Rivers and streams don't fall neatly within city and county boundaries. Many of the streams are shared by Baltimore County and Baltimore City. The headwaters of the Gwynns Falls and Jones Falls, for example, are in Baltimore County but the streams flow to the harbor. Herring Run begins in the County, meanders through the City, and finally empties into the Back River in the County. Drinking water is another shared resource. The Prettyboy, Liberty and Loch Raven Reservoirs are owned and managed by Baltimore City, but are located in Baltimore County. They provide drinking water for much of the Baltimore Metropolitan region. Since 1984 the local governments in the region have worked cooperatively to protect the drinking water reservoirs. The Reservoir Agreement became a sort of model for the Watershed Agreement.

In October 2002, Baltimore City and Baltimore County, Maryland signed a historic Watershed Agreement that unified the City and County efforts to protect watersheds that are located in both jurisdictions. The agreement calls for establishing common goals for managing the natural resources of shared watersheds; improved coordination of resource management strategies and restoration programs; joint meetings with citizen-based watershed associations and annual "state of our watersheds" reports. One of the first projects that resulted from this historical agreement was the Gwynns Falls Water Quality Management Plan. The Gwynns Falls watershed begins in western Baltimore County and drains into Baltimore City. The headwaters are located in rural/suburban Glyndon, Maryland and the stream drains to the tidal area of the Middle Branch of the Patapsco River in downtown Baltimore. The Patapsco Middle Branch is in the western part of the Baltimore Harbor and ultimately drains into the Chesapeake Bay. Approximately two thirds of the watershed lies within Baltimore County and one third lies within Baltimore City. The Water Quality Management Plan was used for partial fulfillment of the federally mandated National Pollutant Discharge Elimination System Permit (NPDES) and to provide a watershed restoration framework for both jurisdictions.

Watershed Agreement