Nonpoint Source Pollution (NPS)

Introduction to Nonpoint Source Pollution

Nonpoint source (NPS) pollution refers to diffuse contamination of water that does not originate from a single discrete source. Instead, it comes from many widespread sources, often carried into water bodies by rainfall or snowmelt moving over and through the ground. NPS pollution is a major environmental concern, especially in urban and suburban areas.

• Definition: NPS pollution is pollution resulting from many diffuse sources, as opposed to point source pollution, which comes from a single, identifiable source (e.g., a pipe).

• Examples of NPS pollutants: Sediment, oil and grease, toxic chemicals, fertilizers, pesticides, bacteria, nutrients, heavy metals, and thermal pollution.

• Sources: Urban runoff, agricultural runoff, construction sites, failing septic systems, and improper waste disposal.

How Individuals Contribute to NPS Pollution

Everyday actions by individuals can significantly contribute to NPS pollution. Understanding these behaviors is key to reducing their impact.

• Improper Waste Disposal:

  • Littering: Trash carried by wind or stormwater into waterways.

  • Improper disposal of household chemicals: Pouring chemicals, oil, paint, or cleaning products down the drain or on the ground contaminates soil and water.

  • Pet waste: Animal waste left on the ground can be washed into storm drains, polluting water bodies.

• Excessive Use of Lawn and Garden Chemicals:

  • Fertilizers and pesticides: Over-application leads to runoff that pollutes water sources with nutrients and chemicals.

  • Improper application: Applying before rain or in excess increases runoff and contamination.

• Poor Vehicle Maintenance: Leaking oil, antifreeze, and other fluids can be washed into storm drains.

• Erosion and Sedimentation:

  • Construction activities: Improper management leads to soil erosion and runoff.

  • Bare soil: Exposed soil in residential areas can be eroded by rain, carrying sediment into water bodies.

• Inadequate Septic Systems: Failing systems can release untreated sewage into the ground, contaminating groundwater.

How Individuals Can Reduce NPS Pollution

There are several actions individuals can take to minimize their contribution to NPS pollution:

• Properly dispose of waste: Recycle, compost, and dispose of trash and chemicals responsibly.

• Use lawn and garden chemicals responsibly: Apply sparingly and only when necessary, following label instructions.

• Maintain vehicles properly: Fix leaks promptly and dispose of used fluids correctly.

• Control erosion: Plant vegetation, use mulch, and manage construction activities to minimize soil erosion.

• Ensure septic systems are functioning correctly: Have them inspected and pumped regularly.

• Participate in community cleanups: Help remove litter and debris from local waterways.

• Promote awareness: Educate others about NPS pollution and encourage responsible practices.

Nonpoint Source Pollution in Urban Areas

Introduction

Urbanization increases the variety and amount of pollutants carried into water bodies. Urban and suburban areas, with their impervious surfaces (pavement, rooftops), prevent water from soaking into the ground, increasing runoff volume and velocity. This runoff carries pollutants into streams and rivers, impacting ecosystems and water quality.

• Common urban NPS pollutants:

  • Sediment

  • Oil, grease, and toxic chemicals from vehicles

  • Pesticides and nutrients from lawns and gardens

  • Viruses, bacteria, and nutrients from pet waste and failing septic systems

  • Road salts

  • Heavy metals from shingles, vehicles, and other sources

  • Thermal pollution from impervious surfaces

• Impacts: Loss of habitat, polluted drinking water, reduced recreational value, and harm to wildlife.

Low Impact Development (LID)

Definition and Principles

Low Impact Development (LID) is an approach to land development that works with nature to manage stormwater as close to its source as possible. LID uses design techniques that infiltrate, filter, store, evaporate, and detain runoff, aiming to mimic natural hydrology and minimize environmental impact.

• Definition: LID refers to systems and practices that use or mimic natural processes to manage stormwater and reduce runoff and pollution.

• Key principles:

  • Preserve and recreate natural landscape features

  • Minimize effective imperviousness

  • Manage rainfall at the source using decentralized micro-scale controls

Examples of LID Practices

• Rain gardens: Shallow, vegetated basins that collect and absorb runoff from rooftops, sidewalks, and streets.

• Green roofs: Roofs covered with vegetation to absorb rainfall and reduce runoff.

• Permeable pavements: Surfaces that allow water to infiltrate through them, reducing runoff.

• Bioswales: Landscaped channels designed to concentrate and convey stormwater runoff while removing debris and pollution.

• Rain barrels and cisterns: Containers that collect and store rainwater for later use.

Benefits of LID

• Reduces stormwater runoff: By increasing infiltration and evapotranspiration, LID reduces the volume and speed of runoff.

• Improves water quality: Filters pollutants before they reach water bodies.

• Enhances groundwater recharge: Allows more water to soak into the ground.

• Protects aquatic habitats: Reduces erosion and sedimentation in streams and rivers.

• Cost-effective: Can reduce the need for expensive stormwater infrastructure.

Comparison: LID vs. Conventional Stormwater Management

Scientific Principles: Water Cycle and Runoff

• Evapotranspiration: The sum of evaporation and plant transpiration from the Earth's land and ocean surface to the atmosphere.

• Infiltration: The process by which water on the ground surface enters the soil.

• Runoff: Water that flows over the land surface toward water bodies.

Equation for Water Balance:

• = Precipitation

• = Evapotranspiration

• = Runoff

• = Change in storage

Community and Policy Approaches

Role of Individuals, Families, and Local Communities

Individuals and communities play a crucial role in reducing NPS pollution through behavior change, local initiatives, and participation in monitoring and clean-up activities.

• Volunteerism: Participating in cleanups, monitoring water quality, and educating others.

• Citizen science: Collecting data on water quality and reporting pollution incidents.

• Public-private partnerships: Collaborating with local governments and organizations to implement NPS solutions.

Policy and Code Changes

• Revising local codes: Updating ordinances to encourage or require LID practices in new developments.

• Green infrastructure checklists: Tools to help communities identify opportunities for LID and sustainable practices.

• Post-construction controls: Ensuring that stormwater management continues after development is complete.

Summary Table: Key Resources and Topics

Key Takeaways

• Nonpoint source pollution is a major threat to water quality, especially in urban areas.

• Individuals and communities can reduce NPS pollution through responsible behaviors and participation in local initiatives.

• Low Impact Development (LID) offers effective, nature-based solutions for managing stormwater and reducing pollution.

• Policy changes and community engagement are essential for widespread adoption of LID and sustainable water management practices.