The Opal Creek Valley contains 50 waterfalls, 5 lakes and 36 miles of hiking trails. It forms the largest intact stand of old growth forest in the Western Cascades and 500-1000 year old trees are common. The most abundant trees are Douglas fir, Western Red cedar and Western Hemlock. Source: WSF
Water. Essential to survival, yet too much is destructive. And not enough, a crisis.
While water wars in many nations are commonplace due to scarcity, other regions represent water utopia. Early Europeans spoke of the clean and plentiful water in the New World – what would become the United States’ eastern seaboard. And while that has been the case in the mid-west and eastern U.S., it might not always be that way.
Increased populations, technologies and higher per-capita demands place pressure on water resources. Intensified demand, coupled with continued land-use changes, means fighting over water may be the headlines of tomorrow. Watershed management can help avoid this crisis.
Watershed management
Edge of a pond with a variety of deciduous and evergreen trees growing on the shoreline. Source: WSF
According to The Dictionary of Forestry a watershed is, “a region or land area drained by a single stream, river, or drainage network.” Every parcel of land is part of a larger geographically defined area called a watershed. A watershed is simply an area that has one thing in common: the point to which it drains. An area within a given watershed may include parking lots, buildings, roads, sub-divisions, agricultural fields, forests and any other land use, and the value of the watershed is related directly to these end uses.
Even the tiniest morsel of watershed may drain into a small seasonal creek, which is sometimes dry. This is an “intermittent stream,” and in most cases, it will empty into a perennial stream (containing water year around). An even larger watershed would be drained by a river into which many perennial and intermittent streams empty, and so on.
Runoff from pavements, industry and housing can wreak havoc on the watershed, when there’s no buffer in place. Photo: Betsy Crowfoot
As a rule of thumb, the type and volume of land use can impact the watershed’s ability to produce sufficient clean water. For example, runoff from a parking lot typically carries many pollutants left behind from automobiles. Agricultural lands may introduce pollutants to waterways depending on management practices (such as the use of excessive fertilizers) or soil erosion (if conventional tillage is practiced up to, or near, stream edges). Lawns are another significant source of water pollution (over fertilization, and the use of herbicides or pesticides) when there’s little or no buffer between the turf and the waterway. Whenever pollutants are in close proximity to a body of water – even a simple stream – water quality is compromised.
The costs of diminished water quality trickles down to everyone. Municipalities collecting water from an unhealthy watershed are faced with costly processes to make water potable again. Fish and other aquatic organisms dependent on water habitats suffer also. As some of these natural ecosystem components are lost or damaged, the problem compounds.
Go with the flow
Edge of a pond with a variety of deciduous and evergreen trees growing on the shoreline. Source: WSF
Ecosystems dominated by natural habitats clean water as part of their inherent processes, and forests are the most productive element of a watershed. A typical forest, hydrologically speaking, is a filter and a sponge. As rain falls on a forest, the layer of leaf littering the ground soaks up the water, and holds it in place so it doesn’t run off. Slowly (perhaps over the course of many days) the water is released, recharging ground and surface water supplies. As this water is slowly rendered, soil particles, organisms and organic matter filter out most impurities.
Water coming from forested watersheds is the cleanest water available – without any human intervention. Additionally, ground water and stream levels from a forested watershed are more constant, and the risk of catastrophic flooding downstream is diminished. While these are best for water quality and quantity, they are not always feasible – especially on the larger scale. However, some of the benefits forests provide over a whole watershed can be realized on a small but important part of the watershed as well.
Riparian Buffers: the hub of a watershed
An important element of a healthy watershed lies next to the water. Certain plant communities are very effective at buffering the potential negatives of adjoining land use. Riparian buffers are the areas along the bank which help safeguard the water from potential pollutants. Sediment, nutrients and impurities headed toward a body of water can be trapped and stored in this plant matter, absorbed onto soil particles, or modified by soil organisms. Too abrupt a change from a stream to a lawn or driveway can prove a liability in terms of water quality and even quantity.
So what does a riparian buffer look like?
A riparian zone after restoration. Source: Virginia Department of Inland Game and Fisheries
Most buffers are low maintenance areas, linear in shape and a certain width beyond water edge. There is some controversy as to what kind of vegetation is best. Grass, shrubs and trees can all function as a buffer, but in general, a mixture of these plant communities, much like a gradual edge for wildlife, is good.
How wide a buffer is one of the first dilemmas. In the instance of a small acreage owner, the barrier is likely to be limited to the space available. In general, the minimum width for a buffer is roughly 20 feet, to meet bank stabilization, nutrient removal, flood control, and wildlife habitat goals. Other factors to consider include soil type and stream size. Finer soils and larger streams call for wider buffers. In general the rule of thumb is ‘the wider, the better’ – however something is better than nothing.
For the private homeowner, establishing a buffer might involve nothing more than to stop mowing. In other cases, the addition of trees, shrubs and native grasses is advised. In situations where a stream is cutting under the bank, causing the embankment to collapse, it may be prudent to initially stabilize the shore with various materials and methods such as rock riprap, or live stakes from tree and shrub cuttings.
In addition to keeping waters clean, forested buffers keep water cool. Cooler waters have higher oxygen contents, healthier macro-invertebrate populations and are more likely to support native fish populations as well.
Many of these unique and vital ecological areas are in the hands of private landowners, who have an opportunity and responsibility to ensure the well-being of the watershed by maintaining an adequate riparian buffer. For more information read the Understanding the Science Behind Riparian Forest Buffer series available from the Virginia Polytechnic Institute and State University Cooperative Extension.
Adam Downing is a faculty member of Virginia Tech, and has worked as the Natural Resources Extension Agent serving Virginia Cooperative Extension’s Northern District, a 19 county area generally described as the Northern Piedmont of Virginia. His professional expertise is in providing informal educational regarding forestry and natural resources to address current issues in rural, urban, and rural/urban interface areas to home & landowners, professionals, decision-makers, and the general public. His mission is to enable people to make best decisions regarding the forest & natural resources, within their realm of influence, resulting in environmentally sustainable management, growth, and quality of life for that person and that community.
