Water Quality and Land Use

Streams and rivers are likely to be healthy when at least 91% of the ground in their watershed remains permeable, allowing soil and plants to filter precipitation.

Land Use and Water Quality
The Effect of Land Use on Water Quality
A Changing Landscape
The Effect of Agriculture on Water Quality
Air Quality’s Effect on Water Quality
How Can Urban and Suburban Areas Improve Water Quality?

Land Use and Water Quality

Forests, wetlands and open ground are vital to the health of waterways, allowing soil and vegetation to filter rainwater before it enters local streams or rivers. This role is so important that in areas where 10% or more of the ground is covered with waterproof surfaces, such as asphalt or rooftops, water quality is likely to be impaired. Streams are likely to be healthy when at least 91% of the ground in their watershed remains permeable.

Forests are particularly beneficial because their trees and other plants can intercept the falling rain, allowing it to evaporate, transpire back into the air, or seep gradually into underground aquifers instead of pouring suddenly into waterways in a rush that can lead to flooding and erosion. Forests along waterways are especially valuable since the plants’ roots help stabilize stream banks. Wetlands are also highly valuable because they store water, and so contain runaway sediment, break down or sequester pollutants, prevent floods and allow groundwater recharge. In both forests and wetlands, dense vegetation processes the water, filtering out contamination.

By contrast, when rain falls onto parking lots, compacted dirt, paved roads or rooftops, it slides quickly over the waterpoof surfaces, picking up pollutants which it carries through curb gutters, storms drains and ditches directly into the nearest waterway. The force of this unnatural deluge erodes stream banks and clogs the already fouled waters with sediment. Parasites and microbes, clinging to suspended soil, further pollute the rushing water.

The Effect of Land Use on Water Quality

Obviously, the more heavily land is used for residential purposes, the more people will demand water. Land uses-ranging from farming and forestry to cities and suburbs-also have a major impact on the available water supply. In a healthy watershed, most rain seeps into open ground before it joins a waterway, or it soaks into wetlands that store it like a sponge, or it falls in a forest where trees raise the water through their branches, releasing it through transpiration. As water rejoins the air, clouds can form and rains come again. In a largely natural landscape, rain not recycled for future clouds can soak into the soil and recharge groundwater supplies which steadily feed streams and rivers. By contrast, hard surfaces tend to channel stormwater rapidly into waterways, dangerously swelling streams and rivers while ushering needed water quickly away from the area. So, intensive development can contribute to a cycle of extremes in our streams- very high flows interspersed with very low flows.

A Changing Landscape

Between 1990 and 2000, over 250,000 acres in the Chesapeake Bay watershed (which includes the Piedmont) were paved or otherwise covered with impervious materials. Countering this alarming trend, PEC has helped to protect an equivalent amount of open space, nearly a quarter million acres in our nine-county region.

In the Piedmont, with our watersheds originating in the Blue Ridge Mountains, we have the opportunity to provide for our own needs, instead of relying on others who may or may not act responsibly. We can attend to the quality and the quantity of the water that we intend to use by stewarding our own landscapes. Meanwhile communities downstream, including the metropolises of Washington and Richmond, rely on water flowing outward from the Piedmont. Many millions of people consume water that flows through this region.

Public drinking supplies are treated, but the processes that aim to filter out contaminants and kill disease-causing organisms are expensive and carry risks. Some chemicals required to disinfect water may react with contaminants, resulting in carcinogenic byproducts. Troublesome microorganisms can elude extermination. And no regulations govern the treatment of pharmaceuticals that appear to be causing reproductive disorders in fish and as yet unknown impacts in humans. Nor do regulations protect people against endocrine disruptors-compounds that can cause reproductive disorders, birth defects, and sexual deformation. By far the most cost-effective and reliable way to provide adequate, clean drinking water is to protect watersheds.

The Effect of Agriculture on Water Quality

Agriculture has drawn attention as a source of water pollution from fertilizers and pesticides, as well as livestock wastes. However, farms’ open ground provides irreplaceable water-filtering services. When farmers take practical steps to protect streams and rivers on their land, they can be excellent stewards of water quality. Virginia’s Conservation Reserve Enhancement Program (CREP) provides funding and support for landowners who improve the health of waterways on their property, through such projects as tree-planting along waterways, fencing cattle away from streams and providing alternative sources of water for livestock. Many farmers and other landowners who donate conservation easements protect streams and rivers by requiring the maintenance of riparian buffers, as part of the easement.

Meanwhile, it is also worth noting that the #1 source of phosphorous found in regional waterways is not farms but fertilized yards, and 30% of nitrogen comes from areas of impervious cover.

Air Quality’s Effect On Water Quality

Contaminants spewed into the air by automobiles, smokestacks and other sources eventually settle or dissolve in the rain, contributing a major portion of the pollution that troubles our waterways. Between 30% and 40% of the nitrogen that chokes life from the Chesapeake Bay can be traced to air pollution. Learn more about Air Quality.

How can Urban and Suburban Areas Improve Water Quality?

Towns, cities and suburbs can make choices that will significantly improve the health of their watersheds. Even in heavily developed areas, people can reduce runoff from impervious surfaces through such innovations as green roofs, permeable pavers, rain barrels and parking lots that drain into rain gardens. Communities can also make a difference by maintaining wooded corridors along streams or rivers and increasing tree cover within the city, town, or suburb.

>> Center for Watershed Protection
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>> Surf Your Watershed (EPA)