RAINWATER HARVEST- A SUSTAINABLE URBAN WATER SUPPLY OPTION IN HUMID TROPICS

Urbanization of small towns in Nigeria has led to anthropogenically engendered irreversible environmental degradation, creating peculiar problems for its inhabitants. Case studies of new urban areas in humid southwestern part of Nigeria reveal that rain water harvest is a sustainable option for water supply. Geoenvironmental evaluation of newly developing towns based on field mapping, aerial photo studies and grain size charcterization of underlying Quaternatery deposit reveal that flood catastrophies experienced are a consequence of the following: 1. Rapid urbanization of small town result from fast population increase, force human occupation of flood prone areas. 2. Massive destructive alteration of natural ecosystem in the process of urbanization, altered natural flow systems, surface processes and rainwater infiltration. 3. Bad planning and indiscriminate erection of walls and housing structures block flow channels to form big floods. 4. Bad refuse disposal schemes marked by indiscriminate dumping of solid waste and thrash in drainage and stream channels results in clogging of flow path of rainwater and pollution of surface water systems. 5. Absence of sewage proper disposal system cause pollution of surface and ground water systems rendering them unfit for human consumption and contributing to the growing scarcity of fresh water and degeneration of sanitary conditions in urban areas. Rainwater harvest by direct collection from rooftops into large surface storage tanks or in encased wells will provide essential clean water at least for domestic consumption. It is becoming more apparent that the need for water supply policy should include rainwater harvest for water supply in urban areas in humid tropical countries of the world.