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The
World
Water
Quality
Assessment
Large-scale water quality modeling
Hot spots and causes of water pollution
The
World
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
The
World
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
The
World
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)
The
World
Water
Quality
AssessmentConnectivity & treatment
The
World
Water
Quality
AssessmentLoadings: Fecal coliform bacteria
Human and animal input
2010
The
World
Water
Quality
AssessmentDilution capacityClimate normal period (1971-2000)
Example:Modeled FC concentration at Mhlatuze River, South Africa January to December 2010
The
World
Water
Quality
AssessmentFC in-stream concentration
February 2010
The
World
Water
Quality
AssessmentComparison: FC in-stream concentration
February 2010 August 2010
The
World
Water
Quality
AssessmentSensitivity analysis: Assuming 100% connectivity……but no improvement of treatment levels
February 2010
The
World
Water
Quality
Assessment
Total BOD loads in 2010~ 8.5 million tons
BOD loadings in 2010
The
World
Water
Quality
AssessmentBOD in-stream concentration
February 2010 August 2010
The
World
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
The
World
Water
Quality
AssessmentSensitivity analysis for BOD: “low rate“ assumption
Total BOD loads in 2010~ 5 million tons
The
World
Water
Quality
AssessmentHot spots of BOD for “low rate“ assumption
February 2010 August 2010
The
World
Water
Quality
AssessmentModel validationHigh: assuming 7.5% of washed-off manure contributes to BOD load
Low: assuming 3% of washed-off manure contributes to BOD load
The
World
Water
Quality
AssessmentCause of water pollution: sources of BOD loads
The
World
Water
Quality
AssessmentTransboundary river basin scaleExample:Total BOD loads in the Nile river basincontributing loads per country [%]
The
World
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
The
World
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
The
World
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
