Glossary
Erosion
The process by which natural forces like water, wind, or ice wear away and transport soil and rock.
Example:
Deforestation on steep slopes can significantly increase soil erosion, leading to sediment buildup in rivers and reservoirs.
Headwaters
The source or starting point of a river or stream within a watershed, typically found at higher elevations.
Example:
The clear, cold springs high in the Rocky Mountains serve as the headwaters for many major rivers in the western United States.
Infiltration
The process by which water on the ground surface enters the soil, moving downward through the soil layers.
Example:
Healthy forest soils with abundant organic matter promote high rates of infiltration, replenishing groundwater supplies.
Length (of a watershed)
The distance from the headwaters to the discharge point of a watershed, influencing the time it takes for water to travel through the system.
Example:
A longer length of a watershed means that pollutants introduced upstream will take more time to reach the main body of water, potentially allowing for natural attenuation.
Runoff
Water from precipitation or irrigation that flows over the land surface rather than infiltrating the soil.
Example:
After a heavy rain, the excess water that doesn't soak into the ground becomes runoff, carrying sediments and pollutants into streams.
Size (of a watershed)
The total land area encompassed by a watershed, which dictates the volume of water it can collect and discharge.
Example:
A larger size of a watershed often correlates with a greater potential for flooding during heavy rainfall due to the vast amount of collected water.
Slope (of a watershed)
The steepness of the land within a watershed, which directly affects the speed of water runoff and the potential for erosion.
Example:
A steep slope in a mountainous watershed can lead to rapid runoff and flash floods, especially after intense storms.
Soil type (in a watershed)
The composition of the soil within a watershed, determining its capacity for water absorption (infiltration) and retention.
Example:
Sandy soil type allows for high infiltration rates, quickly absorbing rainwater, while clay soils tend to cause more surface runoff.
Sub-watersheds
Smaller drainage areas within a larger watershed, where water collects and flows into a larger stream or river before reaching the main outlet.
Example:
A large river basin might contain several distinct sub-watersheds, each contributing water from its own network of smaller creeks and streams.
Vegetation (in a watershed)
The plant cover within a watershed, crucial for stabilizing soil, reducing erosion, promoting infiltration, and filtering pollutants.
Example:
Dense forest vegetation along a riverbank helps prevent soil erosion by holding the soil in place with its root systems.
Water quality
The chemical, physical, and biological characteristics of water, indicating its suitability for a particular purpose or ecosystem health.
Example:
Pollution from agricultural fertilizers can degrade the water quality of a watershed, leading to algal blooms and reduced oxygen levels.
Watershed
An area of land that channels all precipitation and runoff to a common outlet, such as a river, lake, or ocean.
Example:
The Mississippi River watershed is one of the largest in the world, draining water from over 30 U.S. states into the Gulf of Mexico.