Water Supply & Sanitation Working Notes

Water Supply & Sanitation Working Notes are published by the Water Supply and Sanitation Sector Board of the Infrastructure Network of the World Bank Group. Working Notes are available on-line: www.worldbank.org/watsan. Working Notes are lightly edited documents intended to elicit discussion on topical issues in the water supply and sanitation sector. They disseminate results of conceptual work by World Bank staff to peer professionals in the sector at an early stage, i.e. "works in progress". Comments should be emailed to the authors. 38897