An environmental agency wants to evaluate the effectiveness of rain gardens in reducing the impact of urban runoff from an impervious parking lot and from the roof of the building. The parking lot is slightly sloped so the rainwater flows toward the gardens. The runoff from the roof is collected by various downspouts and directed toward the gardens. Scientists at the agency plan to monitor the effectiveness by measuring the water quality of the storm water as it moves through the gardens during and after storm events. Which of the following would be the best measure to use to determine the effectiveness of the rain gardens in reducing the impact of urban runoff?
A) The size and shape of the rain gardens
B) The intensity and duration of the storm event
C) The speed and volume of the water exiting the gardens
D) The temperature of the parking lot and the roof