Human-Caused Water Pollution: Sources And Entry Points

Human activity can have a significant impact on the water cycle. For example, hydroelectricity was initially considered an excellent solution for renewable energy as it is non-polluting, but damming rivers impacts how the water flow functions, including impeding fish from flowing naturally through the waters, affecting the aquatic ecosystem. This has a knock-on effect on the lakes that typically connect to these rivers, which can put the upstream and downstream water flow out of balance. Deforestation can also harm the water cycle, as fewer trees mean the land and air become drier, affecting surrounding life that previously relied on a certain humidity level. It may also create more run-off and leaching, increasing droughts and floods in certain areas.

Deforestation

As the human population has grown, so has our need for agriculture and, consequently, water to cultivate this agriculture. Irrigation, the artificial watering of the land, is one way that we meet this need. However, this practice displaces water from its natural source, causing leaching or runoff where it used to be.

Trees play a crucial role in the water cycle by absorbing water from the ground and releasing it into the atmosphere through a process called transpiration. They also help to regulate the water cycle by providing shade, which reduces evaporation rates, and by their roots, which help to store water and prevent soil erosion.

When trees are removed through deforestation, the water cycle is disrupted. There is less water vapour in the atmosphere, which can lead to reduced cloud formation and precipitation. This can further exacerbate the effects of droughts and floods caused by increased runoff and leaching.

Additionally, deforestation can lead to increased soil erosion, as tree roots are no longer present to hold the soil in place. This erosion can carry pollutants and sediment into nearby water sources, further contaminating the water cycle.

Irrigation

Another way that irrigation can impact the water cycle is through the use of pesticides and fertilizers. These chemicals can be washed into waterways, contaminating the water and causing harm to the environment and public health. For example, lead in water can cause damage to the brain, kidneys and red blood cells.

It is important to note that irrigation is not the only human activity that can impact the water cycle. Other activities such as deforestation, hydroelectricity, and the use of volatile organic chemicals (VOCs) can also have significant effects on the water cycle.

Hydroelectricity

The disruption of water flow can also affect the balance of upstream and downstream water levels, potentially leading to flooding or reduced water supply in certain areas. Additionally, the construction of dams can alter the natural course of rivers, impacting the surrounding landscape and the habitats that depend on them.

While hydroelectricity has its benefits as a renewable energy source, it is important to recognise its impact on the water cycle and the potential consequences for the environment. To mitigate these effects, careful planning and consideration of ecological factors are necessary when constructing hydroelectric power plants. This includes ensuring fish can pass through the dam and maintaining a healthy water flow both upstream and downstream.

Fertilizers

Nutrients from manure and fertilizers enter lakes and streams through runoff and soil erosion. When soil-test nitrogen (N) and phosphorus (P) increase, greater amounts of plant-available N and P move with water. Runoff water from fields with high soil-test N and P may contain high levels of these dissolved nutrients, increasing the risk of contaminating streams, wetlands and lakes.

Many cities have put a ban on the use of chemical fertilizers in close proximity to lakes and rivers. However, a large proportion of fertilizers end up in the soil organic N pool from where N is mineralized and is taken up by plants and/or lost via leaching during several decades.

Volatile organic chemicals (VOCs)

The water cycle is impacted by human activity in a variety of ways. Water can become contaminated with pollutants and litter, which can enter the atmosphere through evaporation. Human activity such as deforestation can also impact the water cycle by reducing the number of trees, leading to drier land and air, and affecting life that depends on a certain humidity level. Additionally, the use of hydroelectricity, while initially considered a non-polluting source of renewable energy, can alter the natural flow of water by damming rivers and impeding the movement of fish, thus disrupting the aquatic ecosystem.

One way VOCs enter the water cycle is through the evaporation of contaminated water sources. When water evaporates, it carries the VOCs present in it into the atmosphere. These chemicals can then condense and return to the earth's surface through precipitation, contaminating water bodies and contributing to air pollution.

Another way VOCs enter the water cycle is through direct discharge into water bodies. Industrial and agricultural activities often release untreated or partially treated wastewater containing VOCs into rivers, lakes, and oceans. This contamination can have detrimental effects on aquatic life and ecosystems, as well as pose risks to human health when the water is used for drinking or recreational purposes.

To mitigate the impact of VOCs on the water cycle, it is essential to reduce their use and properly dispose of them. Individuals can play a role by choosing sewer-safe cleaners, avoiding harsh chemicals for drain cleaning, and opting for natural alternatives to synthetic fertilizers. Additionally, proper waste management practices, such as disposing of motor oil and other hazardous materials responsibly, can help prevent VOCs from entering the water cycle.

By understanding the sources and impacts of VOCs in the water cycle, we can take proactive measures to reduce their presence and protect this vital resource for future generations.

Frequently asked questions