Apart from the Bhatsa Dam, six major lakes supply water to the city: Vihar, Vaitarna, Upper Vaitarna, Tulsi, Tansa and Powai. Tulsi Lake and Vihar Lake are located in Borivili National Park, within the city's metropolitan limits. The supply from Powai lake, also within the city limits, is used only for industrial purposes. Three small rivers, the Dahisar, Poinsar (or Poisar) and Ohiwara (or Oshiwara) originate within the park, while the now infamous Mithi River originates from Tulsi Lake and gathers water overflowing from Vihar and Powai Lakes. The coastline of the city is indented with numerous creeks and bays. The eastern coast of Salsette Island is covered with large mangrove swamps, rich in biodiversity. The western coast is mostly sandy and rocky.

Soil cover in the city region is predominantly sandy due to its proximity to the sea. In the suburbs, the soil cover is largely alluvial and loamy. The underlying rock of the region is composed of black Deccan basalt flows, and their acid and basic variants dating back to the late Cretaceous and early Eocene eras. Mumbai sits on a seismically active zone owing to the presence of three fault lines in the vicinity. The area is classified as a Zone III region, which means an earthquake of up to magnitude 6.5 on the Richter-scale may be expected.