Abstract
The water gravitational vortex turbineiscommonly used in theriver streamto generateelectrical power. However, no work had been donein investigating the performance ofthe water gravitational vortex turbine using rooftop rainwater. The reliability ofthis turbineis still newto beapplied using therainwater sourcethat depends much on climatechange. Thereis an urging necessity to alternatetheelectrical power for renewablesources for sustainable development community. Hence, the preliminary study of the turbine performanceis started at the designing of the turbin eitself