Updated: Feb 23, 2020
A ridge dividing the areas drained by different river systems.
The area drained by a river system.
Webster’s New World Dictionary of the American Language, 1964
More than 70 percent of the Earth’s surface is covered with water and the natural water cycle provides water to Earth as a recyclable resource. However, Earth’s water supply is not infinite, nor is it infinitely renewable. A powerful graphic on the United State Geological Survey (USGS) website shows how small the volume of water on Earth truly is. In this image, all water on, in, and above the Earth is represented as a sphere. The sphere is not large in comparison to the planet, with a diameter running roughly the distance from Utah to Kentucky. A much smaller sphere represents the volume of all fresh water on Earth. And a tiny sphere represents all of the fresh water in rivers and lakes on the planet. This tiny sphere is the water that sustains us and most of the other life on the planet. You can see this graphic here. This imagery underscores that water is a precious resource. Our local watersheds provide us with the greatest opportunity as individuals to preserve and protect this resource.
The definition of watershed above comes from a dictionary that, as of this writing, is 52 years old. More current dictionaries also include a secondary definition: a time when an important change or event occurs. With rapidly increasing populations creating challenges for meeting and managing urban and agricultural needs, we are facing a watershed moment in protecting and restoring watershed health.
Human factors adversely affecting the volume and quality of water in a watershed include:
Creation of impervious land cover, such as parking lots and roads, which inhibit infiltration into the soil, increase incidents of flooding, and decrease water quality.
Consumptive use that reduces, and in some cases eliminates, evapotranspiration (Medellín-Azuara, Kyaw, Yufang, Lund, Hart, Kent, Clay, Wong, Leinfelder-Miles, 2015).
Extraction and consumptive use creating drought conditions leading to collapse of river and estuary ecosystems (Rosenfeld, 2016).
Contaminated run-off from pesticide and herbicide application and chemical lawn fertilizers (Schueler, 2000).
Restoring and protecting watershed health makes sense environmentally, ethically, and economically. Healthy watersheds provide protection from erosion and flooding. Development costs for best management practices (BMPs) protective of watershed health do not increase construction costs while increasing property values (Schueler, 2000). Economic benefit is also derived from protected areas unavailable for land development. Undeveloped areas that provide habitats for wildlife also support recreation such as hunting, fishing, birdwatching and hiking. The State of New Jersey has estimated the value of freshwater wetland services at 9.4 billion dollars per year (Mates, 2007).
Changes in individual behavior can improve watershed health. The increase in household recycling and decreases in littering and oil dumping in the past few decades indicate that environmentally protective changes in behavior can be adopted and normalized. Actions that reduce run-off and actions that reduce the amount of contaminants introduced into the runoff can increase water quality and encourage natural infiltration, which helps protect local watersheds. Conserving and re-using household water where feasible is a good way for individuals to protect the local watershed.
Some other actions individuals can take include:
Applying no fertilizer to lawn and/or ensuring chemical fertilizers applied do not contain pesticides and herbicides.
Applying pesticides and herbicides to yards and outdoor areas only as a last resort.
Inspecting septic systems and pumping them out when needed.
Replacing non-native plant cover, such as turf lawns with native fauna, including trees.
The last bullet brings us to urban watershed forestry, which among other benefits, offers an opportunity for municipalities, developers, and individuals to embrace BMPs that protect and increase the quality of local watersheds. The United States Division of Agriculture (USDA) Forest Service has been working to increase general knowledge on the benefits of urban watershed forestry.
Some benefits of trees to the watershed include:
Reduction of contaminated run-off through evaporation from the canopy, water uptake through tree roots, and increased soil-drainage in the root zone.
Absorption of pollutants such as carbon monoxide and particulate matter.
Reduction of air temperature, reducing formation of pollutants and indirectly decreasing energy use by surrounding households.
More benefits and more details regarding urban watershed forestry can be found at the Center for Watershed Protection and US Forest Service. The US Forest Service also provides guidance to planting trees on residential lawns. Information regarding the many other benefits of urban forestry can be explored at the USDA Forest Service Urban and Community Forestry Program site.
References & Resources
2016, California WaterBlog, Comparing Delta Consumptive Use preliminary Results from a Blind Model Comparison, October.
2016, Center for Watershed Protection, Urban Watershed Forestry, -.
2016, Center for Watershed Protection, Watershed Science Bulletin, -.
2016, SFGATE, SF Bay ecosystem collapsing as rivers diverted, scientists report, October.
2016, United States Department of Agriculture (USDA) Forest Service, Urban and Community Forest Program, -.
2016, Unites States Geological Survey (USGS), What is a watershed?, October.
2015, Medellín-Azuara, Kyaw, Yufang, Lund, Hart, Kent, Clay, Wong, Leinfelder-Miles, Delta Consumptive Water Use Comparative Study, -.
2013, Colorado Conservation Board, Agricultural Economic and Water Resources: Methods, Metrics and Models – A Specialty Workshop, July.
2007, Center for Watershed Protection, Watershed Forestry Resource Guide, -.
2000, Claytor, Assessing the Potential for Urban Watershed Restoration: The Practice of Watershed Protection, -.
2000, Schueler, The Economics of Watershed Protection, -.
2000, Schueler, On Watershed Education: The Practice of Watershed Protection, -.
2000, Schueler, Watershed Protection Techniques: Understanding Watershed Behavior