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  Landscape Characterization / Impervious Surfaces / What are the effects? / Water quality

What are the effects?
Quality Impacts

Polluted runoff from impervious urban surfaces, commonly referred to as urban nonpoint source pollution, causes serious local water quality problems. The contributions of nonpoint source pollution to poor water quality become more apparent as point source discharges are reduced or eliminated.


Trajectory of Polluted Water

Set 1

Set 2
 
 
  Into the Chesapeake Bay

Point sources of water pollution are locations where specific pollutants are discharged directly into lakes, streams, estuaries, and coastal waters via pipes and other discernable conduits. Point sources include industries, power plants, and sewage treatment facilities.

Nonpoint source pollution is generated from broad land areas, and pollutants are delivered to water bodies via stormwater and snowmelt runoff. This type of pollution contaminates both surface water and groundwater resources. It generally takes several runoff events to transport pollutants from their sources to receiving waters.

Impervious Surfaces...

Source: NEMO

  • Are indicators of intensive land uses that cause pollution
  • Inhibit recharge of groundwater
  • prevent natural processing of pollutants in soil and plants
  • provide a surface for accumulation of pollutants
  • provide an express route for pollutants to waterways

How Development Impacts Water Quality

 

  • Nutrients

  • Pathogens

  • Sediment

  • Toxic Contaminants

  • Debris

  • Thermal Stress

    

Source: NEMO

Nutrients
Nutrients such as nitrogen and phosphorus are substances needed for plant growth, but elevated levels can cause a health hazard in drinking water and stimulate excessive aquatic plant growth, which can ultimately lower dissolved oxygen levels.
Sources: animal waste, fertilizers, septic systems, auto emissions.

Sediment
 Sediment is eroded soil or sand that smothers aquatic habitat, carries pollutants, and reduces water clarity.
Sources: road sand, construction sites, agricultural fields, disturbed areas.

Debris
Debris includes plastics and other trash that threaten aquatic life and reduce recreational and aesthetic value.
Sources: illegal dumping, street litter, beach litter, boating waste.

Pathogens
Pathogens are disease-causing bacteria and viruses associated with the presence of fecal matter and can lead to shellfish bed and beach closures.
Sources: failling septic systems, animal waste, marine sanitation devices.

Toxic Contaminants
Toxic contaminants are compounds like heavy metals and pesticides that can threaten the health of both aquatic and human life, and are often resistant to decomposition. Sources: industrial, commercial, household and agricultural chemicals; auto emissions.

Thermal Stress
Thermal stress is an elevation in water temperature that can harm native species of plants and animals while helping nonnative species to spread.
Sources: runoff from heat-absorbing impervious surfaces, removal of streamside vegetation, shallow water impoundments,
decreased base flow.

Want to learn more about nonpoint source pollution? How about your local watershed? If so, give these sites a visit.

NEMO - Nonpoint Education For Municipal Officials, a University of Connecticut Cooperative Extension Program.
http://nemo.uconn.edu/

EPA Office of Water: Nonpoint Source Pollution Program
www.epa.gov/OWOW/NPS

Nonpoint Source Pollution: The Nation's Largest Water Quality Problem
http://www.epa.gov/owow/NPS

Enforceable State Mechanisms For The Control of Nonpoint Source Water Pollution
www.epa.gov/owow/nps/elistudy/

Nonpoint Source Pollution: Water Primer
www.ag.ohio-state.edu/~ohioline/aex-fact/0465.html

EPA's Surf Your Watershed
http://www.epa.gov/surf/

 

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