We plan to do a Rain Water Harvesting project in Panchkula, Haryana wherein we intend to harvest the rain water from asphalt/bitumen roads and divert them to desilting chambers and then recharge borewells. In the process, we need to estimate the runoff that'll be collected from the roads. So my question is
1. What is the run-off coefficient considered for Asphalt/bitumen roads? Is it 0.7, 0.8 or higher?
2. Also, if the roads are daily swept clean and there is no vehicular movement on them, will the quality of water still be low considering that asphalt roads contain lot of organic compounds in the aggregate that's used to make these roads?