Rainfall across Pennsylvania has been far below average this year. But the amount of water making it into the ground is lowest in cities - because pavement locks water out.

Thomas Cahill (Cay-hill) is an environmental engineer in West Chester. He says modern cities are poorly designed for water conservation.

Every time we put up a new box we would surround it with a sea of asphalt. And all the resultant rainwater would run directly off the surface and into a nearby stream and not just flood the stream but prevent that water from getting into the ground and recharging our aquifers.

Cahill says most of the water flowing through Pennsylvania streams comes from underground reservoirs.

Cahill says stormwater can also pick up pollutants as it rushes along the ground. He says there are some methods to slow water down, help recharge groundwater, and reduce contamination.

Cahill works with developers to install vegetated rooftops which act like tiny ecosystems on top of buildings. He also works with porous pavement - asphalt which is designed to let waster slowly seep back into the ground instead of running toward the nearest stream or sewer system.

More information's available on the web at GreenWorks.tv. I'm Brad Linder.