The vulnerability of surface and groundwater catchments to pollution varies significantly depending on a variety of factors including land use, soil type, hydrology, geology, and climate. This is true for a wide range of potential contaminants including particularly pesticides. While blanket controls on potential pollutants and encouragement of general good practice measures will be of some benefit in protecting catchments, truly effective protection can only be achieved by targeted measures based on specific assessment of local vulnerability. For that reason we have developed a novel, computer-based catchment planning system, known as CatchIS. This provides a powerful and flexible system for manipulating a variety of GIS and non GIS databases, in conjunction with specific runoff and leaching models for pesticides and other pollutants. The system provides a powerful management tool for promoting practices which encourage less polluting pesticide use. In addition it offers a number of other significant opportunities for water utility planning purposes.