Principle of Watershed Management
Essay title: Principle of Watershed Management
Principle of Watershed Management
Watershed management approaches are evolving throughout the country and are being used to address watersheds that have multiple problems. Based on successful watershed management efforts like these across the country, this tutorial presents four core principles of watershed management:
Watersheds are natural systems that we can work with.
Watershed management is continuous and needs a multi-disciplinary approach.
A watershed management framework supports partnering, using sound science, taking well-planned actions and achieving results.
A flexible approach is always needed.
Principle 1
a. Delineating the Watershed
A watershed is simply the land that water flows across or through on its way to a common stream, river, or lake. A watershed can be very large (e.g. draining thousands of square miles to a major river or lake or the ocean), or very small, such as a 20-acre watershed that drains to a pond. A small watershed that nests inside of a larger watershed is sometimes referred to as a sub watershed.
You can delineate a watershed (or many watersheds) on topographic (topo) maps using symbols for important entities: lines symbolizing water and elevation contour lines indicating areas of equal height above sea level. Since water flows downhill from higher elevations to a common body of water, to delineate the watershed boundary for a particular place on a stream or lake, you will need to draw a line along the ridgetops connecting the highest elevation points surrounding the lake or stream. Fortunately, there are maps and computer databases you can turn to that have watershed boundaries already delineated–particularly for larger basins and watersheds. What pops up is the watershed boundary with major streams, lakes and cities in the watershed highlighted. Some experts like to categorize the hydrography or water bodies within a watershed by a classification system referred to as stream order. For example, when a stream first begins, it is called a first order stream. When two first-order streams join, the water below the junction is called a second order stream, etc. In this classification system, the next higher order stream is formed when two of the immediately lower order streams have joined. We often talk about three management zones when discussing watershed management–the waterbody, riparian, and upland zones. Waterbody is a term that includes any stream, river, pond, lake, estuary or ocean. The riparian zone is defined as the non-cultivated, vegetated area between the waterbody edge and the upland area. Riparian means “of the river” and the riparian zone is intimately connected with the waterbody. This zone often includes, but is not limited to, wetlands bordering waterbodies. The upland area is not an exact term, but usually is defined as the land above a high water mark (e.g. 100 year flood plain).
b. Natural Processes at Work in the Watershed
Importantly, no matter where we live or work, we are in a watershed teeming with unique, inter-related natural processes. These natural forces help shape the watershed landscape, its water quality, and–in turn–our lives.
In mountain upland areas, there are unique blends of climate, geology, hydrology, soils, and vegetation shaping the landscape, with waterways often cutting down steep slopes. Look closely at this picture and the many things that influence water quality: chemicals from the mineral weathering of rocks, from the decay of vegetation, and from groundwater. Notice how the vegetation shades the water, influencing temperature and what can live in the water.
In an upland plains area, you find grassy plains, hardy vegetation, and slower moving, meandering streams and rivers.
In the coastal area, where oceans meet land, there are again different blends of features and processes shaping the environment.
In lowland areas between upland and coastal waters, where tidal wetlands are prevalent, processes serve entirely different functions.
In other words, each watershed–indeed each watershed zone–has unique living and nonliving components that interact, with one element responding to the action or change of another. Knowing your watershed means coming to learn the natural processes working within the watershed boundaries.
Once you better understand these processes, you can better appreciate how the watersheds ecological processes help sustain life. For example, a healthy watershed provides habitat for fish and other