Lachlan Valley eWater Source Model Development

Gurmeet Singh

1 Outline of presentation

• Introduction • Key Objectives for Lachlan Valley model development • Catchment overview • Hydrology- eWater Source Sacramento Model Development • Results • Conclusions Objectives

• The aim of this project is to develop planning model to undertake investigations into potential storages in the Lachlan Valley to meet Water Security in the region.

• As part of this project we have developed Rainfall/Runoff models for estimation of long term inflows for planning models. This presentation is about the development of Rainfall/Runoff models in eWater Source for the Lachlan Valley. Valley Model Development

Key Objectives

• To develop Lachlan Valley Planning Model in eWater Source for investigating alternate storage options for Centroc Region (that includes Lachlan ).

• Run model to set up baseline for water security in the Lachlan Valley and the Centroc region

• Undertake Water Resource allocation and run long term models for varied scenarios considering climate change

• Investigate alternate sources to increase water security using the planning models Introduction

Lower Lachlan Mid Lachlan

Upper Lachlan

•Intermittent River, End of system- Great Cumbung Swamp, connects during extreme floods •Catchment Area 8300 km2 •Large and Wide floodplain > 100 km •Several lakes, billabongs, anabranches in floodplain that interact with Introduction

Wyangala is situated on the Lachlan River about 35 km south- east of Cowra in the central .

Wyangala Dam Construction completed 1971 Type of Embankmet Rock and Earthfill Spillway 8 Radial Gates Maximum Height (m) 82.3 Full Supply Level mAHD 378.8 Crest level (m) 385 Storage Capacity at FSL (GL) 1220 Introduction

Carcoar Dam is situated on the about 6 kilometres upstream of Carcoar town in Central West NSW.

Carcoar Dam Construction Completed 1970 Type of Emabankment Concrete Arch

Spillway Free overflow over dam crest Maximum Height (m) 52 Fulll Supply Level mAHD 847.2 Crest Level (mAD) 852.1 Storage Capacity at FSL (GL) 35.8 Off-River (re-regulating) Storages

Lake Carregiliigo Lake Brewster Capacity 36 GL Capacity 154 GL

These storages for used for meeting downstream demands in tandem with headwater storages Mean Annual Rainfall

Annual Rainfall- range from 300-900 mm/yr Mean Annual Evaporation

Annual Evaporation- range from 1100- 2000 mm/yr Landuse

Grazing and Dryland cropping are largest users mostly confined to Mid Lachlan region HYDROLOGY

This presentation includes: • Overview of the gauged and ungauged tributaries in Lachlan River • Information on gauged data record and summary of models that have been calibrated. • Catchment delineation and calibration strategy • Presentation of model results for few selective large wet and dry contributing tributary catchments. • Conclusions Sacramento Rainfall Runoff Models for Lachlan Valley

• Rainfall Runoff model catchments shown in Colour

• Grey hatched areas indicates residual or ungauged catchments Catchment Models Delineation • Gauged/Ungauged catchments Total Area Period of %Flow Calibrated Tributaries No. km2 Record contribution Upstream of Upstream of 4 8290 45-86 years 40% Upstream of Carcoar Dam 1 233 20 years 1%

Downstream of Dams Tributaries_Belubula River 5 634 15-48 years 5% Tributaries Lachlan River 10 12,971 20-77 years 39%

Ungauged residuals +Tributaries 18 18,640 15% Rainfall Runoff Models

• Data used for calibration (BOM gridded data- Potential Evapotranspiration (PET) and Rainfall- 1900-2014 • Modelled daily time step • Record length used for calibration (20-44 years) • Extraction data on the tributaries (if any) • Calibration Strategy (Automated calibration first using SCE then Rosenbrock)+ Fine tune with Manual adjustments • Quality (Goodness of fit for calibration)- NSE, Daily, Monthly and Annual statistics within acceptable range. • Residual Catchments- using the calibrated parameters from adjoining catchments and similar soils Wyangala Dam Inflows

1969-2016

Flows are back calculated at the Dam using stage, rainfall and evaporation, the reliability of estimation is poor for low flow range

ML/d Recorded Simulated %diff Daily Mean ML/d 1416 1340 5.40% Flows Monthly Mean ML/mth 43235 40967 5.10% Annual Mean ML/year 498661 491624 1.40% Daily Flow Stats NSE Daily 0.79 NSE Daily log flow duration 0.87 %Volume difference -5.1 Pearson's Correlation 0.95

% Exceeded • Validation Pre-Dam 1917-1928 at Gauge 412027

Recorded Simulated %diff Daily Mean ML/d 1679 1632 2.8% Monthly Mean ML/mth 51207 52350 2.2% Annual Mean ML/year 699787 689931 1.4% Daily Flow Stats NSEDaily 0.751 NSE Daily log flow duration 0.803 %volume difference 2.2 Pearson's Correlation 0.84

% Exceeded Calibration-upstream of Carcoar Dam

Belubula River@ Blayney- Gauge 412105

1992-2004

Recorded Simulated %diff Daily Mean ML/d 26.7 25.4 4.8% Monthly Mean ML/mth 846 821 3.0% Annual Mean ML/year 7206 7120 1.2% Daily Flow Stats NSE Daily 0.69 NSE Daily log flow duration 0.73 %volume difference -4.6 Pearson's Correlation 0.74 Calibration- Carcoar Dam Inflows

2001-2016

Recorded Simulated %diff Daily Mean ML/d 27.06 26.23 3.0% Monthly Mean ML/mth 1802 1762 2.2% Annual Mean ML/year 16379 16714 2.0% Daily Flow Stats

NSE Daily 0.7 NSE Daily log flow duration 0.72 %volume difference -3.1 Pearson's Correlation 0.743

Flows are back calculated at the Dam using stage, rainfall and evaporation, the reliability of estimation is poor for low flow range Calibration Downstream Tributaries (Wet catchments) Boorowa Creek Catchment area 1810 km2

1970-2014

Recorded Simulated %diff Daily Mean ML/d 263 267.31 1.6% Monthly Mean ML/mth 7891 8003 1.4% Annual Mean ML/year 104369 103141 1.2% Daily Flow Stats NSE Daily 0.71 NSE Daily log flow duration 0.851 %volume difference 1.8 Pearson's Correlation 0.852 Flows Flows ML/d

% Exceeded Calibration plots for Boroowa River

Mass Residuals Plot Scatter Plot- Simulated=0.98*Observed

Daily Time Series Cumulative Plot Calibration Downstream Tributaries (Wet catchments)

Mandagery Creek Catchment area 1693 km2

1970-2014

Recorded Simulated %diff Daily Mean ML/d 178.2 178 0.1% Monthly Mean ML/mth 5380 5416 0.7% Annual Mean ML/year 65379 65694 0.5% Daily Flow Stats NSE Daily 0.78 NSE Daily log flow duration 0.86 %volume difference -0.1 Pearson's Correlation 0.86 Calibration Downstream Tributaries (Dry catchments) Back Creek Catchment area 808 km2

Calibration period 1975-2009

Recorded Simulated %diff Daily Mean ML/d 33.7 35.1 4.2% Monthly Mean ML/mth 2090 2153 3.0% Annual Mean ML/year 25165 25845 2.7% Daily Flow Stats NSE Daily 0.68 NSE Daily log flow duration 0.72 %volume difference 4.0 Pearson's Correlation 0.74 Conclusions

 The hydrology undertaken for Lachlan Valley for estimating long term inflows has been completed. The inflows are being used in developing the planning models. A total of 15 downstream calibrated tributaries have been included (total contribution to Lachlan Annual Mean flows 44%).

 The residual and ungauged catchment in both river and tributaries has been modelled using Sacramento model parameters from adjoining calibrated catchments and based on similar soils. The models will be validated with subsets of calibration period used.

 Flow replication at River Gauges has shown promising results especially at low flows. The effort put in the hydrology is evident in the good replication of flows at the key river gauges along the Lachlan River.

 Next stage is development of demand and water resource allocation models. Questions?

ACKNOWLEDGEMENTS

My sincere thanks to the following for providing me opportunity and support for this project:

• Executive Manager, Strategic Engineering- Mr Andrew George • Manager, Water Modelling, Mr Mahes Maheswaran • Manager, Assets Strategy, Mr Andrew Fraser • All the Water Modelling Team, WaterNSW for their support and assistance