Excess water from rain events that flows straight into the Bay without soaking into the ground first is one of the biggest sources of water quality problems, especially in urban and suburban areas.  When water does soak into the ground first, vegetation and soils serve as important filtering agents, removing excess nutrients from fertilizers and other pollutants.  When water flows straight into the Bay, it carries with it pollutants and bacteria that can impact the health of Bay organisms, as well as human health, and nutrients that lead to algae blooms and decreased oxygen levels.  The Chesapeake Bay Program estimates that 20 percent of excess nutrients in the Bay are derived from stormwater inputs.

Several techniques can be used by governments, commercial entities, community associations and individual homeowners to reduce storm water input:
- Rain barrels
- Rain gardens
- Bioretention systems

General storm water information:
 - Alliance for the Chesapeake Bay
 - Maryland Department of the Environment
 - Maryland Department of Natural Resources
 - U.S. Environmental Protection Agency

New tools to assist in assessing stormwater impact:
 - Keep the Water Out: A new tool to estimate reductions in stormwater from non-traditional approaches, Jennifer Molloy, U.S. EPA Office of Wastewater Management.  Click here to access the instructions for this tool and here to access the worksheet.
 - Green Infrastructure Calculator: A new tool to assess technical and financial considerations in selecting alternative stormwater management approaches, Scott Bernstein, Center for Neighborhood Technologies.