Casperkill Watershed Oral History Project

A healthy vs. an unhealthy watershed, image courtesy of http://www.dutchesswatersheds.org.

In the Northeastern United States, healthy watersheds share the same  basic characteristics:

Forested hillslopes, which are important because:

• Trees shade the stream from the sun’s heat in the summer to keep water cool for fish
• Fallen logs provide habitats for fish and other aquatic animals
• Leaves and twigs fall into the channel and provide food for insect larvae, mollusks, and other invertebrates
• Tree roots stabilize streams’ banks and reduce the erosive power of rain
• The surface area of leaves intercepts, slows, and/or prevents rain’s fall to the ground, and slower rainfall means a greater chance for the rain to percolate into the soil’s pore spaces. This leads to groundwater recharge and decreased runoff
• Reduced sediment runoff into streams
• Soil ‘s organic matter traps heavy metal pollutants before they can enter the water

Thriving aquatic and terrestrial ecosystems live there, which means:

• Nitrogen and phosphorus are constantly cycled between soils, vegetation, stream water, and animals — one organism’s waste becomes another’s food
• A variety of habitats exist for aquatic organisms; bacteria and algae are crucial for capturing nutrients from stream water and making those nutrients available to the aquatic food web
• Floodplain wetlands provide spawning grounds for fish, amphibians, and foraging habits for birds
• Wetlands store and infiltrate stormwater to underlying groundwater systems, which reduces runoff and flooding hazards

Unhealthy watersheds lack these essential qualities. They:

Don’t have forested hillslopes, as they have been replaced by pavement, lawns, or unprotected bare soil, so:

• Impervious surfaces (driveways, buildings, sidewalks, and parking lots) prevent rainwater from soaking into the ground
• Storm sewers carry rainfall directly to streams
• A lack of trees increases the total runoff, and increases the speed at which it reaches strema channels
• Filling in wetlands and floodplains for development reduces the ability of the ground to store storm water
• An increased peak discharge means there is a greater frequency of flooding, and an increased velocity gives the stream greater erosive power

The lack of forested hillslopes allows urban toxins to enter the stream channel, which leads to:

• Motor oil, antifreeze, road salt, and other automotive chemicals “shock” sensitive aquatic organisms
• Fertilizer runoff from lawns and sewage from failed septic systems leads to overgrowth of algae that, when it decays, consumes dissolved oxygen
• A lack of trees coupled with hot parking lot runoff during summer months warms water beyond the capacity of some species to survive and prevents essential uptake of excess nutrients supplied by fertilizer applications

This post was adapted from Health of the Casperkill, Dutchess County, New York.