NAP Region Hydrological Model South Esk Catchment

Prepared By: HYDRO ELECTRIC CORPORATION ARBN 072 377 158 ABN 48 072 377 158 4 Elizabeth Street, Hobart Tasmania, Australia

Report No:118784 - Report-11 Rev. Status: Final Date Issued: 25-3-2005

NAP Region Hydrological Model

South Esk Catchment

Hydro Tasmania Page ii

DOCUMENT INFORMATION

JOB/PROJECT TITLE:

NAP Region Hydrological Models

TITLE:

South Esk Catchment

CLIENT ORGANISATION:

Department of Primary Industries, Water and Environment

CLIENT CONTACT:

Martin Read

The development of hydrological models for National Action Plan catchments and

accompanying reports have been conducted under the National Action Plan for Salinity

and Water Quality (NAPSWQ) as part of the project "Surface water hydrological models

for the NAP Region" (NAP Project 41542) and was funded by the Australian Government

and the Department of Primary Industries, Water and Environment.

DOCUMENT ID NUMBER: 118783-Report-11

DATE: 25th March 2005

REV/DRAFT NO: Draft

JOB/PROJECT MANAGER: Bryce Graham

JOB/PROJECT NUMBER: 118783

REVISION/DRAFT HISTORY:

REV DATE DESCRIPTION PREPARED REVIEWED APPROVED

0 25/3/05 Draft R. Murray B. Graham F. Ling

1 27/4/05 Final R. Murray B. Graham F. Ling

NAP Region Hydrological Models: South Esk Catchment

Hydro Tasmania 118783-Report-11 Page iii

EXECUTIVE SUMMARY

This report is part of a series of reports which present the methodologies and results from the development and calibration of hydrological models for the 13 National Action Plan (NAP) region catchments for both current and natural catchment conditions. The project is a priority action under the National Action Plan for Salinity and Water Quality (NAPSWQ). This report describes the results of the hydrological model developed for the South Esk catchment.

A model was developed for the South Esk catchment that facilitates the modeling of flow data for three scenarios:

• Scenario 1 - Natural Flow;

• Scenario 2 - Entitlements (river flows with water entitlements extracted);

• Scenario 3 - Entitlements and Environmental Flows (a scenario modeling environmental flows with all extractions included);

The results from the scenario modeling allow the calculation of indices of hydrological disturbance. These indices include:

• Hydrological Disturbance Index

• Index of Mean Annual Flow

• Index of Flow Duration Curve Difference

• Index of Seasonal Amplitude

• Index of Seasonal Periodicity

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.

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 sub-catchment summary of flows statistics, duration curves, hydrological indices and water allocation data.


Hydro Tasmania 118783-Report-11 Page 1

TABLE OF CONTENTS

EXECUTIVE SUMMARY ...................................................................... III

1 INTRODUCTION ......................................................................... 2

2 CATCHMENT CHARACTERISTICS ..................................................... 3

3 DATA COMPILATION ................................................................... 5

3.1 CLIMATE DATA (RAINFALL & EVAPORATION) ......................................................... 5 3.2 ADVANTAGES OF USING CLIMATE DRILL DATA ....................................................... 5 3.3 TRANSPOSITION OF CLIMATE DRILL DATA TO LOCAL CATCHMENT ................................ 5 3.4 STREAMFLOW DATA ..................................................................................... 6 3.5 IRRIGATION AND WATER USAGE ....................................................................... 7

4 MODEL DEVELOPMENT ............................................................... 11

4.1 SUBCATCHMENT DELINEATION ....................................................................... 11 4.2 HYDSTRA MODEL ....................................................................................... 11 4.3 AWBM ROUTINE ........................................................................................ 12 4.4 CHANNEL ROUTING .................................................................................... 14 4.5 MODEL CALIBRATIONS ................................................................................. 15 4.6 MODEL RESULTS ........................................................................................ 18 4.7 INDICES OF HYDROLOGICAL DISTURBANCE ......................................................... 18

5 REFERENCES ........................................................................... 20

LIST OF TABLES

TABLE 3.1 SUB CATCHMENT HIGH AND LOW PRIORITY ENTITLEMENTS ................................. 8 TABLE 4.1 ADOPTED CALIBRATION PARAMETERS.......................................................... 17

TABLE 4.2 MODEL FIT STATISTICS – SOUTH ESK RIVER @ PERTH ........................................ 17 TABLE 4.3 SOUTH ESK RIVER U/S TIDAL LIMIT HYDROLOGICAL DISTURBANCE INDICES .............. 19

LIST OF FIGURES FIGURE 2.1 SOUTH ESK SUB-CATCHMENT BOUNDARIES .................................................... 4

FIGURE 3.1 SOUTH ESK CLIMATE DRILL SITE LOCATIONS .................................................. 6 FIGURE 3.2 WATER ALLOCATIONS IN THE SOUTH ESK CATCHMENT .................................... 10 FIGURE 4.1 HYDSTRA SOUTH ESK MODEL SCHEMATIC .................................................... 12 FIGURE 4.2 AUSTRALIAN WATER BALANCE MODEL SCHEMATIC ......................................... 14 FIGURE 4.3 TIME SERIES COMPARISONS OF MODELED AND OBSERVED FLOW – SOUTH ESK RIVER @

PERTH - 1959 ............................................................................................ 15

FIGURE 4.4 TIME SERIES COMPARISONS OF MODELED AND OBSERVED FLOW – SOUTH ESK RIVER @ PERTH - 1977 ............................................................................................ 16

FIGURE 4.5 TIME SERIES COMPARISONS OF MODELED AND OBSERVED FLOW – SOUTH ESK RIVER @ PERTH – 2001 ............................................................................................ 16

FIGURE 4.6 COMPARISON OF DAILY MODELED AND OBSERVED FLOW – SOUTH ESK RIVER @ PERTH 17

FIGURE 4.7 SOUTH ESK RIVER @ PERTH DAILY DURATION CURVES ..................................... 18



1 INTRODUCTION

This report forms part of a larger project commissioned by the Department of Primary Industries, Water and Environment to provide hydrological models for 13 NAP region 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 South Esk catchment;

• To generate 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 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.



2 CATCHMENT CHARACTERISTICS

The South Esk River catchment is located in the north-east of Tasmania. The catchment rises in the Fingal Tier in the East and is bounded by Ben Lomond and Mt. Saddleback to the North. The South Esk River discharges into the Tamar Estuary at Launceston.

The total NAP catchment area of the South Esk River is 3,350 km2. The South Esk catchment forms part of the Tamar River Basin.

The Tamar River Basin covers 11670 square kilometres and is located in northern Tasmania. The topography of the catchment is quite varied. The major river systems consist of a floodplain, adjacent rolling hills and mountains towards the headwaters. Rainfall is quite variable ranging from as low as 510 mm at Ross in the Macquarie to 1200 mm at Gray. The estimated average annual rainfall for the major rivers in the Basin range from 600 mm to 900 mm. The catchment consists of a mixture of perennial and non-perennial streams. Major rivers such as the South Esk, Macquarie, Lake and Meander flow all year. There is a high demand on flows which has resulted in the capping of water extractions from some rivers over the period December through to April. In dry times, to protect this flow, water restrictions have become necessary, particularly in the Meander Catchment. Land use in the catchment is mainly agriculture, forestry and limited mining for coal and metals in the upper South Esk catchment. There are a growing number of properties becoming involved in irrigation for uses such as poppies and potatoes. A growing form of land use is grape growing for wine. Apart form providing water for irrigating crops and pastures, water is also used extensively for power generation. The Great Lake - South Esk power system is the largest power generating development in the State. There are a number of water resource issues in the catchment that have arisen due to intense competition for water. This competition includes that between irrigators and power generation, irrigation and town water supply and between irrigators generally (due to limited reliable water available in some areas during summer).

For modelling purposes, the South Esk catchment was sub divided into 43 sub areas. The delineation of these areas is shown in Figure 2.1. There are several historical and five current streamflow monitoring points in the catchment.

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3 DATA COMPILATION

3.1 CLIMATE DATA (RAINFALL & EVAPORATION)

Daily time-step climate data was obtained from the Queensland Department of Natural Resources & Mines (QNRM).

The Department provides time series climate drill data from 0.05o x 0.05o (about 5 km x 5 km) interpolated gridded rainfall and evaporation data based on over 6000 rainfall and evaporation stations in Australia (see www.dnr.qld.gov.au/silo) for further details of climate drill data.

3.2 ADVANTAGES OF USING CLIMATE DRILL DATA

This data has a number of benefits over other sources of rainfall data including:

• Continuous data back to 1889 (however, the further back there are less input sites available and therefore quality is reduced. The makers of the data set state that gauge numbers have been somewhat static since 1957, therefore back to 1957 distribution is considered “good” but prior to 1957 site availability may need to be checked in the study area);

• Evaporation data (along with a number of other climatic variables) is also included which can be used for the AWBM model.

3.3 TRANSPOSITION OF CLIMATE DRILL DATA TO LOCAL CATCHMENT

Ten climate drill sites were selected to give good coverage of the South Esk NAP Catchment.

Where actual long term rainfall gauge sites were available, eastings and northings for the grid data were chosen as close as possible to actual gauge site locations. This places fewer requirements on the interpolation of data. See Figure 3.1 below for locations of climate drill data sites for the South Esk catchment.



Figure 3.1 South Esk Climate Drill site locations

3.4 STREAMFLOW DATA

There are five current low gauge sites in the South Esk catchment including:

Site Name Period of Record Easting Northing

South Esk River at Perth 19/12/1956 – present 516900 5394750

South Esk River at Llewellyn 18/11/1952 – present 546850 5370340

Break O’Day River at Killymoon 04/11/1983 – present 588000 5394500

St Pauls River upstream of South Esk 04/05/1988 – present 560400 5373500

Nile River at Deddington 03/06/1982 – present 538200 5397199

The South Esk River at Perth site was used for calibration purposes, as it has a long period of record, a high quality rating, and is located near the bottom of the catchment.



3.5 IRRIGATION AND WATER USAGE

Information on the current water entitlement allocations in the catchment was obtained from DPIWE. The extractions or licenses in the catchment are of a given Surety (from 1 to 5), with Surety 1-2 representing high priority extractions for modeling purposes and Surety 3-5 representing the lowest priority. When modeling scenarios with environmental flows, water will only be available for Low Priority entitlements after environmental flow requirements have been met.

A summary table of total entitlement volumes on a daily breakdown by sub-catchment is provided below in Table 3.1 and in the NAP Catchment User Interface. A map of the water allocations in the catchment is shown in Figure 3.2.



Table 3.1 Sub Catchment High and Low Priority entitlements

Table 2. Water Entitlements Summarized - Demand (ML/d) for each Subarea & Month

Subcatchment Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec

High Priority Entitlements

SC1.01 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011

SC1.02 0 0 0 0 0 0 0 0 0 0 0 0

SC1.03 0.016 0.1 0.194 0.2 0.194 0.167 0.194 0.194 0.167 0.194 0.2 0.05

SC1.04 0 0 0 0 0 0 0 0 0 0 0 0

SC1.05 0.913 1.158 1.374 1.258 1.277 1.258 1.277 1.277 1.258 1.374 1.391 1.264

SC1.06 0 0 0 0 0 0 0 0 0 0 0 0

SC1.07 0 0 0 0 0 0 0 0 0 0 0 0

SC1.08 0 0 0 0 0 0 0 0 0 0 0 0

SC1.09 0 0 0 0 0 0 0 0 0 0 0 0

SC1.10 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011 0.011

SC1.11 0.451 0.451 0.451 0.451 0.451 0.451 0.451 0.451 0.451 0.451 0.451 0.451

SC1.12 0.407 0.407 0.407 0.407 0.407 0.407 0.407 0.407 0.407 0.407 0.407 0.407

SC1.13 0.32 0.32 0.32 0.32 0.32 0.32 0.32 0.32 0.32 0.32 0.32 0.32

SC1.14 0 0 0 0 0 0 0 0 0 0 0 0

SC2.01 0 0 0 0 0 0 0 0 0 0 0 0

SC3.01 0 0 0 0 0 0 0 0 0 0 0 0

SC4.01 0 0 0 0 0 0 0 0 0 0 0 0

SC5.01 0 0 0 0 0 0 0 0 0 0 0 0

SC5.02 0 0 0 0 0 0 0 0 0 0 0 0

SC5.03 0 0 0 0 0 0 0 0 0 0 0 0

SC6.01 0.063 0.35 0.71 0.667 0.613 0.567 0.548 0.548 0.6 0.645 0.667 0.183

SC7.01 0 0 0 0 0 0 0 0 0 0 0 0

SC8.01 0 0 0 0 0 0 0 0 0 0 0 0

SC9.01 0 0 0 0 0 0 0 0 0 0 0 0

SC10.01 0 0 0 0 0 0 0 0 0 0 0 0

SC10.02 0 0 0 0 0 0 0 0 0 0 0 0

SC10.03 0 0 0 0 0 0 0 0 0 0 0 0

SC10.04 0.016 0.016 0.016 0.016 0.016 0.016 0.016 0.016 0.016 0.016 0.016 0.016

SC10.05 0 0 0 0 0 0 0 0 0 0 0 0

SC11.01 0 0 0 0 0 0 0 0 0 0 0 0

SC12.01 0 0 0 0 0 0 0 0 0 0 0 0

SC13.01 0 0 0 0 0 0 0 0 0 0 0 0

SC14.01 0 0 0 0 0 0 0 0 0 0 0 0

SC15.01 0.014 0.014 0.014 0.014 0.014 0.014 0.014 0.014 0.014 0.014 0.014 0.014

SC16.01 0 0 0 0 0 0 0 0 0 0 0 0

SC16.02 0.448 0.448 0.448 0.448 0.448 0.448 0.448 0.448 0.448 0.448 0.448 0.448

SC17.01 0 0 0 0 0 0 0 0 0 0 0 0

SC18.01 0 0 0 0 0 0 0 0 0 0 0 0

SC19.01 0 0 0 0 0 0 0 0 0 0 0 0

SC20.01 0 0 0 0 0 0 0 0 0 0 0 0

SC20.02 0 0 0 0 0 0 0 0 0 0 0 0

SC20.03 0 0 0 0 0 0 0 0 0 0 0 0

SC21.01 0 0 0 0 0 0 0 0 0 0 0 0



Low Priority Entitlements

SC1.01 0.717 0.717 0.717 0.717 0 0 0 0 0 0 0 0.717

SC1.02 0 0 0 0 0 0 0 0 0 0 0 0

SC1.03 0 0 0 0 0 0 0 0 0 0 0 0

SC1.04 0.942 0.942 0.942 0.942 14.79 14.79 14.79 14.79 14.79 14.79 14.79 0.942

SC1.05 1.208 1.208 1.208 1.208 0.103 0.103 0.103 0.103 0.103 0.103 0.103 1.208

SC1.06 3.506 3.506 3.506 3.506 1.291 1.291 1.291 1.291 1.291 1.291 1.291 3.506

SC1.07 0 0 0 0 0 0 0 0 0 0 0 0

SC1.08 0.883 0.883 0.883 0.883 0.234 0.234 0.234 0.234 0.234 0.234 0.234 0.883

SC1.09 3.8 3.8 3.8 3.8 0.561 0.561 0.561 0.561 0.561 0.561 0.561 3.8

SC1.10 1.883 1.883 1.883 1.883 14.62 14.62 14.62 14.62 14.62 14.62 14.62 1.883

SC1.11 5.871 5.871 5.871 5.871 5.43 5.43 5.43 5.43 5.43 9.075 5.43 5.871

SC1.12 15.71 15.71 15.71 15.71 19.8 19.8 19.8 19.8 19.8 19.8 19.8 15.71

SC1.13 3.258 3.258 3.258 3.258 0.28 0.28 0.28 0.28 0.28 0.28 0.28 3.258

SC1.14 1.397 1.397 1.397 1.397 0.122 0.122 0.122 0.122 0.122 0.122 0.122 2.755

SC2.01 0 0 0 0 0 0 0 0 0 0 0 0

SC3.01 1.167 1.167 1.167 1.167 0 0 0 0 0 0 0 1.167

SC4.01 0.942 0.942 0.942 0.942 0.005 0.005 0.005 0.005 0.005 0.005 0.005 0.942

SC5.01 0 0 0 0 1.93 1.93 1.93 1.93 1.93 1.93 1.93 0

SC5.02 0 0 0 0 0.037 0.037 0.037 0.037 0.037 0.037 0.037 0

SC5.03 0.437 0.437 0.437 0.437 2.76 2.76 2.76 2.76 2.76 2.76 2.76 0.437

SC6.01 0.117 0.117 0.117 0.117 0 0 0 0 0 0 0 0.117

SC7.01 0 0 0 0 0 0 0 0 0 0 0 0

SC8.01 0.942 0.942 0.942 0.942 0 0 0 0 0 0 0 0.942

SC9.01 0.942 0.942 0.942 0.942 0 0 0 0 0 0 0 0.942

SC10.01 0 0 0 0 0 0 0 0 0 0 0 0

SC10.02 0 0 0 0 0 0 0 0 0 0 0 0

SC10.03 0.375 0.375 0.375 0.375 1.953 1.953 1.953 1.953 1.953 1.659 1.659 0.375

SC10.04 0 0 0 0 0.262 0.262 0.262 0.262 0.262 0.262 0.262 0

SC10.05 1.472 1.472 1.472 1.472 0.538 0.538 0.538 0.538 0.538 0.538 0.538 1.472

SC11.01 0 0 0 0 0 0 0 0 0 0 0 0

SC12.01 0 0 0 0 0 0 0 0 0 0 0 0

SC13.01 0.317 0.317 0.317 0.317 0 0 0 0 0 0 0 0.317

SC14.01 0 0 0 0 0 0 0 0 0 0 0 0

SC15.01 0 0 0 0 0.093 0.093 0.093 0.093 0.093 0.093 0.093 0

SC16.01 0 0 0 0 0 0 0 0 0 0 0 0

SC16.02 2.825 2.825 2.825 2.825 0 0 0 0 0 0 0 2.825

SC17.01 0 0 0 0 0 0 0 0 0 0 0 0

SC18.01 0 0 0 0 1.178 1.178 1.178 1.178 1.178 1.178 1.178 0

SC19.01 1.947 1.947 1.947 1.947 11.19 11.19 11.19 11.19 11.19 11.19 11.19 1.947

SC20.01 0 0 0 0 0.421 0.421 0.421 0.421 0.421 0.421 0.421 0

SC20.02 13.28 13.28 13.28 13.28 13.9 13.9 13.9 13.9 13.9 13.9 13.9 13.28

SC20.03 0 0 0 0 0 0 0 0 0 0 0 0

SC21.01 0 0 0 0 2.734 2.734 2.734 2.734 2.734 2.734 2.734 0



Figure 3.2 Water allocations in the South Esk catchment



4 MODEL DEVELOPMENT

4.1 SUBCATCHMENT DELINEATION

Subcatchment delineation was performed using CatchmentSIM GIS software.

CatchmentSIM is a freely available 3D-GIS topographic parameterisation and hydrologic analysis model. The model automatically delineates watershed and subcatchment boundaries, generalises geophysical parameters and provides in-depth analysis tools to examine and compare the hydrologic properties of subcatchments. The model also includes a flexible result export macro language to allow users to fully couple CatchmentSIM with any hydrologic modelling package that is based on subcatchment networks.

The software is tailored towards full coupling with third party hydrologic models by:

• Firstly, CatchmentSIM is used to delineate a catchment, break it up into numerous subcatchments, determine their areas and spatial topographic attributes and analyse each subcatchment's hydrologic characteristics to provide insight into the rainfall response of various catchments and resultant assignment of hydrologic modelling parameters.

• Following this, the derived subcatchments and their attributes may be directly imported into any third party hydrologic model. This is achieved by a flexible result export macro language with specifically developed macro scripts enabling automatic development on input files (text or binary) for other models.

CatchmentSIM can be thought of as a collection of topographic and hydrologic analysis algorithms that have been purpose built for the process of hydrologic analysis and included in a Windows based user-friendly GIS environment. The program has not been intended to be a 'black box' application and as such, all algorithms are described from a conceptual perspective in the user manual.

For more detailed information on CatchmentSIM see the CatchmentSIM Homepage www.toolkit.net.au/catchsim/

4.2 HYDSTRA MODEL

A computer simulation model was developed using Hydstra Modelling. The South Esk sub-catchments, described in Figure 2.1, were represented by model “nodes” and connected together by “links”. A schematic of this model is displayed in Figure 4.1.

The rainfall and evaporation is calculated for each subcatchment using inverse-distance gauge weighting. The gauge weights were automatically calculated at the start of each model run. The weighting is computed for the centroid of the subcatchment. A quadrant system is drawn, centred on the centroid. A weight for the closest gauge in each quadrant is computed as the inverse, squared, distance between the gauge and centroid. For each time step and each node, the gauge weights are applied to the incoming rainfall and evaporation data.

The AWBM Two Tap rainfall/runoff model was used to calculate the runoff for each subcatchment separately. This was chosen over the usual method of a single AWBM model for the whole catchment as it more accurately distributes the runoff and base flow spatially over the catchment.

The flow in each sub-catchment is routed through the catchment via a channel routing function.



Figure 4.1 Hydstra South Esk Model schematic

4.3 AWBM ROUTINE

The AWBM Two Tap model is a relatively simple water balance model with the following characteristics:

• it has few parameters to fit;

• the model representation is easily understood in terms of the actual outflow hydrograph;

• the parameters of the model can largely be determined by analysis of the outflow hydrograph;

• the model accounts for partial area rainfall-run-off effects;

• run-off volume is insensitive to the model parameters.

For these reasons parameters can more easily be transferred to ungauged catchments.



The AWBM routine used in this study is the Boughton Revised AWBM model (Boughton, 2003), which reduces the three partial areas and three surface storage capacities to relationships based on an average surface storage capacity.

Boughton & Chiew (2003) have shown that when using the AWBM model, the total amount of runoff is mainly affected by the average surface storage capacity and much less by how that average is spread among the three surface capacities and their partial areas. Given an average surface storage capacity (Ave), the three partial areas and the three surface storage capacities are found by;

Partial area of smallest store A1=0.134



Capacity of smallest store C1=(0.01*Ave/A1)=0.075*Ave

Capacity of smallest store C2=(0.33*Ave/ A2)=0.762*Ave

Capacity of smallest store C3=(0.66*Ave/ A3)=1.524*Ave

The AWBM routine produces two outputs; direct run-off and base-flow. Direct run-off is produced after the content of any of the soil stores is exceeded; it can be applied to the stream network directly or by catchment routing across each subcatchment. Base-flow is usually supplied unrouted directly to the stream network, at a rate proportional to the water depth in the ground water store. The ground water store is recharged from a proportion of excess rainfall from the three surface soil storages.

The AWBM processes are shown below in Figure 4.2;



Figure 4.2 Australian Water Balance Model Schematic

4.4 CHANNEL ROUTING

A common method employed in nonlinear routing models is a power function storage relation. S = K.Qn

K is a dimensional empirical coefficient, the reach lag (time). In the case of Hydstra/TSM Modelling:

α and

Li = Channel length (km)

α = Channel Lag Parameter n = Non-linearity Parameter Q = Outflow from Channel Reach (m3/s)



A reach length factor may be used in the declaration of α to account for varying reach lag for

individual channel reaches. eg. α.fl where fl is a length factor. Parameters required by Hydstra/TSM Modelling and their legal bounds are:

α Channel Lag Parameter Between 0.0 and 5.0

L Channel Length (km) Greater than 0.0 (km)

n Non-linearity Parameter Between 0.0 and 1.0

4.5 MODEL CALIBRATIONS

Calibration was achieved by adjusting catchment parameters so that the modeled data replicated the record at the South Esk River @ Perth site (1957 – 2005).

The results of calibration are shown in Figure 4.3, 4.4 and 4.5 below. Overall the model gives a passable representation of the flows in the South Esk River. Given the uncertainties in the “naturalness” of the gauged data, this was as good an estimate of daily flows as could be expected and it is unlikely that a better fit could have been achieved using other calibration tools.

Figure 4.3 Time Series Comparisons of Modeled and Observed Flow – South Esk River at Perth - 1959

1959 19600

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

22000

24000

Period(01/01/1959 @ 00:00:00 to 01/01/1960 @ 00:00:00)

181.1/100.00/1: SOUTH ESK [AT PERTH] (PTo(140.00,0);PTo(140.02,0);Aggregate(Daily)) - Flow (Ml/day)P:\Project\Projects\111xxx\1112xx\111253 RA Irrigation Projects\FarmDamsImpacts\TS_Model\SEskPerthMod.tsf



Figure 4.4 Time Series Comparisons of Modeled and Observed Flow – South Esk River at Perth - 1977

1977 19780

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

Period(01/01/1977 @ 00:00:00 to 01/01/1978 @ 00:00:00)


Figure 4.5 Time Series Comparisons of Modeled and Observed Flow – South Esk River at Perth – 2001

2001 20020

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

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Period(01/01/2001 @ 00:00:00 to 01/01/2002 @ 00:00:00)




Table 4.1 Adopted calibration parameters

Parameter Value Parameter Value

Alpha 3 K2 0.95

N 0.8 GWStoreSat 30

INFbase 0.50 GWStoreMax 40

CapAve 72.7 H_GW 30

K1 0.97 EvapScale 1

Table 4.2 Model Fit Statistics – South Esk River at Perth

Measure of Fit Value Daily coefficient of determination (R2 value) 0.66

Monthly coefficient of determination (R2 value) 0.85 Difference in observed and estimated average flows +10.6 %

Figure 4.6 Comparison of Daily Modeled and Observed Flow – South Esk River at Perth

South Esk River @ Perth

R2 = 0.655

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4.6 MODEL RESULTS

Three scenarios were modeled for the current project, they were:

• Scenario 1 - Natural Flow

• Scenario 2 - Entitlements (river flows with water entitlements extracted)

• Scenario 3 - Entitlements and Environmental Flows (a scenario modeling environmental flows with all extractions included)

For each of the three scenarios, daily flow data sequences were generated for the South Esk River at Perth.

Outputs of daily flow sequence, daily flow duration curves, and indices of hydrological disturbance are presented below.

Figure 4.7 South Esk River at Perth Daily Duration Curves

0.10

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0% 10% 20% 30% 40% 50% 60% 70% 80% 90% 100%

Percent Of Tim e Exceeded

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4.7 INDICES OF HYDROLOGICAL DISTURBANCE

The calculation of the estimates of natural flows and current flows (farm dams and irrigation) were used to calculate indices of hydrological disturbance. These indices include:

• Hydrological Disturbance Index

• Index of Mean Annual Flow

• Index of Flow Duration Curve Difference

• Index of Seasonal Amplitude

• Index of Seasonal Periodicity

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.



Table 4.3 South Esk River at Perth Hydrological Disturbance Indices

Disturbance Indice South Esk R. @ Pert

Hydrological Disturbance Index 0.47

Index of Mean Annual Flow 0.44

Index of Flow Duration Curve Difference 0.31

Index of Seasonal Periodicity 0.92

Index of Seasonal Amplitude 0.42

Hydrological Disturbance Index: This provides an indication of the hydrological disturbance to the river’s natural flow regime. A value of 1 represents no hydrological disturbance, while a value approaching 0 represents extreme hydrological disturbance.

Index of Mean Annual Flow: This provides a measure of the difference in total flow volume between current and natural conditions. It is calculated as the ratio of the current and natural mean annual flow volumes and assumes that increases and reductions in mean annual flow have equivalent impacts on habitat condition.

Index of Flow Duration Curve Difference: The difference from 1 of the proportional flow deviation, averaged over p monthly flow percentile point. A measure of the overall difference between current and natural monthly flow duration curves. All flow diverted would give a score of 0.

Index of Seasonal Periodicity: The change in seasonal timing of flows. It is defined as the difference from 1 of one twelfth of the sum of the absolute values of the differences between current and natural of first, the numerical values of the months with the highest mean monthly flows, and second, the numerical values of the months with the lowest mean monthly flows.

Index of Seasonal Amplitude: The change in amplitude of the seasonal pattern of monthly flows. It is defined as the average of two current: natural ratios, firstly, that of the highest monthly flows, and secondly, that of the lowest monthly flows based on calendar month means.



5 REFERENCES

Boughton, W.C. and Chiew, F.,(2003) Calibrations of the AWBM for use on Ungauged Catchments

CatchmentSIM Homepage www.toolkit.net.au/catchsim/ January 2005.

SKM (2003) Estimating Available Water in Catchments in Catchments Using Sustainable Diversion Limits. Farm Dam Surface Area and Volume relationship, report to DSE, Draft B October 2003

Hydrology Theme Summary of Pilot Audit Technical Report – Sustainable Rivers Audit. MDBC Publication 08/04.

National Land and Water Resources Audit (NLWRA) www.audit.ea.gov.au/anra/water/; January 2005.

Documents

NAP Region Hydrological Model South Esk Catchment