Water resources in the tropics and subtropics are under severe pressure from burgeoning populations, ad hoc development, and the degrading environment. Uncertainty in precipitation due to climate change adds to the pressure to equitably provide adequate and safe water to all of humanity. Hence, utilizing the beneficial roles played by forests and wetlands upon water availability and quality is the only way to enable the equitable provision of water to all sections of society as well as for buffering water resources against climate change. Understanding the links between different ecosystems in a catchment and local/regional hydrology enables restoration and maintenance of the ecosystems along with the services they provide. This chapter describes the ecohydrological approach to water resources management along with some examples of the application to a range of areas, from river basin management to wastewater treatment and reuse.