The area of the Prettyboy Watershed is approximately 80 square miles. The drainage area extends from the southern reaches of York County, PA and the northeastern corner of Carroll County, MD into the northwestern corner of Baltimore County where it drains into the Prettyboy Reservoir. The municipalities of Hampstead and Manchester make up the western edge of the watershed.

Land Use
It is a largely rural watershed. Fifteen percent of the region is developed and this percentage is growing. Agriculture makes up 47% of the area, with most of that land planted in crops, the remaining in pasture. Forests, wetlands and water take up the remaining 38% of the watershed.

Land Ownership
Baltimore City owns 14.5% of the watershed totaling 7380 acres. The Prettyboy Reservoir encompasses approximately 1500 of those acres.

Drinking Water Supply
The Prettyboy Reservoir, along with Loch Raven Reservoir that is downstream, provides 61% of the drinking water for the entire Baltimore Metropolitan system. For this reason, the Prettyboy is considered a "source water" or drinking water watershed. The residents of the watershed receive their drinking water from groundwater from private wells or the municipal wellheads of Hampstead and Manchester .

Maryland Brook Trout
Brook trout (Salvelinus fontinalis) are the only trout native to Maryland.  Arguably the most beautiful freshwater fish, brook trout survive in only the coldest and cleanest water.  As a result, they are good indicators of stream health.  While populations have vanished from many of Maryland’s streams they still survive in a few watersheds – Prettyboy among them.  To ensure their numbers no longer continue to decline, PWA is actively supporting the ongoing efforts of the Maryland Brook Trout Alliance and Trout Unlimited to protect and conserve this species.