what is a catchment area
In human geography, a catchment area is the area from which a city, service or institution attracts a population that use their services. For example, a school catchment area is the geographic area from which students are eligible to attend a local school. Supermarkets, on the other hand, have a much lower density, with catchment areas of several neighborhoods (or several villages in rural areas). 2  This principle, similar to the central place theory, makes catchment areas an important area of study for geographers, economists, and urban planners.
For the vast majority of tank-based rainwater harvesting systems, the catchment area is the roof surface. There are some important factors about the roof to consider when planning for a RWH system: Roof Material – The material of the roof is not as important as contaminants that may be on the roof.