For decades, dams and rivers – small and big – have continued to provide immense benefits to humanity. From provision of water for domestic use to powering machines for electricity generation, these hydro resources remain vital to not only the existence of humanity, but also for economic development.
Whilst the benefits of rivers and dams remain clearly defined and known by many, the rising environmental challenges such as deforestation and climate change continue to pose a big threat not only to the water bodies but to companies like Kenya Electricity Generating Company PLC (KenGen) that operate its hydropower plants which rely heavily on rainfall.
Data from the United Nations indicates that 2019 was the second warmest year on record and the end of the warmest decade (2010- 2019) ever recorded. Although a lot of gains on climate change have been achieved during the COVID-19 pandemic period through reduction of carbon emissions especially by the suspension of world travels, more action is needed such as planting trees, particularly in water catchment areas.
Why is tree planting along the banks of rivers and dams vital? Here are some reasons:
1. Stabilisation of Rivers and Dam Banks
Tree planting is effective to stabilize banks as they help in stabilizing the soil around rivers, thereby increasing their lifespan and the benefits to agriculture and hydroelectric power generation.
As such, efforts by individuals and organisations towards tree growing for bank stabilisation ought to be accelerated. As part of corporate efforts to enhance sustainability our hydroelectric power generation in the financial year 2019/2020. KenGen, through its conservation efforts planted more than 2,500 trees, 25,600 sisals in upper Tana Region while in the full year 2020/2021 35,000 sisals and 8,000 indigenous trees were planted to ensure the dams are protected from erosion. In addition, through KenGen’s ambitious social afforestation programme a total 50,634 assorted seedlings were issued to communities for agroforestry and woodlots establishment on farms. This approach is instrumental in ensuring that the upper tana river catchments is conserved, thereby guaranteeing sustainability of energy generation operations. Grass seedlings, gabion installation and Bamboo establishment along riverbanks are some of the many initiatives the company has embraced as part of the bank stabilisation measures along river Mathioya catchment which has so far yielded good results
Currently, KenGen has accelerated environmental conservation across its hydropower stations namely: Turkwel, Sondu-Miriu, Sangoro, Mesco, Wanji, Gogo, Tana, Sagana, Masinga, Kamburu, Kindaruma, Gitaru and Kiambere.
2. Reduction of Soil Erosion
Erosion of rivers banks remain a major contributor to siltation of dams which ultimately reduces the storage capacity of reservoirs, thereby impacting negatively on power generation capacity not to mention their lifespan. Trees are effective in managing soil erosion as they assist to stabilize the soils, reduce the erosivity of the landscape and enhance percolation greatly reducing the silt load that find its way to the reservoirs. As part of the efforts to accelerate uptake of tree planting within the Upper Tana buffer communities, KenGen runs a dedicated tree nursery with an annual output of about 10,0000 seedlings that are given out for free.
In addition, KenGen has been able to achieve immense results through initiatives like the Green Initiative Challenge (GIC), which is an ambitious project implemented through the KenGen Foundation aiming to plant more than 300,000 trees in close to 1,000 schools in Kenya’s arid and semi-arid areas. The 10-year project, now in its fifth phase, further aims to plant more than 100,000 fruit seedlings. In its entirety, the project is expected to cover over 500 acres of land.
3. Carbon Sinks
Climate change remains among the major catastrophes facing humans. Climate change and its impacts have devasting effects on human population. Climate change mitigation is therefore the focus worldwide to slow the pace of devastating climate change impacts. Trees are significant carbon sinks and critical in offsetting our carbon footprint. Global warming has accelerated the situation because of its adverse effect on rivers and dams, thereby exacerbating the need for more trees in the ecosystem. This forms the basis for the call to accelerate reforestation.
The three reasons above are just among many others that can illustrate the importance of tree planting in safeguarding water bodies in addition to mitigating the adverse effects of climate change on the environment. Tree growing have other benefits like providing habitat for wildlife and enhancing the green economy. As such, if individuals and organisations accelerate their efforts in tree growing especially around water bodies and catchments, a lot of the environmental threats shall be kept at bay.
There has been a big misconception that dams cause floods, but the reverse is true, in many regions around the world, dams have purposely been constructed to mitigate floods that are among destructive natural disasters that occur as a result of excess water in flood-prone regions.
In Kenya, a case study to demystify the role of dams in controlling floods can be cited from the Seven Forks Dams that are in the Eastern part of the country.
For decades, the Seven Forks Dams in the lower Tana region of the Eastern part of Kenya have been known for power generation by Kenya Electricity Generating Company (KenGen). However, what many people are not aware of is that as much as the dams are used to produce electricity, they also play a key role in mitigating flooding downstream during extremely rainy seasons.
How does the Seven Forks Dams in the eastern region work to mitigate against flooding?
The concept around dams controlling flooding is simple: the reservoirs hold huge amounts of water that could have naturally flown downstream, therefore filling rivers and breaking banks. For the case of the Seven Forks cascade, five such dams are involved in this concept whereby once each dam reaches its maximum levels, the excess water naturally overflows from one dam to the next through the natural river channel.
Masinga is the main reservoir and the first dam in the cascade with a capacity of 1.56 billion cubic metres. The dam, commissioned in 1981, has a power plant that generates 40MW of electric power and besides that its reservoir occupies a surface area of 120km2. With this amount of storage space, the dam can hold a lot of water, thereby lessening excess flows in the downstream region.
Water from Masinga dam is conveyed to the next dam - Kamburu which was commissioned in 1974. Kamburu generates 94MW and has a capacity of 150 million cubic metres with its main sources of water being Masinga Dam and River Thiba. With the addition of water from the River Thiba, more water is likely to spill downstream, but it is conveyed to the next power station (Gitaru) through a 2.9-kilometre tailrace tunnel.
Gitaru dam, with a water capacity of 20 million cubic metres holds more water from going downstream. Here, this water is harnessed to generate 225MW, making this plant the biggest hydropower station in East Africa in terms of installed capacity. Water from this dam is then passed on to Kindaruma, the oldest power station in the cascade via an underground 4.7-kilometre tailrace tunnel.
Water from Gitaru and other seasonal rivers feeds the Kindaruma dam which was commissioned in 1968. Currently, this dam hosts the first major power station in Kenya with an installed capacity of 72MW and once it overflows, water is conveyed to the last dam in the cascade which is the Kiambere dam.
Kiambere dam was commissioned in 1988 with an installed capacity of 168MW and has a water holding capacity of 585 million cubic metres. As a way of mitigating floods, the dam has a natural spillway, a low-level outlet at the main dam, an emergency spillway and intake at the saddle dam. The emergency spillway is provided to mitigate against extreme floods. After this dam, water flows naturally downstream to River Tana, then to the Indian Ocean.
That said, these dams have over the years continued to hold huge volumes of water that would have otherwise caused major floods in the lower region if allowed to flow freely. After KenGen Hydro-electricity dams, the Government through its development agenda has proposed to build more multipurpose dams in the lower parts namely: Mutonga and Low Grand Falls dams that will further combine forces with the current five dams in the Seven Forks to help in mitigating floods in those areas. This is the way to go.
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