How Overland Water Sources Become Polluted

Water is essential for life, but it can also be a source of pollution. When precipitation falls on land, it can become runoff, which is water that flows over the surface of the ground and travels towards nearby water bodies. This runoff can pick up various pollutants along the way, such as fertilizers, oils, and debris, leading to nonpoint source (NPS) pollution. NPS pollution is a leading cause of water quality issues and can impact ecosystems and the quality of water that enters our lakes, rivers, and oceans.

Runoff from rain or snowmelt

Soil has a certain infiltration capacity, which is affected by the level of antecedent soil moisture. When the soil is already saturated, or when the rate of rainfall exceeds the rate of water infiltration, surface runoff occurs. This is known as saturation excess overland flow or Dunne runoff. Additionally, impervious surfaces such as roads, buildings, parking lots, roofs, and pavements prevent water from soaking into the ground, contributing to runoff.

In natural settings, soil, plants, and trees play a crucial role in absorbing excess water. However, in developed areas, the presence of impervious surfaces and stormwater systems can exacerbate the problem. Stormwater runoff is directed into natural systems like streams, rivers, and lakes, potentially carrying pollutants such as chemicals, fertilizers, pesticides, debris, oil, and grease along with it.

The impact of runoff from rain or snowmelt can vary depending on geographical factors. For example, in high mountain regions, streams may rise on sunny days due to increased snowmelt and fall on cloudy days. In alpine regions, snowmelt is a significant component of runoff, and when combined with excessive rainfall, it can lead to flooding, landslides, and debris flows.

To mitigate the negative impacts of runoff, it is essential to implement effective stormwater management practices. This includes ensuring that stormwater drains and gutters are clear of debris and properly maintained. Additionally, natural solutions such as increasing forest cover and utilizing tree roots for water absorption can also help reduce the adverse effects of runoff from rain or snowmelt.

Point-source pollution

Runoff is the primary water source that becomes polluted as it travels over land. As water travels over the land, it can pick up various pollutants, including chemicals, fertilisers, debris, oils, and grease, which can lead to the contamination of nearby ponds, rivers, and oceans. This process is known as "nonpoint-source pollution" and is challenging to address due to its diverse sources.

In contrast, "point-source pollution" is defined by the United States Environmental Protection Agency (EPA) as any contaminant that enters the environment from a single, identifiable, and confined place. This includes discrete conveyances such as pipes, ditches, channels, tunnels, wells, containers, or vessels. Point-source pollution is easier to identify and regulate compared to nonpoint-source pollution.

• Industrial Discharges: Factories and manufacturing plants often release pollutants through their waste streams. This can include toxic chemicals, heavy metals, and other hazardous substances. For example, the Montrose Chemical Corporation discharged millions of pounds of DDT into the ocean off the coast of Southern California, causing widespread environmental damage.
• Municipal Wastewater Treatment Plants: These plants collect and treat wastewater from urban areas before releasing it back into the environment. If the treatment processes are inadequate or fail, the discharged water can contain harmful bacteria, nutrients, and chemicals, leading to point-source pollution in nearby water bodies.
• Power Plants: The release of pollutants from power generation facilities, such as coal-fired plants, can result in point-source pollution. This includes air emissions that contribute to acid rain and ash disposal, which can leach toxic substances into nearby water sources.
• Mining Operations: Discharges from mines can contain high levels of acids, heavy metals, and other toxic chemicals. These pollutants can contaminate nearby rivers, streams, and groundwater sources, causing severe ecological damage and threatening the health of local communities.
• Oil and Gas Industry: Accidents or improper handling of oil and gas drilling and refining processes can lead to point-source pollution. Oil spills, for instance, can have devastating impacts on marine environments and the wildlife that depends on them.

It is important to note that regulatory agencies like the EPA play a crucial role in identifying, monitoring, and regulating point-source pollution to minimise its impact on the environment and human health.

Nonpoint-source pollution

Nonpoint-source (NPS) pollution is the leading cause of water quality issues. It is defined as any source of water pollution that does not meet the legal definition of "point source" as outlined in the Clean Water Act. Point sources refer to confined and discrete conveyances, such as pipes, ditches, tunnels, and vessels, from which pollutants are discharged.

NPS pollution arises from various diffuse sources, including land runoff, precipitation, atmospheric deposition, drainage, seepage, or hydrologic modification. As rainfall or snowmelt moves over and through the ground, it picks up and carries natural and human-made pollutants, ultimately depositing them into lakes, rivers, wetlands, coastal waters, and groundwater.

In Illinois, for example, NPS pollution stems from runoff from farm fields, livestock facilities, construction sites, lawns, city streets, parking lots, surface coal mines, and forestry operations. The major sources of NPS pollution in this state fall into two categories: agriculture and urban runoff. Urban runoff flows through storm drains and pipes, directly reaching lakes and streams without undergoing treatment.

The effects of NPS pollutants on specific bodies of water may vary and are not always fully understood. However, it is known that these pollutants negatively impact drinking water supplies, recreational activities, fisheries, and wildlife. Sediment, a common NPS pollutant, is soil eroded from farm fields, construction sites, and streambanks. When sediment reaches lakes and streams, it reduces water clarity, impairs aquatic organisms' feeding and breathing, damages fish gills and spawning habitats, and inhibits plant growth by reducing sunlight penetration. Additionally, sediments can carry other harmful substances, such as metals and toxic chemicals.

Groundwater contamination

Groundwater is a critical source of drinking water for millions of people worldwide. As it flows through the ground, it can dissolve metals like iron and manganese, which may later be found in high concentrations. While the ground naturally filters out particulate matter, leaving groundwater clear and clean, it is still vulnerable to contamination by human-induced and natural chemicals, biological organisms, and other potentially harmful agents.

Atmospheric contaminants also play a role in groundwater contamination. As groundwater is part of the hydrologic cycle, it can be affected by pollutants in other parts of the cycle, including the atmosphere and surface water bodies. Industrial discharges, urban activities, agriculture, and groundwater pumpage further contribute to groundwater contamination.

The consequences of groundwater contamination are significant. Contaminated groundwater can lead to serious health issues, including diseases such as hepatitis and dysentery, and even certain types of cancer. It also harms wildlife and disrupts aquatic ecosystems. Therefore, preventing and mitigating groundwater contamination is crucial to ensure a safe and sustainable water supply for human and environmental well-being.

To address groundwater contamination, it is essential to identify potential sources of pollution and implement proper waste disposal practices, such as ensuring secure storage tanks and effective septic systems. Regular monitoring and assessment of groundwater quality are also necessary to detect contamination early on and implement mitigation strategies. By prioritizing the protection of groundwater resources, we can safeguard the health and well-being of both human populations and ecosystems that depend on this vital water source.

Pharmaceuticals in water

Pharmaceuticals are increasingly being found in water bodies, including lakes, rivers, and streams, as well as in groundwater and drinking water. This is a growing concern as it may have harmful effects on aquatic life and could potentially impact human health.

There are several sources through which pharmaceuticals enter water bodies. One significant source is human excretion. It is estimated that up to 90% of oral medications that pass through the human body end up in the water supply. Drugs that are applied topically, such as creams or lotions, can also contribute to water pollution when they are washed off. Additionally, pharmaceuticals can enter the water supply when unused or expired drugs are flushed down the toilet or disposed of down the drain, a practice that is surprisingly common. Surveys from various countries, including Germany, the United Kingdom, and Canada, have found that a significant percentage of respondents dispose of unwanted pharmaceuticals in this manner.

Another source of pharmaceuticals in water is the pharmaceutical manufacturing industry. A U.S. Geological Survey study found that contamination levels downstream from drug manufacturing plants were significantly higher than those at comparable facilities. Effluents from wastewater treatment plants that receive discharge from pharmaceutical manufacturing facilities can have much higher concentrations of pharmaceuticals than those that do not.

Agriculture is also a major contributor to pharmaceutical pollution in water. Hormones and antibiotics are commonly used in large-scale poultry and livestock operations, and these can leach into groundwater or enter waterways. A U.S. Geological Survey study found measurable amounts of medications in 80% of water samples drawn from a network of 139 streams in 30 states.

The presence of pharmaceuticals in water can have detrimental effects on aquatic life, including insects, fish, and birds. While there is currently no evidence of harm to humans from pharmaceutical pollution in water, studies suggest that the combination of various pharmaceuticals, even at minuscule levels, could potentially have negative health effects, especially if they interact with other substances consumed by individuals.

It is important to address the issue of pharmaceuticals in water through proper disposal practices and improved wastewater treatment methods to prevent potential harm to both the environment and human health.

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