viability of rainwater harvesting techniques for ... · different techniques proposed throughout...

19 September 2018

Viability of Rainwater Harvesting Techniques

for Johannesburg City Parks and Zoo

R. Schmidt, R.P. Verger, K. Scott &

H. Nemavhandu

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Presentation Outline

• Introduction

• South African Guidelines

• Harvesting Techniques

• Case Studies

South African Water Context

• In South Africa water is a scarce commodity.

• Available water resources are under stress.

• Certain areas are frequently declared as drought areas

by government .

• General pressure on water resources could result in

future water restrictions.

• Irrigation of gardens and parks could be seen as a

wasteful extravagance that cannot be afforded.

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Project Introduction

JCPZ wanted to investigate systems that use water

sources such as rainfall and stormwater runoff as an

asset rather than a problem.

There were 27 JCPZ facilities across 7 regions:

• Depots

• Parks

• Zoo

• Nurseries

• Cemeteries

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Project Introduction

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Introduction to WSUD and SuDS

Water Sensitive Urban Design - WSUD

• Focuses on the integration of surface water

runoff/stormwater into the urban water cycle.

• Allows cities to become more resilient to the

pressures on ageing and expensive water

infrastructure

Sustainable (Urban) Drainage Systems – SuDS

• Practical affordable alternatives to stormwater

management

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South African Guidelines

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The Urban Water Cycle

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Due to urbanisation, the urban water cycle has changed

and there is an increase in the runoff generated from

catchment areas.

JCPZ Project

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Rooftop Rainwater Harvesting

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Rainwater harvesting is a process of capturing rainwater

for re-use in a different system instead of letting the

rainwater enter the stormwater system

In-Field Stormwater Harvesting

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In-field stormwater harvesting is used to slow down

runoff to ensure maximum infiltration into the ground

and recharge.

Stormwater Harvesting Techniques

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Underground stormwater harvesting captures

stormwater runoff in underground tank that is stored

for re-use

Case Studies

Five (5) facilities were chosen to demonstrate the

different techniques proposed throughout the

project.

A viability analysis for each proposed rooftop and

underground stormwater harvesting technique was

completed.

Accumulative total cost over the life of the rooftop

rainwater harvesting system was calculated and

compared to the calculated accumulative water

savings over life of system.

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Example 1

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Section Description Amount VAT 14% Total (Incl. VAT)

A Section A: Springfield Depot R 105 890.00 R 14 824.60 R 120 714.60

B Section B: Springfield Street Trees R 48 687.00 R 6 816.18 R 55 503.18

C Section C: Pioneer Park R 32 251.00 R 4 515.14 R 36 766.14

D Section D: Joubert Park R 22 181.00 R 3 105.34 R 25 286.34

E Section E: Metro Park R 22 181.00 R 3 105.34 R 25 286.34

Region F - Total R 231 190.00 R 263 556.60

Preliminary Cost Estimate and Viability

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6 Storage Tanks

Greenhouse Structure

Section Description Amount VAT 14% Total (Incl. VAT)

A Section A: Marks Park Depot R 73 760.00 R 10 326.40 R 84 086.40

B Section B: Zoo Lake Training Centre

R 79 266.50 R 11 097.31 R 90 363.81

C Section C: Johannesburg Zoo R 60 290.00 R 8 440.60 R 68 730.60

D Section D: Westpark Cemetery R 55 525.50 R 7 773.57 R 63 299.07

Region B - Total R 268 842.00 R 306 479.88

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Preliminary Cost Estimate and Viability

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1 Storage Tank

Ablution Structure

Section Description Amount VAT 14% Total (Incl. VAT)

A Section A: Klipspruit Depot R 38 302.50 R 5 362.35 R 43 664.85

B Section B: Orlando West Park R 22 181.00 R 3 105.34 R 25 286.34

C Section C: Petrus Molefe Prescient R 22 181.00 R 3 105.34 R 25 286.34

D Section D: Thokoza Park R 57 783.00 R 8 089.62 R 65 872.62

E Section E: Diepkloof Extreme Park R 22 181.00 R 3 105.34 R 25 286.34

Region D - Total R 194 987.50 R 221 433.60

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Preliminary Cost Estimate and Viability

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Preliminary Cost Estimate and Viability

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Section Description Amount VAT 14% Total (Incl. VAT)

A Section A: Johannesburg Zoo R 1 830 171.2 R 256 223.968 R 2 086 395.168

Region B - Total R 1 830 171.2 R 2 086 395.168

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2 Underground

Storage Tanks

Preliminary Cost Estimate and Viability

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Section Description Amount VAT 14% Total (Incl. VAT)

A Section A: Huddle Park Nursery R 1 166 592.99 R163 323.02 R1 329 916.01

Region E - Total R 1 166 592.99 R1 329 916.01

Conclusions

• Rooftop rainwater harvesting, stormwater harvesting

and in-field harvesting was found to be viable

interventions that JCPZ facilities could implement.

• These interventions promote conservation and reuse

of water in the broader community.

• WSUD and SuDS provides an integrated approach that

is moving away from the conventional stormwater

management systems.

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Recommendations

Integration of rainwater harvesting and water

conservation philosophies into city-wide Stormwater

Runoff Control Plans.

Techniques should be considered in future

developments.

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Thank You