Humans and plants depend on an adequate supply of clean water for a number of reasons, from producingfood to sustaining life. The average Virginia resident uses 826 gallons of fresh water daily (Virginia Department of Environmental Quality [VADEQ] 2008). In the Commonwealth alone, there are more than one million households that depend on well water, withdrawing more than 50 billion gallons annually (Virginia Department of Health 2008). For groundwater replenishment, we depend largely on recharge (water moving from the surface to groundwater) from infiltration of precipitation through permeable surfaces in the environment — an important part of the natural water cycle (VADEQ 2010).

A dry swale (DS) is a shallow, gently sloping channel with broad, vegetated, side slopes. Water flow is slowed by a series of check dams (see figure 1). A DS provides temporary storage, filtration, and infiltration of stormwater runoff. Dry swales function similarly to bioretention, and are comparable to wet swales; however, unlike a wet swale, a DS should remain dry during periods of no rainfall. A DS is an engineered best management practice (BMP) that is designed to reduce pollution through runoff reduction and pollutant removal and is part of a site’s stormwater treatment practice (see figure 2).

A wet swale (WS) is an engineered, best management practice (BMP) arranged in a straight line that is designed to reduce stormwater pollution. A WS consists of a shallow, gently sloping channel with broad, vegetated, side slopes and slow flows (see figure 1). Wet swales typically stay wet because the bottom of the swale is below the water table. This is done to encourage the growth of wetland vegetation, providing water quality treatment similar to a natural wetland. This stormwater treatment practice also functions as part of the stormwater conveyance system. Wet swales have a relatively low capital cost; however, maintenance can be is intensive and expensive when compared to other BMPs.

A stormwater filtering practice (FP) treats stormwater runoff by passing it through an engineered filter media consisting of either sand, gravel, organic matter, and/ or a proprietary manufactured product, collecting it in an underdrain, and then discharging the effluent to a stormwater conveyance system. FPs are stormwater treatment practices that are often obtained from the marketplace due to unique proprietary technologies (see figure 1).

Greywater is any household wastewater other than that used for toilet flushing. This water could be reused around the home (for purposes other than drinking water). An example of greywater use is landscape irrigation. Wastewater that comes in contact with human waste is referred to as blackwater. However, the definition of greywater varies according to state regulations.

Reclaimed water, sometimes referred to as “water reuse” or “recycled water,” is water recovered from domestic, municipal, or industrial wastewater treatment plants that has been treated to standards that allow it to be safely used for designated purposes. Reclaimed water should not be confused with “wastewater,” untreated liquid industrial waste or domestic sewage. However, “gray water,” untreated water from bathing or washing, is considered one form of wastewater (Water Reuse, VCE Publication 452-014). The level of treatment and disinfection reclaimed water receives is dictated by its intended (and permitted) use. Many states encourage and promote the use of reclaimed water to conserve freshwater supplies and preserve rivers, streams, lakes, and aquifers.

Rainwater harvesting is the process of collecting, storing, and later reusing rainwater from surfaces such as roofs. Rainwater harvesting has long been used for agricultural irrigation and as a source of drinking water, and allowed ancient civilizations to flourish in semi-arid and arid regions. Rainwater harvesting systems are in use today in many water-limited locations, especially in several western US regions. As population growth increases pressure on water resources in the more humid eastern US, rainwater harvesting is being considered to reduce the demand for potable water.

This fact sheet presents and explains some common concepts in hydrology and the hydrologic cycle. The science or study of hydrology focuses on the distribution, occurrence, circulation, and properties of water in the environment.