Effects of urbanisation on aquifer recharge and superficial runoff in the Sumare and Pompeia basins, Sao Paulo Municipality, Brazil

This paper presents the results of a study of aquifer recharge in an area with a high degree of urbanisation, located in Sao Paulo Municipality. The method adopted for estimating direct recharge was measurement of seasonal phreatic levels. Indirect recharge by physical losses in the potable water distribution system was also considered, and these losses represent eight times the value of direct recharge from rainfall. The runoff volumes produced by a specific critical rainfall were also estimated. The use of domestic microreservoirs for temporary storage of rainwater, made obligatory by a municipal law for buildings constructed from 1992 onwards, would retain about 30% of the minimum ideal volume required. The results showed a significant decrease of direct recharge caused by urban impermeabilization, the high potential of indirect recharge by potable water losses in the distribution pipes and the need to extend this municipal law to constructions made before 1992.