Urban Sprawl And Industrial Rush: Rivers In Peril

Urbanisation and industrialisation are necessary for economic growth, but they have also led to a significant increase in river pollution. Rivers across the world have been straightened, dammed, deepened, reinforced, diverted, embanked, and culverted for human convenience, which has impacted their characteristics, including water flow, sediment movement, fish migration, and erosion. This has resulted in agricultural pollution, with soil being lost at 10 times the rate it is created, and the loss of wetlands, which act as biodiversity hotspots and store huge amounts of water. Urban areas generate over two-thirds of the world's gross domestic product and, by 2050, are projected to accommodate more than two-thirds of the global population. This rapid urbanisation increases the use of freshwater resources and contributes to water stress and scarcity.

Urban waste

Poor waste management practices can exacerbate the problem of urban waste pollution in rivers. In areas with inadequate waste collection systems, trash may be directly dumped into rivers or washed into them during surface runoff. This was the case with the Citarum River in Indonesia, which is considered one of the world's most heavily polluted rivers due to high amounts of plastic waste and other types of trash.

Sewer systems can also be a source of river pollution in urban areas. As more people connect to sewer systems, the amount of wastewater increases, and if this wastewater is not properly treated, it can contaminate rivers. Studies have shown that even with moderate and high urbanization rates, the future inputs of most pollutants into rivers are projected to be higher. This is due to the increased number of people connected to sewer systems and the higher rate of urbanization.

The impact of urban waste on river pollution can be seen in the example of the Chicago River, which was once a toxic wasteland due to industrial and human waste. The river served as a dumping ground for the city's growing population, and the resulting pollution contaminated the city's drinking water, leading to frequent cholera epidemics. Through restoration efforts and changing public perception, the Chicago River has now been transformed into an urban oasis, with Chicagoans embracing their once-polluted river.

To address the issue of urban waste pollution in rivers, it is essential to improve waste management practices and invest in advanced wastewater treatment infrastructure. This includes developing better waste collection systems and ensuring that wastewater treatment rates are high enough to effectively remove pollutants before the water is released back into the environment. By taking these steps, we can work towards reducing the impact of urban waste on our rivers and ensuring clean water availability for future generations.

Sewage and sanitation

Urbanisation and industrialisation have a significant impact on river pollution, particularly when it comes to sewage and sanitation. As cities expand, the demand for water and sanitation services increases, and inadequate infrastructure can lead to river pollution.

Inadequate sanitation and sewage systems can contaminate rivers in several ways. Firstly, untreated or partially treated sewage can be discharged directly into rivers, leading to the spread of harmful bacteria, viruses, and parasites. This can pose a severe health risk to communities, with diseases such as cholera thriving in such environments.

Secondly, rapid urbanisation often results in increased pavement and impervious surfaces. During storms, the runoff from these surfaces enters storm sewers and eventually flows into rivers. This can cause flooding and erosion along river banks. The increased volume of water can overwhelm natural streams, leading to further pollution.

Additionally, the use of large wells can lower the underground water table, causing other wells to run dry and affecting the stability of the land above. This can result in sinkholes and land subsidence, further altering natural water flows and contributing to river pollution.

The impact of urbanisation on river pollution is particularly evident when comparing urban and rural areas. For example, in South Asia, only 23% of the urban population has access to safely managed sanitation, while 62% of the global urban population has access, compared to 44% in rural areas. This disparity highlights the challenges of providing adequate sanitation services in rapidly growing urban centres.

To address these issues, interventions such as safe wastewater treatment, improved sanitation infrastructure, and sustainable practices are crucial. By implementing advanced technologies and following guidelines such as the New Urban Agenda, governments can work towards providing sustainable water and sanitation services for all urban residents, reducing river pollution, and improving public and environmental health.

Loss of wetlands

Wetlands are among the most biologically productive ecosystems in the world. They support a wide range of human activities, from commercial fishing and shellfishing to recreation and education. Wetlands are essential for improving water quality as their highly developed root systems hold the soil in place and filter pollutants from surface waters.

However, human activities such as agriculture and development have led to the draining and filling of wetlands, resulting in habitat loss and a decline in wetland functions. This loss of wetlands can have significant ecological impacts. For instance, it can decrease habitat and landscape diversity, as well as connectivity among aquatic resources. With fewer wetlands available to act as natural filters, pollutants from surface waters can become more concentrated in the remaining wetlands, further compromising their ecological functions.

The conversion from one wetland type to another can also have detrimental effects. For example, cutting down trees in forested wetlands can alter habitat types and community structure. Additionally, human modifications such as pipes and channels can change wetland types, elevation, or hydrology. The withdrawal of groundwater or surface waters can reduce the flow of water into wetlands, further compromising their health.

In the context of rapid urbanisation and industrialisation, the loss of wetlands exacerbates river pollution. As urban areas expand, there is increased competition for water between cities and agriculture. Inadequate wastewater treatment leads to the contamination of water with multiple pollutants, including nutrients, pathogens, plastics, and chemicals. With a reduced number of wetlands to act as buffers and filters, these pollutants can make their way into rivers, posing a severe threat to the availability of clean water.

Invasive species

Urbanisation and industrialisation are necessary for economic growth, but the way cities and industries are currently developed is unsustainable. Urban areas already accommodate more than half of the global population and generate over two-thirds of the world's gross domestic product. By 2050, more than two-thirds of the world's population will live in cities. This rapid urbanisation increases competition for water between cities and agriculture, and more urban waste results in the contamination of water with multiple pollutants.

Urbanisation also creates disturbed environments where invasive species thrive and outcompete native species. Many invasive plant species, for example, grow along roads and highways. The use of asphalt and other dark-coloured materials in urban areas increases the amount of sunlight absorbed, creating urban heat islands with higher temperatures than surrounding areas. Paving land with concrete increases water runoff, which, in turn, increases erosion and decreases soil quality, leading to a decline in water quality as more sediment and pollutants end up in rivers and streams.

The Fez metropolitan area in Morocco is a case in point. The Fez River surrounds the Fez agglomeration, receiving the wastewaters of this developing city and then flowing into the Sebou, the main Moroccan river. The Fez's river sediments were found to be heavily polluted, exhibiting bottom-up accumulation trends, a clear sign of recent pollution from the untreated wastewaters of Fez city.

River engineering

The human influence on rivers can be divided into six chronological stages. River engineering can be used to improve the behaviour of a river or hold it back to adapt to our infrastructure. While this can be viewed as a positive impact, pollution has an undoubtedly negative impact on the environment.

Large dams and hydropower are an important part of today's energy supply and are a significant aspect of river engineering. While small quantities of water are released through turbines to meet the growing power demand, this also flattens the rivers' hydrographs and is responsible for a decline in seasonal hydraulic variability. This leads to a loss of delta-building dynamics as sediments are stored in the reservoir. As a result, small-scale users of the deltas lose the biodiversity and ecosystem productivity they depend on.

Alternate land use, deforestation, afforestation, and different types of river engineering have also led to changes in hydrologic processes, such as runoff. For example, illegal mining activity can change the soil structure and increase or decrease runoff. In southern Ghana's Lower Pra River Basin, the percentage of runoff change linked to human activity is up to 66%.

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