TABLE 1.

Land uses in the Potomac River basin upstream of the five sampling sites

Land use and contamination sourceAcres (%)a
Monocacy RiverNorth Fork Shenandoah RiverGreat Seneca CreekCorbalis WTP and Potomac WFPb
Total area447,397415,7916,2187,286,006
Residential9,359 (2.1)8,238 (2.0)1,521 (24.5)141,047 (1.9)
Commercial/industrial103 (0)434 (0.1)243 (3.9)111,123 (1.5)
Agricultural pasture/hay194,291 (43.4)126,423 (30.4)176 (2.8)1,742,238 (23.9)
Agricultural crop93,192 (20.8)11,522 (2.8)1,127 (18.1)773,018 (10.6)
Park/grass15,718 (3.5)17,911 (4.3)118 (1.9)4,363 (0.1)
Forest/woods119,012 (26.6)250,022 (60.1)2,911 (46.8)4,391,526 (60.3)
Water/wetland11,049 (2.5)1,041 (0.3)11 (0.2)88,055 (1.2)
Other4,673 (1.0)200 (0.1)1 (0)34,617 (0.5)
  • a Determined by geographic information system mapping. The potential sources of contamination are as follows: for the Monocacy River, Corbalis WTP, and Potomac WFP, agricultural and wastewater discharge; for the North Fork Shenandoah River, agricultural; and for the Great Seneca Creek, wastewater discharge.

  • b The data are data for the Potomac WFP site, but the data for the Corbalis WTP site would be similar, as the latter is only 6 miles upstream on the Potomac River, into which the Monocacy River, North Fork Shenandoah River, and Great Seneca Creek watersheds all drain. The Corbalis WTP site, however, is not believed to be influenced by the Great Seneca Creek discharge.