International discussions on the demand responsive approach (DRA) started in the mid-1990s because past supply-driven approaches had led to the failure of many water supply and sewerage/on-site sanitation (WS&S/OS) projects in developing countries (DCs). DRA has already been adopted in many WS&S/OS projects targeting a certain rural or poor urban area(s) by using various demand assessment techniques such as participatory rapid appraisal (PRA) to select optimum technical options. However, adoption of DRA in large-scale urban WS&S/OS projects (covering various areas of different socio-economic groups with different needs) has been relatively delayed. Recently, the participatory geographic information system (PGIS) has emerged as an effective method of PRA, and high resolution satellite imagery (HRSI) has become commercially available. This paper presents a PGIS-based visual area categorization of different income groups using HRSI as a key for expediting the adoption of DRA to large-scale projects in DCs. This paper proposes an innovative pro-poor methodology of DRA for large-scale urban WS&S/OS projects. The methodology focuses on the improvement of multistage sampling in a household sample survey to plan mixed services suitable for various groups. The results of a partial application of the methodology in Pakistan are also presented.
Keywords: demand responsive approach, developing countries, high resolution satellite imagery, participatory GIS, sewerage, water supply