Ghana’s urban population has more than tripled in the last three decades, from 4 million to almost 14 million people. Competition for land in cities has increased among various land uses. These trends have led to the invasion of ecologically sensitive areas such as wetlands.
Kumasi, the second largest city in Ghana, has a high level of encroachment and this has led to pollution of water bodies. Kumasi’s population growth has been rapid due to its central and strategic location and its functions as an important commercial, traditional and administrative center. In 2022, the population of Kumasi was 3,630,326, with a growth rate of 4.02%. The city’s growth puts pressure on its natural assets.
As scholars of urban planning and chemistry, we conducted a study in the large metropolis of Kumasi to understand the extent of encroachment and pollution of two rivers, Subin and Wiwi. We wanted to understand how cities can be developed and functional without destroying natural resources. We also wanted to know more about the extent of water pollution, the dynamics of land use and water resource regulations, and how they influence the quality of water resources.
We discovered that people were building houses in informal settlements along the rivers. Liquid and solid waste were dumped into rivers. People used land on river banks for agricultural and industrial activities, which had a negative effect on water quality.
We recommend that municipal authorities better monitor what is happening and do more to prevent the degradation of Kumasi’s water bodies.
Effects of land use on the quality of water bodies
We found that in the large metropolis of Kumasi, more land along rivers was being used for industrial, residential and commercial purposes than for green space. Municipal authorities have been ineffective in controlling development in these areas, despite Ghana’s zoning guidelines stating that there should be a 30-meter (100-foot) buffer zone along bodies of water.
Land values in Kumasi are increasing due to rapid urban growth, but values are lower in the wetlands. This difference contributed to city residents building in humid areas. Furthermore, the intense pressure of urbanization on available land has resulted in a high level of invasion of wetlands. The study revealed that 35.4% of land uses within the Wiwi River buffer zone were residential developments.
This research further confirmed that the Wiwi and Subin rivers have been heavily polluted with fecal coliforms over the years. Coliform counts are an indicator of possible fecal contamination and reflect hygiene standards.
The average coliform count exceeded the limits of 400 total coliforms/100ml and 10 fecal coliforms/100ml allowed by the World Health Organization standard. Both rivers are extremely polluted with fecal matter.
The research also confirmed that heavy metals in water bodies were above the WHO recommended standard of 0.01 mg/liter. For example, the average lead (Pb) concentration recorded in the Wiwi and Subin rivers was 0.018–0.031 mg/l and 0.035–0.055, respectively. Exposure to lead is dangerous to your health.
As a result of limited investment in sewage treatment plants, most of the city’s untreated wastewater is discharged into surface water bodies. This has implications for the quality and sustainability of these water bodies.
The study also showed that some city residents dump their waste near the city’s wetlands. During heavy rains, waste runs into the water, affecting water quality and flow.
The inability of municipal authorities to enforce regulations and legislation on land use has allowed people to carry out agricultural activities near rivers. The use of agrochemicals threatens aquatic habitats. Chemicals such as pesticides, herbicides and fertilizers are likely to leak or wash into rivers. The use of polluted river water for irrigation also poses a threat to human health.
Industrial activities along the water bodies include washing bays, automechanical activities, welding, and wood processing. These pose a threat of chemical pollution due to the likely infiltration of petroleum products into the water.
Time for Kumasi to wake up
The development of sustainable cities depends on the ability of municipal authorities to plan for social, environmental and economic growth. Urban growth can coexist with natural resources if human activities located near bodies of water do not threaten their quality and continued existence.
Our study shows that Kumasi developed with little regard for its natural resources. This is a threat to the city’s sustainability. Municipal authorities should implement measures to clean water bodies and convert buffer areas into parks and green spaces. Environmentally friendly urban agriculture can also be promoted along water bodies.
Activities such as disposal of liquid and solid waste must be stopped. The principle “the polluter must pay” must be applied to people who violate environmental regulations.
Urban centers in Ghana need a water resources management policy. Regulatory institutions, such as the Department of Physical Planning and the Environmental Protection Agency, must be restructured and equipped to respond to complex environmental problems emerging in cities. There must be continuous environmental monitoring and regulations must be strictly enforced. The UK River Thames policing model can be adopted to ensure continuous monitoring of water bodies. To monitor and enforce zoning regulations, city authorities and policymakers must invest in technologies like drones.
The Zoning Guidelines and Planning Standards provide standard average setback distances for a buffer zone of 50 to 100 feet from bodies of water. We recommend that the buffer zone be 30 meters (100 feet) away from the wetland. Wetlands are an important ecosystem service that needs to be protected. Ecologically sensitive areas that are 30 meters away from wetlands should be acquired as natural assets of public interest.