MANAGED AQUIFER RECHARGE (MAR) FOR STORMWATER MANAGEMENT ON THE - - PowerPoint PPT Presentation

MANAGED AQUIFER RECHARGE (MAR) FOR STORMWATER MANAGEMENT ON THE CAPE FLATS, CAPE TOWN

Benjamin Mauck Supervisor: Kevin Winter 11th November 2015

www.wsud.co.za

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INTRODUCTION

South Africa’s urban areas are becoming increasingly vulnerable to water scarcity.

• Stressed surface water

resources

• Economic Growth
• Population Growth
• Climate change
• Mediterranean climate
• Highly urbanised
• Ecologically sensitive
• Prone to water scarcity

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WATER SENSITIVE URBAN DESIGN

• Sustainable stormwater management (SUDS)
• Reuse of water (i.e. MAR),
• Alternative supply sources (i.e. Groundwater),
• Improving aesthetic and recreational appeal of urban

water.

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WSUD – MANAGED AQUIFER RECHARGE

Stormwater Management Water Supply

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STUDY SITE - CAPE FLATS

Tygerberg Durbanville Kuilsriver

Cape Town

Muizenberg

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CAPE FLATS - GROUNDWATER

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RESEARCH OUTLINE

• The main objective is to test the applicability of

Managed Aquifer Recharge (MAR) on the Cape Flats:

• Integrated modelling approach MIKE SHE/MIKE 11.
• Is it possible to infiltrate winter stormwater into the CFA for

the purpose of stormwater Managment?

• Can this infiltration be optimised by increasing abstractions

from the CFA for fit-for-purpose uses during the summer months?

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Water Quality Urban infrustructure (MIKE URBAN)

MIKE SHE – INTEGRATED HYDROLOGICAL

MODELLING

River flow (MIKE 11) Overland flow and flooding Unsaturated Zone Flow Precipitation Evapotranspiration Saturated Groundwater Flow

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MIKE SHE – INPUTS

MIKE 11 Rainfall Potential Evaporation Land Use Soil Types (UZ) Geology (SZ)

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MIKE SHE – GW LEVELS

Mean Head Elevation Groundwater Levels

R2 = 0.80 R2 = 0.76 R2 = 0.45 R2 = 0.63

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MIKE SHE – HEAD ELEVATION

Simulated

Mean Error = -1.6m Mean Error = -0.4m

Observed

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MIKE SHE – RECHARGE

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MIKE SHE – FLOW

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MIKE SHE – STORMWATER MANAGEMENT?

How much abstraction is needed? How long would it take to refill the aquifer? What are the possible uses for abstracted water?

• High Water

Table

• Urban

Flooding

• Lower Water Table
• Lower Flood Risk
• High summer Demand

How much stormwater can be stored?

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NEXT STEPS…

 Calibrate MIKE SHE at a regional scale:

• 1980 – 1984
• 2010 – 2015
• Compare Model performance
• Select optimal sites for MAR:
• Model output
• Flood mapping
• Land use
• Water Quality
• Scenario simulation using local scale MIKE SHE models.
• Artificial Recharge
• Abstraction (Pump tests)
• Climate Change

THANK YOU

www.wsud.co.za

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CSIR:

• Potable water

supply

• Waste water

treatment

• Re-use

Reviewed again for bulk water supply potential.

CAPE FLATS AQUIFER

• Number of studies since the 1970’s: Henzen,1973; Wessels and

Greeff, 1980; Hay,1981; Tredoux,1983 &1984; Vandoolaeghe, 1989 &1990; Fraser and Weaver, 2000; DWAF 2007 & 2008.

Reviewed for bulk water supply potential. 1970 Early 1980’s 2015/2016 Late 1980’s 2000 2007-2008 DWAF: Berg CMA

• Report. The CFA

was an area of interest. Exploration CFA Hydrogeological Properties.

Increasing CFA Interest:

• UCT, Delta H,

Umvoto, CSIR, CoCT & DWS

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MODEL SELECTION

• Stormwater models (SWMM, MOUSE, P8 or MUSIC) lack detailed

groundwater representation.

• Coupling urban stormwater and groundwater models (i.e. SWMM

and MODFLOW):

• Lack of communication/feedback at each time step.
• DSS - Established urban groundwater Decision Support Systems:
• Data intensive
• Complex model structure
• Integrated hydrological models – MODHMS, HGS, MIKE SHE:
• Fully integrated surface- and ground-water capabilities,
• Spatially distributed,
• Simpler model structure,
• Flexible model requirements (data availability or conceptual model),
• MIKE SHE can link urban stormwater model MIKE URBAN.