Green Scene Blog: How’s the water?


Folks–this post is from the director of StreamWatch. Rose Brown explains what the heck exurban means, and what it means to water health.

The nonprofit I run, StreamWatch, recently released its latest study, which examined the relationships between how we use our land and stream health in the Rivanna River watershed.

A watershed is an area of land that drains to a stream. The rain that falls on your roof will eventually run to a stream;you live within the watershed of that stream. Small streams flow into larger streams, so smaller watersheds are nested within larger watersheds. If you are standing on the downtown mall, you are in the Moores Creek watershed, which is part of the Rivanna watershed, which is part of the James River watershed, which is part of the Chesapeake Bay watershed. This is called your watershed address.

Stream health is very closely related to land use in the surrounding watershed. Rural landscapes with lots of forest have healthy streams. Forested buffers alongside streams can protect and improve stream health. Unstable stream banks and excess sediment cause stream health to decline in many Rivanna streams. Urban areas with lots of paved surfaces have unhealthy streams. The relationship between land use and stream health is so strong that we can estimate stream health based on the amount of forest and development in the surrounding watershed.

About 70 percent of streams in the Rivanna watershed are failing Virginia’s biological standard, a marker of whether streams support a variety of life forms. Streams with more life have better water quality, and can provide better services to humans—like water supply, recreation, and aesthetic enjoyment.

Most of the Rivanna watershed is exurban (or semi-rural). Exurban areas are more populated than rural areas, but less than suburbs. In our exurban landscapes, about 70 percent of the land is forested, and each property is an average of 17 acres. This amount of land disturbance may seem mild, but more than half of exurban streams failed the biological standard.

Rural and exurban streams decline rapidly with increased development or deforestation. In urban areas, stream health is already poor. Therefore, urban streams do not respond dramatically to additional development. Based on current development practices and projected land use changes, a third of our remaining healthy streams could fail the standard within 20 years.

Fortunately, only 5 percent to 10 percent of streams are severely degraded. Most streams sit near the pass/fail cusp and might meet the standard with better care.

Here’s more information about StreamWatch’s key findings.