A golf course can probably be built and operated without serious damage to the aquatic environment, although many result in negative impacts. The cumulative impacts of Prince William's many golf courses are largely unknown and, because two-thirds of Prince William lies in the Occoquan Watershed, of special concern. The Occoquan Land Use survey shows that in 2000 there were 2060 acres of golf courses in the Occoquan Watershed. Fifty-two percent of these acres are in Prince William, which represents about 40% of the total watershed area.

The effect of a golf course on water quality is comparable that of an area developed with half-acre houses, which is about 25% impervious surface. Within a small watershed, when more than 50% of the total acres are golf courses the result is moderate to severe degradation of water quality - waterways that are not suitable for drinking, swimming or fishing.

Golf courses impact both surface and groundwater. The groundwater supply in western Prince William, where additional golf courses are planned, is regulated by the underground rock structure, soil type, rainfall amount, lay of the land and ground cover. Prince William's groundwater supply is heavily dependent on rainfall because of land structure. During dry weather and periods of drought, the inflow of water to nontidal wetlands and streams comes from groundwater. The volume of this inflow, which is dependent on the groundwater supply, affects the water quality of surface waters in the Occoquan reservoir watershed. In addition, a majority of western Prince William residents depend on groundwater for their drinking water supply.

No comprehensive groundwater study for Prince William County has occurred for nearly 20 years. The Prince William County groundwater study required by the 1998 Comprehensive Plan has been deferred to an undetermined date. Studies completed for individual golf courses do not address cumulative impacts at any scale. Existing studies that focus solely on the recharge rate for specific golf courses are incomplete and of limited value.

A Maryland study shows that on average 23% of the annual rainfall (43 inches) will soak into the ground. This is equivalent to one quarter-million gallons of groundwater recharge per acre per year. EPA studies show that conversion of forested land to managed turfgrass decreases the amount of water that soaks into the ground by 15%. Golf courses also bring additional homes and community facilities to nearby acres. The groundwater recharge rate for areas converted to parking lots, roads, clubhouses and houses is reduced by 100%.

The quantity of fertilizers applied to turfgrass is about the same as that used on cropland. The potential for these to leach to groundwater is high. Nitrogen (nitrates) is of special concern. An average of 5 - 10% of nitrogen fertilizers leaches to groundwater, and up to 84% can infiltrate to groundwater. Golf course grass is mowed to short heights, which attracts many pests. Groundskeepers use preventative strategies, which results in the regular use of a variety of pesticides. The Integrated Pest Management control strategies used by many golf courses reduce pesticide use by 50%. But golf courses still use three to four times the amount of pesticides as cropfields. Birds and other wildlife are frequent victims of turfgrass pesticides.

What are the additional impacts when accidents occur? Accidents involving golf course chemicals can result in serious degradation of ground and surface water. A recent accident involving pesticides at an Arlington County golf course resulted in the rapid demise of all living organisms in Donaldson Run. The value lost in habitat is compounded by costs incurred to mitigate the damage.

Golf courses in western Prince William will use large quantities of groundwater. The Virginia State Water Control Board's 1986 statistics show that golf courses use an average of 27,000 to 223,000 gallons of water per day over the course on a year. A Maryland study shows that an 18-hole golf course in the metropolitan D.C. area uses 100,000 to 150,000 gallons per day. As little as 10% of this water filters back into the ground: virtually all the water evapotranspirates into the atmosphere.

This covers some, but not all, of the environmental impacts that could result from unchecked golf course development in Prince William. It is clear that land use impacts to the water supply in the Occoquan Watershed cannot be disregarded. These impacts would affect the current Prince William residents with wells and the 1.2 million Northern Virginia residents who rely on the Occoquan Reservoir for their drinking water.