Mr. Paul Reiter of the International Water Association presented on the growing urban population and need for water and sanitation systems. By 2050, 155,000 more people will need services in urban areas each day, with 90% of growth occurring in developing countries. Municipalities must decide between centralized, integrated systems or more localized, on-site solutions. There are tradeoffs between control, costs, efficiency, capacity and other constraints to consider for combined sewer, storm drain, or ditch and culvert systems. Policy has shifted over time towards natural systems that guide water quality and landslide prevention.

1. Combined vs. Separate Systems:
What Works for You?
Mr. Paul Reiter
International Water Association (IWA)
Asia Water Week

3. The Urban Arithmetic for 2050
• 155 000 persons per day155,000 persons per day
• 90% in developing countries
90% i b• ~90% in urban areas
• ~800,000 per week in urban settings
• X 52 weeks per yearX 52 weeks per year
• X 40 years

4. CRISIS
=
DANGER + OPPORTUNITY

5. The Decision Space
Highly Centralized,
Highly Integrated
Level of
Integration
On-Site
Scale

6. The Decision Space
Highly Centralized,
Highly Integrated
Level of
Integration
On-Site
Scale

7. The Decision Spacep
Highly Centralized,
Level of
Physical
Integration
Highly Integrated
Semi-Centralized
On-Site
Semi Centralized
Highly Efficient
Scale

8. The Decision Spacep
Highly Centralized,
Level of
Physical
Integration
Highly Integrated
Semi-Centralized
On-Site
Semi Centralized
Highly Efficient
Scale

9. Three Types of Systems
Ditch and CulvertDitch and Culvert
Combined Sewer
Storm Drain

10. Evolution of Policy
1987 Formed drainage utility following1987 Formed drainage utility following
100-year storm
1995 Stormwater plan begins guiding1995 Stormwater plan begins guiding
water quality program
1996 City’s role in landslide prevention1996 City s role in landslide prevention
strengthened
2001 Shift to natural systems underwayy y

11. Major Issues
• ControlControl
• Costs
ffi i• Efficiency
• Capacity
• Other constraints