Lake Manassas Dam (creating a reservoir on Broad Run at Glenkirk Road)
As described by the Metropolitan Washington Council of Governments, "The Washington metropolitan region gets nearly 90% of its drinking water from the Potomac River. Its supply is further augmented by water from the Jennings Randolph and Little Seneca Reservoirs, the Patuxent and Occoquan rivers, Goose Creek (a Potomac Tributary), Lake Manassas (which feeds the Occoquan), and groundwater resources."
Several Northern Virginia jurisdictions have separate systems for storing, treating, and delivering drinking water to their citizens - not everyone relies upon the same system. Arlington County gets its water from the Potomac River, using the same system that provides water to DC (which has had water quality issues with excessive lead levels). The Washington Aqueduct Division of the Army Corps of Engineers diverts Potomac River water at Great Falls and at Little Falls, before the river reaches sea leve and fresh water is mixed with salt water.
The City of Alexandria, on the other hand, gets its water from the Occoquan Reservoir. That water is drawn out of the Occoquan River before it joins the Potomac River, so it too is fresh. It's "used" water, however. A high percentage of the water in Bull Run and the reservoir, especially in the summer, has been processed upsteam through the Upper Occoquan Sewage Authority wastewater treatment plant. When you turn the tap in houses in southern Fairfax County, eastern Prince William, and Alexandria, you will be drinking re-processed sewage from Centreville. (Of course, people drinking water from the Potomac River are getting some reprocessed sewage from places upstream - Harpers Ferry in West Virginia, Cumberland in Maryland, and all of the urbanized areas in the Shenandoah Valley of Virginia south to Staunton.
The City of Fairfax, when it incorporated and became independent from the County of Fairfax almost 50 years ago, made sure that it had a separate water supply at Goose Creek Reservoir and Beaverdam Creek in Loudoun County. If the city had been dependent upon the county for water, then the county would have had great leverage to limit the potential growth of the city.
The City of Manassas owns Lake Manassas. It is located in Prince William County - the city owns the lake and much of the adjacent shoreline, but the property is still in the jurisdiction of Prince William County. All the rainfall that flows into Lake Manasas comes from Fauquier and Prince William - not a drop of water in the reservoir comes from the city. However, the city won't let county residents go fishing or boating on the reservoir.
Fairfax County did play hardball in those days. It even acquired through eminent domain the water supply of Alexandria in the 1960's. Fairfax County could not seize property of a fellow local government - but it could condemn the private Alexandria Water Company that had built the Occoquan Reservoir and was selling water to Alexandria. After paying fair market value, as required by the Fifth Amendment, Fairfax County seized control of the reservoir and water system that even today supplies Alexandria and much of eastern Prince William County.
However, water flows by gravity. Even competing jurisdictions prefer to "partner" in order to provide water in some watersheds rather than build pumping stations and duplicate pipes. To see what sources supply different jurisdictions in Northern Virginia, see:
However, there are limits to cooperation. The City of Falls Church has been buying drinking water from the County of Fairfax at wholesale rates, then charging customers a much higher retail rate. Fairfax County recently decided to compete for those customers, breaking an informal understanding that separate jurisdictions would service different areas. Read:
All cities and counties have linked their systems together now, and agreed on a water-sharing plan. This cooperation was spurred in part by a severe drought in 1966, then another one in 1978 and a more-recent drought in 2002. You can see the relatively low flow at Goose Creek near Leesburg in 2002 compared to other years, as measured by USGS:
| Water Year | 00060, Discharge, cubic feet per second |
|---|---|
| 2001 | 231.4 |
| 2002 | 80.0 |
| 2003 | 811.5 |
| 2004 | 526.5 |
| 2005 | 404.2 |
| 2006 | 248.0 |
| 2007 | 305.7 |
The independently-elected politicians may be pushed to make a regional investment in new infrastructure, such as new dams and reservoirs, to supply the projected increase in population. A state-mandated water supply study will be completed by 2011. It may call for conservation, but the potential of proposing new storage sites is also possible.
If so, the recommendations won't be new. A 1999 report by the League of Women Voters in Fairfax County considered building new water reservoirs far upstream in the Shenandoah and Potomac River watersheds, as well as a dam on the main stem of the Potomac River at Seneca Creek (upstream of Great Falls). One possibility was to build a dam on a small creek near the Potomac River, then pump water out of the main river during high-flow seasons and withdraw the water during droughts.
However, the report noted "There has been widespread development both in the valleys that would be flooded and along potential shorelines in much of the basin. In more remote areas, there would be intense opposition to impounding free-flowing streams in scenic areas." There are no empty spaces upstream of Washington, DC where land could be flooded and no one would care.
Read: