The Philippines, in common with many parts of South-east Asia, has experienced rapid economic development in recent years. The rapid growth in urban population often outstrips the provision of infrastructures for water supply, sanitation and refuse disposal. The long-term sustainability of good quality groundwater resources which are widely used for potable supplies is threatened by this lack of infrastructure.

lf water supplies are to be protected in the medium- and long-term there is an urgent need for the development of a national groundwater protection policy. As tried and tested in the United Kingdom, groundwater vulnerability mapping represents an appropriate. low cost management tool for protecting groundwater. Land is zoned by assessing how quickly pollutants can move from the ground surface down to the water-table by characterising the type of aquifer material, the overlying soil properties and the depth to groundwater.

lt is imperative that groundwater vulnerability maps provide clear guidance in order that they can be used by non-earth science specialists. In this study the classes of groundwater vulnerability shown on the map have been simplified and amalgamated using a matrix of land properties to prepare a more easily understood Development Constraint Map. This map identities four progressively stringent constraint zones where increasing controls on the development of potentially polluting activities will have to be exercised in the future if groundwater quality is to be maintained. The preparation of uncomplicated tools such as this Development Constraint Map ensures that the scientific data implicit in the groundwater vulnerability assessment is taken into account in the decision-making process when prioritising infrastructure investment or exercising development control.