In the present study water samples, from various societies of East Zone of Dwarka subcity of New Delhi have been collected where rainwater-harvesting systems are installed. The impact of rainwater harvesting on the amounts of heavy metals in ground water has been studied by collecting water samples from these selected sites in the months before and after the rain. In study the difference between the values of some of the heavy metals in ground water, collected before and after rain, has been found. The present study reveals that the rainwater harvesting suitably reduced the amounts of heavy metals in under ground water and has improved the quality of ground water.