all along the Black River’s major tributary, the Dip River. The Wilson Creek catchment is heavily exploited for agriculture and accordingly has many extraction entitlements, while the Crayfish Creek catchment is almost entirely forested and has no water extraction entitlements. While entitlements occur in the upper part of the Detention River catchment, they are more concentrated in the lower catchment.