You can help protect the Magothy from your own backyard.  Consider limiting fertilizer application, scooping pet waste, installing a rain garden and minimizing impervious surfaces.  For helpful tips on these and other practices see:

Magothy River Action Tips

From Your Backyard to Our Bay, Anne Arundel County

Being Bay-Wise: Landscaping Tips for a River-Friendly Backyard

10 Things Marylanders Can Do Today to Reclaim the Bay, Maryland Department of the Environment

Rainscaping Chesapeake Ecology Center