Understanding Nonpoint Water Pollution: What's The Source?

Water pollution is broadly classified into two types: point source and non-point source. Point source pollution refers to pollution that comes from a single, identifiable source, such as a sewage treatment plant, oil refinery, or factory. Conversely, non-point source pollution refers to pollution that comes from multiple sources and is more widespread, making it challenging to trace back to a single point of discharge. Non-point source pollution, also known as NPS pollution, is caused by rainfall or snowmelt carrying pollutants from various human and natural sources and depositing them into waterways. This type of pollution is the leading cause of water quality issues in many states, impacting drinking water supplies, recreation, fisheries, and wildlife.

Suburban development

Water pollution is divided into two main categories: point sources and nonpoint sources. Point source pollution refers to contamination that comes from a single, identifiable source that can be easily traced, such as a pipe or a facility. On the other hand, nonpoint source pollution is more widespread and comes from multiple sources, making it challenging to trace back to a single point of discharge.

During rainstorms, for example, water can wash off roads and carry oil, heavy metals, and trash into nearby rivers or streams. This runoff from urban streets represents nonpoint source pollution as it does not come from a single identifiable source. Similarly, agricultural runoff from suburban areas can collect fertilizers and pesticides from farm fields, transporting them into water bodies and contributing to pollution.

The impact of suburban development on water quality is significant. Urbanization increases the variety and amount of pollutants carried into the water. The presence of buildings, pavement, and compacted landscapes in urban and suburban areas prevents rain and snowmelt from soaking into the ground. This leads to an increased volume and velocity of stormwater runoff, which can carry pollutants and harm fish and wildlife populations, native vegetation, drinking water sources, and recreational areas.

To address the issue of nonpoint source pollution from suburban development, various management practices and guidelines have been proposed. The US Environmental Protection Agency (EPA) provides guidance and best management practices (BMPs) to help citizens, municipalities, and environmental professionals control and mitigate the impact of urban and suburban runoff on water quality. Techniques such as low impact development (LID) and green infrastructure aim to preserve and restore green spaces, treat stormwater as a resource, and promote its natural movement within ecosystems.

Urban runoff

From the storm drains, the contaminated water enters a network of pipes known as a municipal separate storm sewer system (MS4). Unlike wastewater from homes, which goes to treatment plants, the water in MS4 systems is not treated and flows directly into local streams, rivers, lakes, or other water bodies. This untreated water carries with it all the pollutants picked up during urban runoff, posing a significant threat to the health of these aquatic ecosystems and the plants, animals, and humans that depend on them.

The impact of urban runoff on waterway health is significant. The pollutants introduced through this process can have detrimental effects on aquatic life, including fish and other organisms. For example, sediment, which is often carried by runoff from construction sites and streambanks, can damage fish gills and impede the breathing of aquatic insects. It can also reduce sunlight penetration, hindering plant growth, and cloud the water, making it difficult for aquatic organisms to feed.

Additionally, nutrients from fertilizers and animal waste can cause excessive algae growth in lakes and streams, leading to algal blooms. When the algae eventually die, they are broken down by bacteria, which consume oxygen in the process, creating oxygen-deprived zones that make it difficult for fish and other aquatic life to survive. The presence of bacteria and other pathogens in the water can also pose serious health risks to humans and pets, impacting our ability to safely use water for recreation, drinking, and other purposes.

Agricultural runoff

Additionally, agricultural runoff can lead to sedimentation, where soil erosion from farm fields and construction sites results in the deposition of sediment into water bodies. This sedimentation can have several negative consequences, including reduced sunlight penetration, which hinders plant growth, and damage to fish gills and the breathing apparatus of aquatic insects. Sediment can also act as a carrier for other pollutants, including metals and toxic chemicals, further degrading water quality.

The impact of agricultural runoff on water quality has been recognized, and efforts have been made to address this issue. The National Water Quality Initiative (NWQI) was launched in 2012 as a partnership between the USDA NRCS, EPA, and state nonpoint source programs. The NWQI aims to improve water quality by accelerating the adoption of voluntary conservation practices, such as contour strip cropping, which reduces erosion and runoff. Additionally, farmers are encouraged to store livestock manure in lagoons, covered stockpiles, or protected upland areas to minimize runoff risks.

Overall, agricultural runoff is a significant contributor to nonpoint source water pollution, and addressing this issue is crucial for maintaining healthy aquatic ecosystems and ensuring safe drinking water supplies. By implementing conservation practices and adopting more sustainable agricultural methods, it is possible to mitigate the negative impacts of agricultural runoff on water quality.

Habitat modification

Nonpoint source (NPS) pollution is the leading cause of water quality problems. NPS pollution is caused by rainfall or snowmelt moving over and through the ground, picking up and carrying away natural and human-made pollutants, and depositing them into lakes, rivers, wetlands, coastal waters, and groundwater. One of the major sources of NPS pollution is habitat modification, which refers to the channelization of streams and the disturbance of riparian corridors—the areas of land immediately adjacent to stream banks.

Human activities such as agriculture, urbanization, deforestation, resource extraction, and pollution release directly contribute to habitat modification and loss. For example, the conversion of forests and prairies into cropland or the redevelopment of conservation lands for high-priced crops can result in habitat destruction. Additionally, practices like dredging, bottom trawling, and dynamiting can cause widespread destruction in aquatic habitats, damaging shelters, reducing food availability, and hindering the breeding capabilities of organisms.

Climate change is another emerging driver of habitat loss and modification. Rising temperatures and sea levels can submerge coastal habitats, impacting species that depend on specific temperature ranges or elevations, such as the American pika. Furthermore, erratic atmospheric, biogeochemical, and hydrological cycles caused by climate change can lead to habitat damage and loss of biodiversity.

To address habitat modification and loss, habitat restoration aims to rehabilitate areas by recreating functioning ecosystems. This process requires a deep understanding of species' life cycles, interactions, and the specific needs of each species in terms of food, water, nutrients, space, and shelter.

Sediment

Moreover, sediment can act as a carrier for other pollutants, including metals and toxic chemicals. These pollutants can be harmful to both the aquatic environment and human health. An example of a toxic chemical is pesticides, which can enter water bodies through agricultural runoff. Sediment and contaminants can be managed through the use of retention ponds, constructed wetlands, and buffer strips, which help capture and slow down runoff, allowing sediments and pollutants to settle out of the water.

In summary, sediment is a significant contributor to NPS water pollution, and its impact on water quality and aquatic life is profound. By implementing various strategies, such as sediment fences and retention ponds, we can work towards reducing the amount of sediment entering our water bodies and improving the overall health of our aquatic ecosystems.

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