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Large- scale water quality modeling. Hot spots and causes of water pollution. The modeling framework Model results for Africa Progress since October 2013 Hot spots of water pollution Fecal Coliform bacteria Risk to human health BOD Threat to inland fishery - PowerPoint PPT Presentation
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The
World
Water
Quality
Assessment
Large-scale water quality modeling
Hot spots and causes of water pollution
TheWorld Water Quality Assessment
• The modeling framework• Model results for Africa
– Progress since October 2013• Hot spots of water pollution
– Fecal Coliform bacteria Risk to human health– BOD Threat to inland fishery
• Causes of water pollution– Main sectors contributing to pollution
• Conclusions & preliminary findings• Next steps
Outline
TheWorld Water Quality AssessmentModeling framework
WaterGAP3Water Use Models
agriculture domestic manufacturing electricityproduction
consumptivewater use return flow
WaterGAP3Hydrology Model
spatial: 5’temporal: dailyresults: daily/monthly
WorldQualWater Quality
Model
spatial: 5‘ temporal: daily results: daily/monthly/yearly
spatial: 5’temporal: monthlyresults: monthly
discharge, runoff, flow velocity
TheWorld Water Quality AssessmentProgress since October 2013
agriculture(industrial fertilizer)
natural back-ground
agriculture(organic fertilizer)
diffuse sources
domestic– septic tanks– pit latrines– inadequate
sanitation
manufacturing (wastewater)
urbansurface runoff
domestic (urban)– sewage
point sources
domestic (rural)– sewage– hanging
latrines
“scattered settlements”
Data from Joint Monitoring Programme; country files (1980-2011)
TheWorld Water Quality AssessmentConnectivity & treatment
TheWorld Water Quality AssessmentLoadings: Fecal coliform bacteria
Human and animal input
2010
TheWorld Water Quality AssessmentDilution capacity
Climate normal period (1971-2000)
Example:Modeled FC concentration at Mhlatuze River, South Africa January to December 2010
TheWorld Water Quality AssessmentFC in-stream concentration
February 2010
TheWorld Water Quality AssessmentComparison: FC in-stream concentration
February 2010 August 2010
TheWorld Water Quality AssessmentSensitivity analysis: Assuming 100% connectivity…
…but no improvement of treatment levels February 2010
TheWorld Water Quality Assessment
Total BOD loads in 2010~ 8.5 million tons
BOD loadings in 2010
TheWorld Water Quality AssessmentBOD in-stream concentration
February 2010 August 2010
TheWorld Water Quality AssessmentUncertainty of model assumptions
High: assuming 7.5% of washed-off manure contributes to BOD load
Low: assuming 3% of washed-off manure contributes to BOD load
TheWorld Water Quality AssessmentSensitivity analysis for BOD: “low rate“ assumption
Total BOD loads in 2010~ 5 million tons
TheWorld Water Quality AssessmentHot spots of BOD for “low rate“ assumption
February 2010 August 2010
TheWorld Water Quality AssessmentModel validation
High: assuming 7.5% of washed-off manure contributes to BOD load
Low: assuming 3% of washed-off manure contributes to BOD load
TheWorld Water Quality AssessmentCause of water pollution: sources of BOD loads
TheWorld Water Quality AssessmentTransboundary river basin scale
Example:Total BOD loads in the Nile river basincontributing loads per country [%]
TheWorld Water Quality Assessment
First time: Synthesize information about population, sanitation and
connectivity and make spatially explicit for all of Africa Compute loads of organic pollution and bacterial
contamination for each river basin in Africa (grid cell basis)
Geographic comparison of BOD and fecal coliform loadings in Africa
Calculation of BOD and coliform levels for all rivers in Africa
Estimation of hot spot water pollution areas in Africa
Conclusions
TheWorld Water Quality Assessment
Hot spot areas: 17% of population living at big rivers with bacterial contamination >1000cfu/100ml in Africa
Hot spot areas: Dilution capacity + magnitude of loadings Magnitude of BOD loading uncertain (manure runoff) Most important source of BOD: manure runoff; least important:
urban surface runoff Source profile of BOD loadings vary greatly between countries
(e.g. Somalia: manure runoff; Egypt: urban domestic) Total BOD loads steadily increased in Africa between 1990 and
2010 (increasing population, livestock, connectivity) High potential to provide policy-relevant overview of water
quality issues for Africa and other regions
Preliminary findings
TheWorld Water Quality Assessment
Further improvement of estimates for Africa – getting regional feedback
Extension of estimates to Asia and Latin America Extension of estimates to include:
– other water quality parameters (total dissolved solids, total N, total P, water temperature)
– lakes
Apply water quality guidelines as thresholds Merger of model-driven & data-driven analyses: threats
to human health & inland fisheries (food security ) and policy responses
Next steps
