SWITCH Training Kit: Pilot Training, Entebbe, 28-29 July 2010

Water Demand Management in the City of the Future

Forecasting water demand – why is accurate demand forecasting important?

Why demand forecasting?

To develop a projection or ‘reference case’ of future water demand in a given region

To help understand the gap between supply and demand Time

Water Surplus

DeficitGap

What factors affect demand for water?

Average Demand and Peak Demand Demand management is mainly concerned

with consumption of water resource per yearo i.e. average demand

Short-term fluctuations in demand o Time of year / temperature (higher in hot periods)o Days of the week (variation in commercial /

institutional / industrial / household / tourism uses)o Time of dayFluctuations in demand often managed using storagePeak demand determines system design, and

management of peak demand may be valuable

Water Demand has many components!

Historical demand forecasting Historical/current per person water demand (l/p-d)

o Historical growth in demand Forecast water demand by multiplying the per person

demand by projected population It is a quick and easy method Limitations

o Only projecting current/past situation which may have been affected by ‘other factors’ such as climate

o Does not account for changes in consumption Changes in use – e.g. showers, flush toilets, washing m/cs Changes in technology and efficiencies

Inaccuracies of historical demand forecasting, example from Sydney

Comparison of methods of demand forecasting

Demand chart

Sector - System Analysis

Sectors and customers

End-use analysis Separate water demand into different sectors (e.g.

residential, industrial) Separate residential into end uses (e.g. showers,

toilets) and estimate change over time Benefits

o Detailed understanding of ‘how’ water is used and how this may change over time

o Uses the concept of the ‘unit of service’ and not just ‘supplying a volume of water’

Limitationso Data on end uses may not be availableo Full analysis requires a major effort (but useful results

and priorities may be obtained through limited study)

End use data from SWITCH Alexandria workshops

Data collection for demand forecasting

The System – Service Provider Bulk

waterMetered water

Other supplies

The System – The customer Demographic data

Stock data

End-use data

•Surveys•Other Govt Statistics

•Questionnaires•Surveys•Data loggers•Diaries•Other studies

•Surveys•Other Govt Statistics

•Surveys

Example of End Use Consumption

Residential end-uses to consider / collect data for analysis

Indoor end useso Toileto Batho Showero Wash basino Laundry tapo Washing machineo Kitchen tapo Dish washer

Outdoor end useso Lawn/garden irrigatno Livestock o Car washingo Pool etco Evaporative AC

Home business useo Tea shop, Hair

salon, Brewing etc

How much water is used?

Toilet water usage projections for Sydney, Australia

Single residential household demand(700 m3/hh/a) – Alice Springs, Australia

Forecasting using end use analysis

Acknowledgements

Sam Kayaga, WEDC UK Stuart White and Andrea Turner,

Institute for Sustainable Futures, University of Technology, Sydney, Australia