Bringing engineering to life

Bolin Bolin Integrated Water Management Project

Navigating the complications of multiple stakeholders

October 2018

Presentation Outline

1.0 - Introduction

2.0 – Project Description

3.0 – Water Balance Modelling

4.0 – Discussion

Introduction

Stakeholders

Stakeholder Interest

Manningham City CouncilProject partner, operator and water user to irrigate

Bulleen Park including sports fields (part of $1.25M)

Boroondara City CouncilProject partner and water user to irrigate Freeway

Golf Course (part of $1.25M)

Carey Baptist Grammar SchoolProject partner and water user for numerous sports

fields (part of $1.25M)

Melbourne Water Project funding ($960K) and river extraction authority

Parks Victoria Project funding ($7K) and owners of Bolin Bolin site

Federal Government Project funding ($196K)

Dept of Land Water & Planning Project funding ($400K)

System Schematic

Bolin Bolin

StorageBulleen/Carey

Tanks

Golf Course

Storage

P

Irrigation

Pump

25L/s 35L/s

17L/s

P

P

P

35L/s

Northern Catchment

Runoff

P

P

Proposed Pump

Existing Pump

P10L/s

Overflows to Yarra via

wetland or direct

Project Constraints

• Cost

• Protection and retention of trees in an environmentally

significant area

• Power limitations

• Geotechnical challenges with poor and contaminated

soils

• Time – tight constraints on delivery of the design

• Development is on flood prone lands

Project Description

Location

Waverly

Oval

Bulleen Park & Carey Grammar Tanks (0.4ML)

Golf Course Storage

Yarra River Extraction Pump (Existing)

Bolin Bolin Storage Storage (1.5ML)

Transfer Line

P

P

P

P

System Overview

Bolin Bolin Storage Capacity 1.5ML (nominal);

Stormwater harvesting from the

northern catchment;

Water quality improvement.

Bulleen Park / Carey Grammar Tank StorageCapacity 0.4ML ;

Fill from Bolin Bolin (priority);

Fill from Golf Course storage (secondary supply).

Golf Course storage Capacity 8.0ML (originally 3ML, then 10ML proposed) ;

Inflow from the Bolin Bolin storage;

Fill from Yarra River under license (secondary supply); and

Direct irrigation of Golf Course – Pump to irrigation pumps directly.

Process Diagram

Note: Ignore the numbers as they are pre-commissioning and are not calibrated.

Water Demands

^Significant increase due to recently constructed golf course irrigation system upgrade

Area NameOriginal Demand

(Feasibility Study)Revised Demand

Bulleen Park 14.4 ML pa 14.4 ML pa

Carey Grammar 18 ML pa 18 ML pa

Freeway Golf Course 20 ML pa 90 ML pa^

Total 52.4 ML pa 122.4 ML pa

Water Sources

• Harvested stormwater– Northern Catchment (No Trinity Grammar Overflows); and

– Treated and pumped to Golf Course storage with priority fill of

Bulleen / Carey tank farm.

• Yarra River extraction under licence– Secondary supply when stormwater is not available; and

– Stored in Golf Course storage.

Water Balance Modelling

Water Balance

• The water balance aims to:

– Determine the storage behaviour of the proposed system;

– Evaluate the sensitivity of the system to varied storage capacities,

pump rates and trigger levels etc;

– Determine the reliability of irrigation supply; and

– Determine the mix of stormwater and Yarra water used.

• Based on historical rainfall and Yarra River flow data.

• A 6-minute time-stepped water balance model

Water Balance Inputs – Irrigation Demands

• Irrigation Demand, based on:

– Irrigation at night;

– Calibrated crop factors and irrigation deficit triggers;

– Evapotranspiration for each time-step;

• Irrigation demands varied each year

– Highest demand for dry years (Year 3 - 123 ML); and

– Lower demand for mean years (Year 10 – 105ML);

Water Balance Inputs – Water Sources

• Rainfall data for dry & mean rainfall years:

Water

Balance ID1 2 3 4 5 6 7 8 9 10 11

Year 2008 2002 1983 2004 1982 1999 1978 2000 1980 1995 1991

Rainfall

(mm)411 426 447 447 475 476 611 623 631 669 691

Period Dry Mean

• Yarra River Level data:

• Based on historical flows corresponding to the rainfall years

modelled;

• Graduated Extraction Rates (Cut-off 200ML/day);

Irrigation Demands

Year No. Year Rainfall (mm) Total Irrigation Demand (ML)

1 2008 411 123

2 2002 426 106

3 1983 447 116

4 2004 447 114

5 1982 475 108

6 1999 476 113

7 1978 611 108

8 2000 623 114

9 1980 631 110

10 1995 669 104

11 1991 691 107

Water Balance Inputs – Water Sources

• Yarra River data

– River flows used that correspond to rainfall years;

– Extraction occurs from existing pump (golf course) at 25 L/s;

– Daily Extraction Limit typically 5% of annual licence; and

– Restriction and Bans apply as defined below.

Yarra River Trigger 2 Trigger 1 Ban

Period ML/d ML/d ML/d

High flow 600 450 350

Low flow 600 300 200

Daily Extraction Limit: 50% 25% 0%

Water Balance – Sensitivities

Catchment Harvesting

• Harvesting/Yield depends on:

– Size of storage;

– How much runoff it gets (size & nature of catchment);

– Irrigation regime;

– Upstream demands (Southern catchment);

– Timing of rainfall events ;

Rainfall vs Yield

15

20

25

30

35

40

45

400 450 500 550 600 650 700 750

Sto

rmw

ate

r H

arv

est

ed

(M

L)

Annual Rainfall (mm)

Low rainfall, high harvest

Average rainfall, low harvest

Year 3 (1983)

Rainfall & Storage Size

• 1 Outlier Year & 2 Typical Years Modelled :

– Year 3 (447mm – Dry, poor distribution, worst in range)

– Year 5 (475mm – Dry, more typical distribution) and

– Year 10 (669mm – Ave/Mean rainfall) selected as typical

0

10

20

30

40

50

60

70

80

90

100

3 (1983) 5 (1982) 10 (1995)

Reli

ab

ilit

y (

%)

Year

1.5 ML

3 ML

6 ML

10 ML

Yarra River Extraction Trigger Level

• Trigger Level (Golf Course Storage):

– Yield insensitive to trigger level in average years

– Lower trigger level – More stormwater used;

– High trigger level – Less stormwater used;

– High trigger increased reliability in dry years;

Bolin Bolin

Storage

Golf Course Storage

Yarra River

20 % trigger

100 % trigger

0

10

20

30

40

50

60

70

80

90

100

1 2 3 4 5 6 7 8 9 10 11

Reli

ab

ilit

y %

Year20 % Trigger Level 100 % Trigger Level

1.5ML

Trigger Level Reliability SensitivitiesYear 5 – 475mm (Dry)

40% Trigger

81.5% Reliability

37% Stormwater – 63% Yarra Extractions

100% Trigger

88.5% Reliability

25% Stormwater – 75% Yarra Extractions

Trigger Level Reliability SensitivitiesYear 10 – 669mm (Average)

40% Trigger

98.9% Reliability

27% Stormwater – 73% Yarra Extractions

100% Trigger

100% Reliability

15% Stormwater – 85% Yarra Extractions

Water Supply Composition

• Higher trigger level reduces opportunity for stormwater harvesting

• Dry years are more sensitive to reliability difference, however, lower

trigger level allows more harvesting

• Mean year achieve > 90% reliability for both triggers

Period Year Trigger Level (40%) Trigger Level (100%)

SW

(ML)

Yarra

(ML)

Reliability

(%)

SW

(ML)

Yarra

(ML)

Reliability

(%)

Dry 3 (1983) 26.4 26.5 40.7 19.5 43.6 48.2

5 (1982) 34.9 58.7 81.5 26.2 77.7 88.5

Mean 10 (1995) 28.7 75.7 99.8 16.4 90.5 100

Water Balance Results

• Stormwater yield increases with lower trigger levels,

however, reliability decreases in lower rainfall years.

• Mean years

– Predominantly provide >90% reliability; and

– 3 ML provides good balance between capital investment and

reliability.

• Dry years

– Depends on year/rainfall patterns;

– Significant improvements with increased storage and higher

storage level triggers; and

– Adjusting trigger level can increase reliability without major

capital investment.

Recommendations

• Golf Course storage 3 ML with 40% trigger level

– Best balance of yield and reliability

– Golf course preferred 10ML

– Only 8ML was feasible due to geotechnical issues

• Install control system

– To help manage trigger levels and alarms; and

– Enable adjusting of trigger level when required.

Discussion

Final Solution (that we are aware of)

• Water Supply:

– >90% Reliability;

– Enables irrigation by all parties at night;

– Reduced Yarra River reliance

• System Arrangement:

– 1.5ML Bolin Bolin Storage;

– 8.0ML Golf Course Storage;

– Integrate existing golf course river extraction pump

station;

– 40% river extraction trigger level (adjust during

operation to find optimum);

Stakeholder challenges

• Complex planning permit – long delays (land tenure)

• Conflicting desires

– Melbourne Water wishes to reduce pollutants by utilising more

stormwater. However the irrigators wish to use more river water

as the reliability is higher.

– Golf course want storage always full for aesthetic and golf

reasons but this limits volume of stormwater utilised

– Melbourne Water wants return of extraction licenses however

this imposes more risk on the irrigators and the perception they

are losing access to water.

– Melbourne Water wanted assets above the flood level but there

were compromises to align with Council’s risk appetite

• Changing of staff in the various organisations

• Varying levels of understanding the project and other

employer pressures