M

90%ile

Figure 8-3 Monthly trends of mean, tenth, and ninetieth percentile streamflow for the Potomac River at Little Falls, Virginia (USGS Gage 01646500), 1951-1980. Source: USGS, 1999.

POPULATION, WATER, AND LAND USE TRENDS

In 1996, more than 4.5 million people lived in the Washington, DC, metropolitan area in the vicinity of the tidal river. The Potomac estuary case study area includes a number of counties identified by the Office of Management and Budget as Metropolitan Statistical Areas (MSAs) or Primary Metropolitan Statistical Areas (PMSAs). Table 8-1 lists the MSAs and counties included in this case study. Figure 8-5 presents long-term population trends (1940-1996) for the counties listed in Table 8-1. From 1940

Figure 8-4 Long-term trends in mean, tenth, and ninetieth percentile streamflow in summer (July-September) for the Potomac River at Little Falls, Virginia (USGS Gage 01646500). Source: USGS, 1999.

TABLE 8-1 Metropolitan Statistical Area (MSAs) and

Counties and Incorporated Cities in the Potomac

Estuary Case Study

Calvert County, MD Charles County, MD Frederick County, MD Montgomery County, MD Prince George's County, MD Arlington County, VA Clarke County, VA Culpepper County, VA Fairfax County, VA Fauquier County, VA King George County, VA Loudoun County, VA Prince William County, VA Spotsylvania County, VA Stafford County, VA Warren County, VA Alexandria City, VA Fairfax City, VA Falls Church City, VA Fredericksburg City, VA Manassas City, VA Manassas Park City, VA Berkeley County, WV Jefferson County, WV

Source: OMB, 1999.

Figure 8-5 Long-term trends in population of Washington, DC, metropolitan area. Sources: Forstall, 1995; USDOC, 1998.

to 1996, the population in the Potomac estuary study area nearly quadrupled (Forstall, 1995; USDOC, 1998).

Within the Potomac basin, land use is characterized as forested (55 percent), agricultural (40 percent), and urban (5 percent) (Jaworski, 1990). A rapid transition from agricultural land use to suburban land use has occurred since the 1960s in the Washington, DC, metropolitan area. In contrast to other major metropolitan areas, industrial activities are a negligible component of the regional economy (and wastewater loading). Upstream of the fall line, the free-flowing Potomac is used for five municipal water supply diversions with a total mean withdrawal (ca. 1986) of 386 mgd (MWCOG, 1989). As a result of major improvements in water quality over the past decade, boating and recreational and commercial fishing have become important resource uses of the Potomac estuary.

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