Water Quality: Impact Of Human Activity And Environment

Water quality is influenced by a multitude of factors, encompassing both natural processes and human activities. The quality of water is vital for sustaining diverse ecosystems, human health, and various industries. Natural factors that affect water quality include the geology and topography of the surrounding area, the source of the water, and the flow rate. Human activities, such as industrial, agricultural, and urban runoff, can introduce pollutants like detergents, oils, grease, pesticides, and excess nutrients into water bodies, degrading water quality. Additionally, climate events like bushfires can indirectly impact water quality by altering soil structure and vegetation cover, increasing the risk of sediment and pollutant runoff. Water quality standards and management strategies are crucial for maintaining and improving water quality, safeguarding human and ecological well-being.

Industrial, farming, mining, and forestry activities

Industrial Activities

Industries such as distilleries, tanneries, pulp and paper, textiles, food, iron and steel, and nuclear industries are major contributors to water pollution. Various toxic chemicals, organic and inorganic substances, toxic solvents, and volatile organic compounds may be released during industrial production. Arsenic, cadmium, and chromium are vital pollutants discharged into wastewater, and the industrial sector is a significant contributor to harmful pollutants. With increasing urbanization, the volume of wastewater from industrial production has also increased, further degrading water quality. Foreign direct investment in less developed countries has a positive correlation with industrial water pollution.

Farming Activities

Agricultural activities contaminate water with nitrates, phosphorus, pesticides, soil sediments, salts, and pathogens. The use of pesticides, nitrogen fertilizers, and organic farm waste in agriculture are significant causes of water pollution. In water-scarce regions, untreated or partially treated wastewater is often used for irrigation, posing risks to the environment and human health. Pesticides, for example, can adversely affect health through drinking water, and their increased use has been linked to a higher medical disability index. Additionally, untreated wastewater used for irrigation can lead to serious agricultural land and food pollution, pesticide residues, and heavy metal pollution, threatening food safety and human health.

Mining Activities

Mining affects water quality through its heavy use of water in processing ore and through water pollution from discharged mine effluent and seepage from tailings and waste rock impoundments. One of the primary concerns is acid mine drainage, which occurs when large quantities of rock containing sulphide minerals are exposed to air and water, creating sulphuric acid. This process can last for hundreds or even thousands of years and severely degrades water quality, killing aquatic life and rendering water unusable. Another issue is heavy metal contamination, where metals such as arsenic, cobalt, copper, cadmium, lead, silver, and zinc come into contact with water, leaching into and polluting waterways. Additionally, the chemicals used in the mining process, such as cyanide and sulphuric acid, can spill, leak, or leach into nearby water bodies, posing toxic threats to humans and wildlife.

Forestry Activities

Forestry activities, including cultivation, site preparation, fertilisation, and harvesting, can also impact water quality. Some of the key concerns include sediment delivery, nutrient losses, carbon transport, metal and base cation releases, and changes to acidity and temperature. Forest management practices can lead to detrimental effects on water quality and the aquatic environment, including diffuse pollution, carbon transport, and harmful effects on freshwater ecology. However, the development and implementation of best management practices (BMPs), such as the use of buffers, low-impact techniques, and phased felling, have helped reduce and prevent the negative impacts of forestry activities on water quality.

Geology, land cover, soil types, and human activities

The geology of a stream, the surrounding land cover, soil types, and human activities all have a significant impact on water quality. The substrate composition of a stream, such as rocks or metals, can influence the water quality as it flows over and through the stream bed, dissolving and absorbing substances. The surrounding land cover and soil types also play a crucial role. Soil with high amounts of soluble substances, such as limestone, will result in runoff water with high concentrations of calcium carbonate. Additionally, acid sulfate soils, when exposed to air, can release acid and contaminants like heavy metals into nearby waterways, reducing pH and oxygen levels.

Land use and human activities have a profound effect on water quality. Industrial activities, farming, mining, and forestry can introduce various pollutants into rivers, lakes, and groundwater. For instance, industrial processes can increase the concentration of metals and toxic chemicals, add suspended sediments, and affect water temperature and oxygen levels. Similarly, farming practices can increase the presence of nutrients, pesticides, and suspended sediments in water bodies. Urban areas also contribute to water pollution through stormwater runoff, which can carry debris, nutrients, sediments, animal waste, petroleum products, and road salts into rivers and lakes.

Human activities, such as poor land management and vegetation clearance, can further increase salinity levels in soils and waterways. Blackwater events, caused by the accumulation of leaf litter and debris during flooding, can deplete dissolved oxygen levels in water as bacteria consume the high amounts of organic material. Additionally, bushfires can alter soil structure and vegetation cover, increasing the risk of sediment and pollutant runoff into nearby waterways, negatively impacting drinking water, agricultural activities, and aquatic ecosystems.

The impact of human activities on water quality is evident in the introduction of detergents, oil and grease, and pesticides into water sources. These substances, along with litter and garbage, contribute to the problem of runoff, transforming a natural environmental process into a more severe human-induced issue. Overall, a combination of natural factors and human activities influences water quality, highlighting the importance of effective water management strategies to maintain and improve water quality.

Blackwater events and bushfires

Bushfires contribute to blackwater events and affect water quality through several mechanisms. The loss of vegetation cover and altered soil structure make fire-affected areas more susceptible to erosion. Heavy rain after a bushfire can lead to runoff, carrying sediments, ash, burnt material, and pollutants into waterways, reservoirs, and drinking water sources. This can have detrimental effects on agriculture and human safety.

The impact of bushfires on water quality depends on factors such as the geographical features, size of the catchment, intensity and extent of the fire, and the time between the fire and subsequent rainfall. High-intensity fires can cause significant damage to water catchments by destroying ground cover, altering soil structure and hydrology, and increasing stream temperatures due to reduced shade.

Chemical reactions triggered by fires can release nutrients, metals, and other toxicants stored in vegetation and soil. Subsequent rainfall then washes these contaminants into waterways, leading to potential risks for agriculture, human consumption, and ecological balance. The local food chain can be disrupted, with increased water temperatures, higher light availability, and reduced protection for aquatic organisms.

Managing the effects of bushfires on water quality requires effective communication strategies and immediate actions such as establishing water quality monitoring programs, rehabilitating control lines, and implementing sediment and erosion control measures to prevent debris from entering water bodies. While natural regeneration of freshwater catchments can occur within five to twenty years, proactive measures are crucial to mitigate the impact of bushfires on water quality and the surrounding environment.

Urban runoff

One of the primary concerns with urban runoff is the pollutants it carries. As the water flows over roadways and parking lots, it picks up gasoline, motor oil, heavy metals, trash, and other contaminants. Roads and parking lots are significant sources of polycyclic aromatic hydrocarbons (PAHs), which are byproducts of gasoline and other fossil fuel combustion. They also contribute to the presence of heavy metals such as nickel, copper, zinc, cadmium, and lead in the runoff. Roof runoff is another source of pollution, adding high levels of synthetic organic compounds and zinc from galvanized gutters.

The use of fertilizers and pesticides on residential lawns, parks, and golf courses is another factor that affects water quality. When fertilizers are over-applied or improperly used, they can be a significant source of nitrates and phosphorus in urban runoff. Eroding soils and poorly maintained construction sites can also increase sedimentation in runoff, which can directly impact water quality. High levels of sediment can reduce oxygen levels, promote algae growth, and limit the growth of native vegetation, disrupting aquatic ecosystems.

The increased flow and velocity of stormwater caused by urban runoff can have detrimental effects on watercourses that historically experienced little or no water during dry periods, often called ephemeral streams. The high-velocity water rushing down these streams can damage natural features, increase erosion, and harm vegetation, wildlife, and the stream bed. Eutrophication, caused by the presence of fertilizer and organic waste in the runoff, often leads to deadly consequences for fish and other aquatic organisms.

To address the issues associated with urban runoff, effective control measures include reducing the velocity and flow of stormwater and minimizing pollutant discharges. Local governments employ various stormwater management techniques, known as best management practices for water pollution (BMPs), to mitigate the impacts of urban runoff. These techniques may focus on controlling water quantity, improving water quality, or both. Prevention practices include low-impact development (LID) or green infrastructure techniques, such as green roofs and improved chemical handling. Runoff mitigation systems, such as infiltration basins, bioretention systems, and constructed wetlands, are also utilized to manage and treat stormwater before it enters natural water bodies.

Temperature, pH, and dissolved oxygen levels

Temperature

Temperature is a common physical assessment of water quality. It impacts the chemical and biological characteristics of surface water. Warmer water is less capable of holding dissolved oxygen, which is essential for a healthy aquatic ecosystem. Temperature also affects the metabolic rates of aquatic organisms, their sensitivity to pollution, parasites, and disease, and the photosynthesis of aquatic plants. Thermal pollution, often caused by industrial or urban activity, can have a detrimental effect on water quality.

PH

The pH of water is a measure of how acidic or basic it is, on a scale of 0-14, with 7 being neutral. The pH of water is important as it determines the solubility and biological availability of chemical constituents such as nutrients and heavy metals. A changing pH in a stream can indicate increasing pollution or some other environmental factor. A pH of less than 7 indicates acidity, which can be harmful to aquatic life and corrode metals. A pH of greater than 7 is alkaline and can cause a bitter taste and a build-up of deposits in water pipes and appliances.

Dissolved Oxygen

Dissolved oxygen (DO) is the amount of oxygen present in water, which aquatic animals need to breathe. Low levels of oxygen (hypoxia) or no oxygen levels (anoxia) can be caused by the decomposition of excess organic materials by microorganisms. DO is considered a direct indicator of water quality as it reflects the aquatic resource's ability to support life. DO levels below 5mg/L are considered stressful for fish, and levels below 3mg/L are too low to support fish.

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