Human activities on most rivers significantly impact the river ecosystem. This is because the relationship between the living organism and their environments is complex in nature. Therefore, when the environment is altered by human activities it negatively impact on the living organisms within that region. Some of these human activities include irrigation, reservoir creation, hydropower generation, industrial, agricultural and municipal waste discharge, over harvesting among others. On the other hand, the impacts include pollution, river flow withdrawal, water clogging, river flow redistribution in time, thermal pollution, river flow withdrawal among others. River ecosystems are largely affected by human activities. The relationship between the two living organisms’ environments is tremendously complex. Agricultural intensifications have led to chemical and nutrient loss to rivers resulting to eutrophication of backwater regions.
In this paper, we will consider pollution as a human activity in Buriganga River in Bangladesh (Ahmad et al., 2010). Bangladesh is among the most populated areas in the world. In addition to its population, the region is home to several companies including textile mills, plastic based factories, and fertilizer based factories. The major sources of pollution to the river include medical waste from nearby hospitals, domestic garbage’s, plastic and petroleum wastes, sewage discharge, rotting fruits and vegetables and dead animals. According to statistics, it was found that 4,500 tons of solid waste are released into the river each day from Dhaka city (Ahmad et al., 2010). In addition to the solid waste discharged into the rivers, about 80% of the sewage release into the river is untreated. Pollution is a product of people building infrastructures in near streams. Forest clearing to create a farmland has resulted in on-going erosion, and large amounts of sediment have been deposited in water bodies. Humans have tried to improve their agriculture production through intensification (fertilizer application) which has increased nutrients concentrations mainly phosphorus and nitrogen the key fertilizer components leading to slow-moving rivers eutrophication. Urban activities contribute to river pollutions. Besides, industrial and household effluents and sewage deposit contaminants such as heavy metals and PAHs in streams. Emission such as nitrous oxide and sulfur dioxide from the power station and factories find their way into rivers ecosystems through acid rains.
Human activities lead to excessive water withdrawal which has brought several consequences to river systems. Industries take about 20 percent, residential area 9.9 percent and agriculture 70.1 percent. Most rivers are in the drying process because of large withdrawal. Irrigation and household usages have led to sharp drop in levels of rivers. In addition, flow modification has significantly contributed to water levels in rivers. The building of dams alters the temperatures, sediments, and flow in river systems. In modern society, there are over 50,000 dams with heights greater than 15 meters (Boon & Raven, 2012). The dams are estimated to take away about 6.5 trillion meters cubed of water which is approximately 15 percent of world river flow. These facts prove that human activities lower river levels. Decreased flow affects the number of aquatic habitats because it removes and reduces populations of aquatic life. Besides, modification influences tributary river flow. Subsequently, it has an impact on Riverside vegetation, they decline in number, as a result,rivers become more vulnerable to pollution. Rivers systems are connected, and culverts, floodgates and dams barriers disconnect them, therefore, preventing the migration of species. Boon and Raven (2012) argue that factory emission and carbon dioxide gas release from cars and plasticburning result in global warming. These activities affect river ecosystems by leading to increased evaporation, early spring melting, and high rain levels. Owing to evaporation and other human alterations river ecosystems are mostly affected. Biogenic substance reduction in stream flow as well as seasonal chemical leveling, result from hydro-chemical river regime change.
Pollution results to harmful effects to water life, humans and animals. Depending on the types of pollutants and the concentration discharged into rivers, the effects can be catastrophic. The main effect of pollution in this river is the loss of aquatic life. It has been found that no aquatic life can service in Buriganga Rivers as a result of the pollution (Ahmad et al., 2010). In addition to the death of aquatic life, these pollutants have resulted in the disruption of the natural food chains. When some of the livestock take the polluted water, heavy metals such as lead and cadmium from fertilizer based wastes find themselves into the food chain.
Besides, the river pollution has contributed to the breeding of algae and this is the major cause of death for aquatic animals. This is because these algae consume all the oxygen dissolved in water, therefore, affecting fish and small beneficial aquatic organisms (Ahmad et al., 2010). Also, these algae clog fish gills reducing their chances of survival. Some of the plants around the river have been affected by the polluted water. This is because some wastes products containing high concentration of acidic components burn up plants. Therefore, nearby plants have been affected by these pollutants consequently affecting smaller organisms that depend on these plants (Ahmad, et al., 2010).
Water PH is lowered by pollution affecting river organisms from vertebrates to algae. As the PH decreases, it leads to the decline of biodiversity. Physical riverbeds disturbances caused by human have had a significant impact on rivers ecosystem. Extraction of fossils and building materials from riverbeds, activities such a dredging works, constructions of pipelines and underwater sewage pipes cause disturbances (Boon & Raven, 2012). These activities alter the riverbed evolution processes that impact river’s natural habitat. Large massifs extraction of riverbeds ground result to straightening and deepening of rivers as well as lowering water levels. Harvesting activities are rampant in modern society. Boon and Raven (2012) argue that river ecosystem excess fish harvesting has reduced the number of water species. Human activities have resulted to water clogging. It is suggested that communal waste and deposits of solid industrial material have led to river clogging. Besides, river transportation causes oil spillage affecting air circulation in water due to oil layer formed. Therefore, water species are likely to lose lives.
The best strategy to counter the impact of pollution in Buriganga River is for the government to formulate strict policies aimed at reducing discharge into the river. This will see companies treating waste products before releasing it into the river.
Beside, few chemicals should be used in households so as to reduce the domestic discharge into the river. Therefore, people in Dhaka City should be encouraged to use “green products” as provided by the Environment Protection Agency (EPA) (Saha & Hossain, 2011). For example, vinegar and baking soda can be used for household cleaning since they are nontoxic.
The river flow should also be increased so as to clean it. However, implementation of this strategy is difficult since the Himalaya Glacier feeding the river is shrinking day by day as a result of climatic change (Saha & Hossain, 2011).
Proper measures of disposing of non-biodegradable should be encouraged. For instance, ammonia, motor oil, paints, pool chemicals and cleaning solvents should not be disposed into the river.
Since plastic based products are among the key pollutants in this region, the population can be encouraged to avoid using plastic products. Instead, glass, prodegradant concentrates, and keratin beside plastics should be used (Saha & Hossain, 2011).
Agriculture pollution can be reduced through used of organic manure in place of fertilizers. In addition, governments should discourage riverside faming and construction activities.
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