With the accelerated development of urban rainwater utilization in China

theoretical design andcalculation of rain tanks have been studied and reported widely.However

improvements are still required torealize efficient rainwater collection and utilization.Based on current design of rain tanks and rainfall characteristics of semi-arid area

a daily rainfall-water usage balance model was established by analyzing of dailyrainfall in Tianjin City.A reasonable volume of rainwater tanks calculated by a computer program with respect to different water usage conditions.This balance model not only provides a design basis for rain watertank deployment

but also plays an important role for source pollution control and flood peak adjustment.