HAWKESBURY NEPEAN SALINE DYNAMICS MODEL CALIBRATION

by

D R Cox, W L Peirson and J L Davies

Technical Report 2003/01 March 2003 THE UNIVERSITY OF SCHOOL OF CIVIL AND ENVIRONMENTAL ENGINEERING WATER RESEARCH LABORATORY

HAWKESBURY NEPEAN ESTUARY SALINE DYNAMICS MODEL CALIBRATION

WRL Technical Report 2003/01 March 2003

by

D R Cox, W L Peirson and J L Davies

https://doi.org/10.4225/53/58d4a604e8ea6 Water Research Laboratory School of Civil and Environmental Engineering Technical Report No 2003/01 University of New South Wales ABN 57 195 873 179 Report Status Final King Street Date of Issue March 2003 Manly Vale NSW 2093

Telephone: +61 (2) 9949 4488 WRL Project No. 02107 Facsimile: +61 (2) 9949 4188 Project Manager D R Cox

Title Hawkesbury Nepean Saline Dynamics – Model Calibration

Author(s) D R Cox, W L Peirson and J L Davies

Client Name Hawkesbury Management Forum

Client Address PO Box 556, Windsor NSW 2756

Client Contact Brian Walters

Client Reference

The work reported herein was carried out at the Water Research Laboratory, School of Civil and Environmental Engineering, University of New South Wales, acting on behalf of the client.

Information published in this report is available for general release only with permission of the Director, Water Research Laboratory, and the client. WRL TECHNICAL REPORT 2003/01

CONTENTS

1. INTRODUCTION 1 2. BACKGROUND 2 2.1 Environmental Flows 2 2.2 The Hawkesbury Nepean River 2 2.2.1 General Characteristics 2 2.2.2 Modifications to the Natural Flow Regime 3 3. NUMERICAL MODELLING 4 3.1 Estuary Model Description 4 3.2 Hydrodynamic Model Calibration 4 3.3 Salinity Model Calibration 7 4. CONCLUSIONS 10 5. REFERENCES 11

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LIST OF TABLES

1. Summary of Tide Level and Discharge Calibration Data 2. Comparison of Measured and Modelled Tidal Prisms, 30 April 1981 3. Comparison of Measured and Modelled Tidal Prisms, 29 May 1981 4. Comparison of Measured and Modelled Tidal Prisms, 26 June 1981 5. Comparison of Measured and Modelled Tidal Prisms, 20 August 1981

LIST OF FIGURES

1. Hawkesbury Nepean River System 2. Hawkesbury Nepean Estuary Model Mesh 3. Location of Tidal Calibration Data 4. Comparison of Measured and Modelled Tide Levels, 30 April 1981 5. Comparison of Measured and Modelled Tide Levels, 29 May 1981 6. Comparison of Measured and Modelled Tide Levels, 26 June 1981 7. Comparison of Measured and Modelled Tide Levels, 20 August 1981 8. Comparison of Measured and Modelled Tidal Lags, 30 April 1981 9. Comparison of Measured and Modelled Tidal Lags, 29 May 1981 10. Comparison of Measured and Modelled Tidal Lags, 26 June 1981 11. Comparison of Measured and Modelled Tidal Lags, 20 August 1981 12. Major River Inflows to Hawkesbury Nepean, February 1977 – January 1978 13. Comparison of Measured and Modelled Depth Averaged Salinity, Feb 1977 – Jan 1978

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1. INTRODUCTION

The University of New South Wales, Water Research Laboratory (WRL) was commissioned by the Hawkesbury Nepean River Management Forum to establish a model of the estuary which was suitable for long term studies of salinity, environmental flows, water quality and associated ecological impacts.

This report describes the development of the model and its calibration against measured tide levels, tidal discharges and longitudinal salinity structure in the Hawkesbury Nepean estuary. The one dimensional hydrodynamic and water quality model extends from West Head, at the junction of the Hawkesbury Nepean with and , to the upstream tidal limit at Yarramundi. Tide level and tidal flow data obtained by MHL (1988) during four one-day gauging exercises on the during 1981 were used to calibrate the hydrodynamic model. The salinity model was calibrated against depth- averaged salinities obtained along the length of the Hawkesbury River by the Electricity Commission at approximately 2 weekly intervals between February 1977 and January 1978.

WRL TECHNICAL REPORT 2003/01 2.

2. BACKGROUND

2.1 Environmental Flows

Many in Australia are subject to irregular and non-seasonal rainfall patterns, in which long periods of low rainfall may be followed by significant rainfall events at varying intervals. As a result, the natural estuarine salinity structure may also be highly variable. During periods of high rainfall, salt water is flushed from the estuary by the increased freshwater flow, while during periods of low rainfall, saline water from the estuary mouth is able to penetrate further up the estuary, either as a density current or through tidal mixing (Dyer, 1997).

Human activities have greatly modified the freshwater flow regime in many Australian . Any flow storage or diversion structure that alters the amount of freshwater flow to a river system may influence the health of downstream aquatic ecosystems. Examples of anthropogenic influences on river flows include the construction of and weirs, withdrawal of water for household use, irrigation or industry, sewage treatment plant discharges, changes to the river channel and catchment modifications affecting runoff (such as land clearing and introduction of impervious surfaces such as roads, rooves and paving). These activities may cause persistent changes to the natural salinity structure of an estuary and consequently have implications for the health of aquatic ecosystems.

Consideration of the ecological impacts of reduced river flows due to human water usage has led to the concept of “Environmental Flows”. The term “Environmental Flows” describes freshwater flow (typically instream flow) that is maintained solely for environmental reasons, to maintain the health and biodiversity of a particular water-related entity, such as a river or estuary (Peirson et al., 2001, 2002). Environmental flows are essential to the minimisation of negative influences on the health of aquatic ecosystems resulting from human alterations to the flow regime.

2.2 The Hawkesbury Nepean River

2.2.1 General Characteristics

The Hawkesbury Nepean estuary (Figure 1) is an example of a tide-dominated, drowned estuary (Roy et al., 2001). The river is approximately 300km long and supplies 98% of ’s potable water supply. The limit of saline intrusion (> 0.5 ppt) in the estuary is

WRL TECHNICAL REPORT 2003/01 3. usually in the vicinity of the junction but may move as far upstream as Sackville (SPCC, 1983).

2.2.2 Modifications to the Natural Flow Regime

The freshwater flow and hydraulic characteristics of the Hawkesbury Nepean River have been heavily modified by the construction of dams, weirs and other water supply structures in the upper parts of the catchment, and to a lesser extent, the use of water for irrigation and returns to the river from sewage treatment plants. Dams and other major water supply structures impacting on flows in the Hawkesbury-Nepean include:

• The (a system of weirs, canals, tunnels and aqueducts constructed from the 1860s onwards to divert flows from the Upper Nepean to Sydney, with storage in following its completion in 1888) • Cataract (completed 1907) • (1926) • (1927) • (1935) • (1960) • Six dams constructed between 1907 and 1942 on tributaries of the , including Lake Medlow, Greaves Creek Dam, the Upper, Middle and Lower Cascade Dams, and Woodford Dam. These dams now serve only the middle and upper reaches of the Blue Mountains, from Faulconbridge to Mt. Victoria.

The (completed in 1977) allows transfer of water from the to the Wingecarribee Reservoir during times of drought, which can then be directed to either or Nepean Dam. Water can also be supplied to the from Avon Dam and Nepean Dam.

Water is extracted for irrigation purposes at numerous locations, the largest volumes of which are taken from the river between the Grose River and Colo River junctions.

WRL TECHNICAL REPORT 2003/01 4.

3. NUMERICAL MODELLING

3.1 Estuary Model Description

The hydrodynamics and salinity distribution in the Hawkesbury Nepean estuary have been simulated using RMA-2 and RMA-11, both components of the RMA finite element modelling suite. A similar approach was applied to that previously used for salinity studies of the by Peirson et al. (1999).

Both RMA-2 and RMA-11 were configured using the same one-dimensional mesh, which extends upstream to the tidal limit at Yarramundi, just upstream of the of the Grose and Nepean Rivers (Figure 2). The mesh includes the tidal sections of the other major tributaries of the Hawkesbury River downstream of this point, namely the Colo River, Macdonald River, Mangrove Creek, , , Mullet Creek and . At its downstream end, the mesh extends to a line between the eastern sides of Middle Head and West Head, at the junction of the Hawkesbury Nepean estuary with Brisbane Water and Pittwater.

3.2 Hydrodynamic Model Calibration

Tidal currents and freshwater inflows to the Hawkesbury Nepean estuary were simulated using the hydrodynamic model RMA-2 (King, 1998). An ocean tidal boundary condition was applied at the downstream end of the model and the major freshwater inflows to the system. Streamflow data for the Nepean River at Penrith, the Colo River and Macdonald River were used to define the freshwater inflow at the upstream limits of the model. Gauged flow data was not available for the Grose River for the period of the hydrodynamic model calibration, and HSPF modelled catchment flows from a study by SMEC (2002a, b) were used to define the freshwater input from this source. It would not be expected that smaller sources of freshwater inflow would have much impact on the tidal calibration.

Tide level and tidal flow data obtained by MHL (1988) during four one-day gauging exercises on the Hawkesbury River, between April and August 1981, were used to calibrate the hydrodynamic model. Each exercise concentrated on a particular section of the river, and included current metering on a number of lines across the river and monitoring of tide levels throughout a tidal cycle. The data used for the hydrodynamic model calibration are summarised in Table 1, and the locations of the tide gauges and discharge metering lines are shown on Figure 3. Tideboards located adjacent to a flow metering line have the same number as that line. The model was calibrated by varying the roughness along the tidal

WRL TECHNICAL REPORT 2003/01 5. channel and, as a result of the calibration process, a constant Manning’s n value of 0.025 was adopted throughout the model.

Table 1 Summary of Tide Level and Discharge Calibration Data

Date/ Locality Locations Tide Gauges Flow Metering Lines 30 April 1981 Liverpool Reach TB1 Line 1 Windsor Clarence Reach TB2 Line 2 Wilberforce Reach TB3 Line 3 Windsor Reach TB4 Line 4 Lower Portland TB5 Sackville Reach TB16 29 May 1981 Lower Portland TB5 Trollope Reach TB6 Line 6 Bathurst Creek TB7 Line 7 Macdonald River TB8 Line 8 26 June 1981 Lower Portland TB5 Spencer Big Jims Point TB9 Line 9 Couranga Point TB10 Line 10 Mangrove Creek TB11 Line 11 20 August 1981 TB12 Line 12, 12.1 Mooney Creek Mooney Mooney Creek TB13 Line 13 Mooney Mooney Point TB13.1

Comparisons of the measured and modelled high and low water levels along the Hawkesbury River for the four data collection exercises are shown in Figures 4 to 7. Comparisons of the measured and modelled tidal lags in the estuary are shown in Figures 8 to 11.

The model results show good agreement with the tidal levels and lags at the gauging sites in both the Mooney Creek and Spencer localities which were surveyed on 20 August and 26 June respectively (Figures 6, 7, 10 and 11). In this region less than 40 km upstream of West Head, the tidal lags are less than 15 minutes and differences between the measured and modelled tide levels less than 0.05m. Between Wisemans Ferry and the Colo River junction there is good agreement between the measured and modelled low tide level and low tide lag, but the modelled high tide is 0.1 to 0.2m higher and occurs between 30 and 45 minutes earlier than measured (Figures 4, 5, 8 and 9).

WRL TECHNICAL REPORT 2003/01 6.

Between the Colo junction and Windsor, the tidal range is correctly reproduced by the model, but both the modelled high and low tide levels are between 0.1 and 0.2m above the measured tide levels (Figure 4). It is possible that this particular discrepancy could be indicative of a survey datum error. The modelled low tide occurs between 30 and 45 minutes earlier than measured and for the stations between Little Cattai Creek and Windsor, high tide occurs up to 1 hour later than measured.

The measured and modelled tidal prisms at the flow gauging lines are listed in Tables 2 to 5. At most locations along the Hawkesbury River channel the discrepancy between the measured and modelled tidal prisms was less than 10%.

The discrepancy is slightly higher (12%) at Line 12, upstream of the Brooklyn Bridge. Line 3, downstream of Windsor was problematic with modelled tidal prisms were too high by about 50% on the ebb tide and 30% on the flood. It is noted that the tidal flows here are relatively small and much better results were obtained at the lines immediately upstream and downstream. The tidal prisms for the Macdonald River, Mangrove Creek and Mooney Mooney Creek appear to be underestimated by up to 60%, but these flows are small in comparison to those in the main Hawkesbury channel and are unlikely to have much impact on the saline dynamics.

Table 2 Comparison of Measured and Modelled Tidal Prisms, Windsor, 30 April 1981

Line 1 Line 2 Line 3 Line 4 Tidal Prism Model Proto. Model Proto. Model Proto. Model Proto. (m3 x 106) Ebb 12.81 12.54 3.54 3.29 1.91 1.26 1.66 0.99 Flood 9.05 9.21 2.41 2.33 1.20 0.91 1.01 0.61

Table 3

Comparison of Measured and Modelled Tidal Prisms, Wisemans Ferry, 29 May 1981

Line 6 Line 7 Line 8 Tidal Prism Model Proto. Model Proto. Model Proto. (m3 x 106) Ebb 16.05 16.24 13.27 15.37 0.53 1.21 Flood 13.02 14.24 11.52 13.67 0.32 0.70

WRL TECHNICAL REPORT 2003/01 7.

Table 4 Comparison of Measured and Modelled Tidal Prisms, Spencer, 26 June 1981

Line 9 Line 10 Line 11 Tidal Prism Model Proto. Model Proto. Model Proto. (m3 x 106) Ebb 27.30 29.90 20.06 26.22 1.34 1.97 Flood 30.46 29.05 24.50 23.20 1.33 2.55

Table 5 Comparison of Measured and Modelled Tidal Prisms, Mooney Creek, 20 August 1981

Line 12 + 12.1 Line 13 Tidal Prism Model Proto. Model Proto. (m3 x 106) Ebb 48.56 55.47 3.99 7.04 Flood 49.32 56.00 4.45 7.27

Based on the data presented, the hydrodynamic model is sufficiently calibrated as a basis for the salinity model.

3.3 Salinity Model Calibration

The horizontal salinity distribution in the Hawkesbury Nepean estuary was simulated using the water quality model RMA-11 (King, 1997). The salinity model was calibrated against depth-averaged salinities obtained along the length of the Hawkesbury River by the Electricity Commission at approximately 2 weekly intervals between February 1977 and January 1978. As described in Dyson and Druery (1985) and PWD (1987), the Elcom salinity data has been corrected to correspond to the time of high water slack.

Both the hydrodynamic and salinity models were run for the period from 1 January 1977 to 31 January 1978, to allow for a one month startup period. As before, the hydrodynamic model was run with freshwater inflows and a downstream (ocean) tidal boundary condition. Output from the hydrodynamic model was used to provide the water levels and flow within the estuary for input to the salinity model. In RMA-11, the salinity of tidal inflows at the downstream boundary of the model was assumed to be 35 ppt while the salinity of freshwater inflows was assumed to be 0 ppt.

WRL TECHNICAL REPORT 2003/01 8.

Simulations were undertaken using both a half-hourly and an hourly time step, in order to determine the most suitable time step for the purposes of proposed longer term salinity simulations (10-100 years). These long term simulations would be expected to be quite demanding in terms of computer time, and an hourly time step would be expected to be the maximum possible time step to allow adequate resolution of tidal variations in water level, currents and salinity.

Measured daily freshwater inflows were available for January 1977 - January 1978 for the Nepean River at Yarramundi, Grose River, Colo River and Macdonald River (Figure12). Gaps in the flow record for the Grose River were filled using catchment flows from the HSPF model. The HSPF modelled rainfall runoff and STP flows for the catchments of Redbank Creek, Rickabys Creek, South Creek, Eastern Creek, Cattai Creek, Berowra Creek and Calna Creek were also included in the model, as were the major irrigation extractions from South Creek, and the Hawkesbury River near Windsor and Cattai Creek.

A varying diffusion coefficient was used in the model to account for the changing geometry and tidal flushing of the system. Following Elder (1959), we have used a diffusion coefficient, D, of the form:

D = αU max,tidal h

where Umax, tidal is the maximum tidal velocity occurring in a given reach, h is the mean hydraulic depth and α is a coefficient.

The salinity model was calibrated by varying the diffusion parameter, α, as defined above. A value of α = 10 was adopted, with an overriding minimum value of the of the diffusion coefficient, D = 10 m2/s at the upstream end of the model. The diffusion in the downstream parts of the estuary was further increased to 200 m2/s to allow for the effects of salinity stratification on the depth averaged salinity. These values are consistent with the diffusion coefficients calculated directly from the Elcom salinity data by Dyson and Druery (1985).

A comparison of the measured and modelled depth averaged salinities is presented in Figure 13, showing the locations of the 1 ppt, 5 ppt, 10 ppt and 20 ppt isohalines over the simulation period. The results are presented for simulations undertaken using both a half hourly and an hourly model time step.

The salinity modelling results show the effects of both tidal flows and variations in the freshwater inflow to the Hawkesbury River estuary. During a tidal cycle, the location of a

WRL TECHNICAL REPORT 2003/01 9. particular salinity level may move up to 8km along the river channel. The measured salinities are high water salinities and should therefore be compared with the upper location limit of the model results in each case.

The model results generally show good agreement with the data, with the maximum discrepancy in the location of the 1ppt isohaline during November 1977 – January 1978, towards the end of a long relatively dry period. The model overestimated the 1ppt intrusion into the upper sections of the tidal estuary. This is most likely due to some small inflows that were not included in the modelling.

WRL TECHNICAL REPORT 2003/01 10.

4. CONCLUSIONS

A calibrated hydrodynamic and salinity model has been developed for the Hawkesbury Nepean estuary, which is suitable for long-term simulations of environmental flows. A one- dimensional mesh has been established, extending from West Head at the junction of the Hawkesbury Nepean estuary with Brisbane Water and Pittwater, to the upstream tidal limit at Yarramundi. The model has been calibrated against measured tide level, flow discharges and salinity data from the estuary.

The model results show good agreement with the tidal levels and lags at the gauging sites less than 50km from the ocean, near Mooney Mooney Creek and Spencer. In this region, the tidal lags were less than 15 minutes and differences between the measured and modelled tide levels were less than 0.05m. The maximum discrepancy between measured and modelled tides was at the most upstream tidal gauging site, near Windsor, where the discrepancy in high or low tide elevation was up to 0.2m and the discrepancy in tidal lag was up to 1 hour. It is however noted that the tidal range near Windsor was correctly predicted by the model and it is possible there may be a survey error affecting both measured high and low tide levels in this area.

At most locations along the Hawkesbury River channel the discrepancy between the measured and modelled tidal prisms was less than 10%.

The salinity modelling results show good agreement with the data and indicate that the model is calibrated for the purposes of salinity modelling. The results show the effects of both tidal flows and variations in the freshwater inflow to the Hawkesbury River estuary. The maximum discrepancy was in the location of the 1ppt isohaline during the period from November 1977 to January 1978, which was towards the end of a long relatively dry period and may be due to small freshwater inflows which were not included in the model.

WRL TECHNICAL REPORT 2003/01 11.

5. REFERENCES

Dyer, K.B. (1997) “Estuaries: A Physical Introduction”, 2nd Edition, John Wiley & Sons.

Dyson A.R. and Druery B.M. (1985) “The impact of sand extraction on salt intrusion in the Hawkesbury River”, 1985 Australasian Conference on Coastal and Ocean Engineering, Christchurch, New Zealand.

Elder, J.W. (1959) “The dispersion of marked fluid in turbulent shear flow”, J. Fluid Mech., 5, 554-560.

King, I.P. (1997) “RMA-11 – A Three Dimensional Finite Element Model for Water Quality in Estuaries and Streams, Version 2.5”, Department of Civil Engineering, University of California, Davis.

King, I.P. (1998) “RMA-2 – A Two Dimensional Finite Element Model for Flow in Estuaries and Streams, Version 6.5”, Department of Civil Engineering, University of California, Davis.

MHL (1988) “Hawkesbury River Tidal Data 1981”, NSW Public Works Department, Manly Hydraulics Laboratory, Report No 369 (Volumes 1 and 2), PWD Report No 88002.

Peirson, W.L., Bishop, K.A., Nittim, R. and Chadwick, M.J. (1999) “An investigation of the potential ecological impacts of freshwater extraction from the Richmond River tidal pool”, Water Research Laboratory, University of NSW, Technical Report 99/51.

Peirson, W.L., Nittim, R., Chadwick, M.J., Bishop, K.A. and Horton, P.R. (2001) “Assessment of changes to saltwater/freshwater habitat from reductions in flow to the Richmond River estuary, Australia”, Water Science & Technology, 43(9), 89-97.

Peirson, WL., Bishop, K., Van Senden, D., Horton, PR. and Adamantidis, CA. (2002) “Environmental Water Requirements to Maintain Estuarine Processes”, Water Research Laboratory, University of NSW, Technical Report No. 00/11, also published as Environmental Flows Initiative Technical Report Number 3, Commonwealth of Australia, Canberra.

PWD (1987) “Hawkesbury River hydraulic and sediment transport processes, Report No. 1: Tidal data compilation”, NSW Public Works Department Report No. PWD87058.

WRL TECHNICAL REPORT 2003/01 12.

Roy, P.S., Williams, R.J., Jones, A.R., Yassini, I., Gibbs, P.J., Coates, B., West, R.J., Scanes, P.R., Hudson, J.P. and Nichol, S. (2001) “Structure and function of south-east Australian estuaries”, Estuarine, Coastal and Shelf Science, 53, 351-384.

SMEC (2002a) “Hydrologic Data Compilation Summary Report”, SMEC Australia Pty Ltd report to Hawkesbury Nepean River Expert Panel.

SMEC (2002b) “Assessment of the Change in Hydrological Regime in the Hawkesbury Nepean River”, SMEC Australia Pty Ltd report to Hawkesbury Nepean Expert Panel.

SPCC (1983) “Water Quality in the Hawkesbury-Nepean River: A Study and Recommendations”, State Pollution Control Commission Report, September 1983.

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Figure WRL HAWKESBURY NEPEAN RIVER SYSTEM 1

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Figure WRL HAWKESBURY NEPEAN ESTUARY MODEL MESH 2

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Figure WRL LOCATION OF TIDAL CALIBRATION DATA 3

Report No. 2003/01 02107-03.cdr Measured Modelled RMA Chainage (m) 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2

Level, AHD (m) AHD Level, r Wate

Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LEVELS, 30 APRIL 1981 4 Report No. 2003/01

Measured Modelled RMA Chainage (m) RMA Chainage 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2

Level, AHD (m) AHD Level, r Wate

Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LEVELS, 29 MAY 1981 5 Report No. 2003/01

Measured Modelled RMA Chainage (m) RMA Chainage 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2

Level, AHD (m) AHD Level, r Wate

Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LEVELS, 26 JUNE 1981 6 Report No. 2003/01

Measured Modelled RMA Chainage (m) RMA Chainage 0 10000 20000 30000 40000 50000 60000 70000 80000 90000 100000 110000 120000 130000

1.2 1.0 0.8 0.6 0.4 0.2 0.0 -0.2 -0.4 -0.6 -0.8 -1.0 -1.2

Level, AHD (m) AHD Level, r Wate

Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LEVELS, 20 AUGUST 1981 7 Report No. 2003/01

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Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LAGS 8

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Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LAGS 9

29 MAY 1981 Report No. 2003/01 fig9.doc

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Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LAGS 10

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Figure WRL COMPARISON OF MEASURED AND MODELLED TIDE LAGS 11

20 AUGUST 1981 Report No. 2003/01 fig11.doc

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Figure WRL MAJOR RIVER INFLOWS TO HAWKESBURY NEPEAN 12

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a) Time Step = 0.5 hour 130000 Modelled - 1ppt 120000 Modelled - 5ppt Modelled - 10ppt 110000 Modelled - 20ppt Measured - 1ppt 100000 Measured - 5ppt Measured - 10ppt 90000 Measured - 20ppt 80000

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10000

0 1-Feb-77 29-Mar-77 24-May-77 19-Jul-77 13-Sep-77 8-Nov-77 3-Jan-78

b) Time Step = 1 hour 130000 Modelled - 1ppt 120000 Modelled - 5ppt Modelled - 10ppt 110000 Modelled - 20ppt Measured - 1ppt 100000 Measured - 5ppt Measured - 10ppt 90000 Measured - 20ppt

80000

70000

60000 Chainage (m) A RM 50000 40000

30000 20000

10000

0 1-Feb-77 29-Mar-77 24-May-77 19-Jul-77 13-Sep-77 8-Nov-77 3-Jan-78

COMPARISON OF MEASURED AND MODELLED Figure WRL 13 DEPTH AVERAGED SALINITY

Report No. 2003/01 FEBRUARY 1977 – JANUARY 1978 fig13.doc