The Yala River is a river in western Kenya, a tributary of Lake Victoria . It generally flows fast over a rocky bed through a wide valley before joining the Nzoia River to form the Yala Swamp on the border of Lake Victoria. The land along its course is mostly cultivated or used for grazing, with relatively few remnants of the original forest. Soil erosion is visible throughout the river basin, particularly in the lower parts. Projects are underway to exploit the river for hydroelectricity.
35-609: The Yala River rises in the Nandi Escarpment in the Rift Valley Province , Kenya. It flows west for 219 kilometres (136 mi) to its mouth on Lake Victoria in Siaya County , Kenya. It is one of the largest Kenyan rivers feeding Lake Victoria, with an average discharge of 27.4 cubic metres per second (970 cu ft/s). The river contributes about 5% of the annual inflow to Lake Victoria. The Yala River flows through
70-549: A bridge that carries the C27 coastal highway along the Goye causeway. The Yala River drainage basin covers 3,351 square kilometres (1,294 sq mi). An ecosystem management study of the Yala and Nzoia river basins issued a baseline report in 2008. It studied three representative 10 by 10 square kilometres (3.9 by 3.9 sq mi) blocks of land in the Yala basin. In all three blocks much of
105-593: A few large hills. Most of the population are Luo , but in some areas the people are mainly Luhya . About 43% of the land is used for crops, and 55% for grazing livestock. Livestock includes cows, bulls, chickens, goats and sheep. There are few trees, and widespread soil erosion. As of 2016 a feasibility study had been completed for development of the Nandi Forest dam to support irrigation, water supply and power generation. The power plant would have two 25 MW Pelton turbines and would supply 185 GWh annually. In April 2020 it
140-433: A global testing ground for 10–50 MW run-of-river technology . As of March 2010, there were 628 applications pending for new water licences solely for power generation, representing more than 750 potential points of river diversion. In undeveloped areas, new access roads and transmission lines can cause habitat fragmentation , allowing the introduction of invasive species. Run-of-the-river projects strongly depend on
175-471: A river's flow (up to 95% of mean annual discharge) through a pipe and/or tunnel leading to electricity-generating turbines, then return the water back to the river downstream. Run-of-the-river projects are dramatically different in design and appearance from conventional hydroelectric projects. Traditional hydroelectric dams store enormous quantities of water in reservoirs , sometimes flooding large tracts of land. In contrast, run-of-river projects do not have
210-566: A wide, mature valley that appears to have been rejuvenated during the tilting associated with the rifting movements of the mid- Pleistocene . It runs swiftly over a rocky bed, with a notable absence of alluvial flats and terraces. The main channel is about 30 metres (98 ft) wide, apart from the Yala Swamp. The river runs through the southeast of the Kakamega Forest , where it has a dramatic 20-metre (66 ft) waterfall. The Yala Swamp at
245-492: Is a type of hydroelectric generation plant whereby little or no water storage is provided. Run-of-the-river power plants may have no water storage at all or a limited amount of storage, in which case the storage reservoir is referred to as pondage . A plant without pondage is subject to seasonal river flows, so the plant will operate as an intermittent energy source . Conventional hydro uses reservoirs , which regulate water for flood control , dispatchable electrical power , and
280-417: Is considered an "unfirm" source of power: a run-of-the-river project has little or no capacity for energy storage and so cannot co-ordinate the output of electricity generation to match consumer demand. It thus generates much more power when seasonal river flows are high (spring freshet ), and depending on location, much less during drier summer months or frozen winter months. Depending on location and type,
315-501: Is generally used to cover exclusively short-term peak times electricity demand. Diversion Weir is also heavily dependent on the natural river flow. Similar to a regular dam, water is stored from lull periods to be used during peak-times. This allows for the pondage dams to provide for the regulation of daily and/or weekly flows depending on location. When developed with care to footprint size and location, run-of-the-river hydro projects can create sustainable energy minimizing impacts to
350-481: Is little subsistence agriculture. The cultivated land is interspersed with grasslands. Dairy production is important. 22% of the plots showed soil erosion in 2008. The Middle Yala Block in Vihiga District and Kakamega District contains mountainous highlands with many small streams, and held clusters of wetlands. There are preserved remnants of forest throughout the block used for cultural purposes, and logging in
385-441: Is rated at 1,853 MW. Some run-of-the-river projects are downstream of other dams and reservoirs. The reservoir was not built by the project but takes advantage of the water supplied by it. An example would be the 1995 1,436 MW La Grande-1 generating station . Previous upstream dams and reservoirs were part of the 1980s James Bay Project . There are also small and somewhat-mobile forms of a run-of-the-river power plants. One example
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#1733093299727420-653: Is the so-called electricity buoy , a small floating hydroelectric power plant . Like most buoys, it is anchored to the ground, in this case in a river. The energy within the moving water propels a power generator and thereby creates electricity. Prototypes by commercial producers are generating power on the Middle Rhine river in Germany and on the Danube river in Austria. The advantages and disadvantages of run-of-river dams depends on
455-915: The disadvantages associated with reservoirs and so cause fewer environmental impacts. The use of the term "run-of-the-river" for power projects varies around the world. Some may consider a project run-of-the-river if power is produced with no water storage, but limited storage is considered run-of-the-river by others. Developers may mislabel a project run-of-the-river to soothe public perception about its environmental or social effects. The European Network of Transmission System Operators for Electricity distinguishes run-of-the-river and pondage hydropower plants, which can hold enough water to allow generation for up to 24 hours (reservoir capacity / generating capacity ≤ 24 hours), from reservoir hydropower plants, which hold far more than 24 hours of generation without pumps. The Bureau of Indian Standards describes run-of-the-river hydroelectricity as: A power station utilizing
490-568: The Kaimosi forest in the southeast of the block. Most of the farms are overcropped, without traditional rotation and fallow periods. The farms are managed better in the north of the block, with more trees and hedges, while in the southern part steep slopes are cultivated with no conservation measures. About half the block shows evidence of soil erosion. The Lower Yala block in Kisumu District and Siaya District has low to medium gradient terrain with
525-508: The consistent flow of water, as they lack reservoirs and depend on the natural flow of rivers. Consequently, these projects are more vulnerable to climate change compared to storage-based projects. Short-term climate anomalies such as the El Niño Southern Oscillation (ENSO) [1] can significantly disrupt the flow and can have a profound impact on the operation of these projects. Thus, incorporating climate change considerations into
560-412: The electricity needed by consumers and industry. Moreover, run-of-the-river hydroelectric plants do not have reservoirs, thus eliminating the methane and carbon dioxide emissions caused by the decomposition of organic matter in the reservoir of a conventional hydroelectric dam. That is a particular advantage in tropical countries, where methane generation can be a problem. Without a reservoir, flooding of
595-555: The escarpment in the Lake Victoria catchment. The main scarp rises from around 1,700 to 2,000 metres (5,600 to 6,600 ft). The rugged terrain includes granite and volcanic rock. The Köppen climate classification is Am : Tropical monsoon climate. The Yala River rises below the escarpment. The scarp marks the boundary between the Nandi people to the east and the Luhya people to
630-563: The land was cultivated. Subsistence crops included maize , beans , sorghum , banana , cassava and sweet potato , while cash crops included tea , wheat and mango . The Upper Yala Block in the Uasin Gishu District includes Lake Lessos , one of the Yala River's main sources. The block has level terrain with medium gradient hills with shallow depressions. There are wetlands and small permanent streams. The farms are large and there
665-529: The mouth of the river covers about 175 square kilometres (68 sq mi) along the northern shore of Lake Victoria. The swamp contains 1,500 hectares (3,700 acres) Lake Kanyaboli , a freshwater deltaic wetland with an average depth of 3 metres (9.8 ft), which is fed by the floodwaters of the Nzoia and Yala rivers and by the backflow of water from Lake Victoria. The lake provides a refuge for several species of fish that are no longer present in Lake Victoria. In
700-401: The past the Yala River flowed through the eastern 20% of the Yala Swamp into Lake Kanyaboli, then into the main swamp, and then through a small gulf into Lake Victoria. Today the eastern part of the swamp has been drained, and the river flows directly into the 8,000 hectares (20,000 acres) main swamp. It is cut off from Lake Kanyaboli by a silt-clay dyke. Lake Kanyaboli now receives its water from
735-433: The plant will most likely have a lower head of water than from a dam, and will thus generate less power. The potential power at a site is a result of the head and flow of water. By damming a river, the head is available to generate power at the face of the dam. A dam may create a reservoir hundreds of kilometres long, but in run-of-the-river the head is usually delivered by a canal, pipe or tunnel constructed upstream of
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#1733093299727770-442: The power house. The cost of upstream construction makes a steep drop desirable, such as falls or rapids. Small, well-sited run-of-the-river projects can be developed with minimal environmental impacts. Larger projects have more environmental concerns. For fish-bearing rivers, a ladder may be required, and dissolved gases downstream may affect fish. In British Columbia , the mountainous terrain and wealth of big rivers have made it
805-547: The provision of fresh water for agriculture . Run-of-the-river, or ROR, hydroelectricity is considered ideal for streams or rivers that can sustain a minimum flow or those regulated by a lake or reservoir upstream. A small dam is usually built to create a headpond ensuring that there is enough water entering the penstock pipes that lead to the turbines , which are at a lower elevation. Projects with pondage, as opposed to those without pondage, can store water for daily load demands. In general, projects divert some or most of
840-497: The river and the adjacent lake. The watershed must also be rehabilitated to maintain farm productivity and to reduce erosion and sedimentation of the wetlands and river. A 2005 report noted changes in Lake Sare that threatened the lake ecosystem through eutrophication and pollution. It recommended an inclusive management plan for the Yala swamp complex to prevent further degradation of the ecosystem. As of 2019 BirdLife International scored
875-533: The river, deforestation and resulting river bank erosion, and sand extraction. Development potential includes irrigation and drainage projects in the lower and middle parts of the basin, hydroelectricity, wetlands products, eco-tourism and water sports tourism, and perhaps carbon sequestration . Conversion of the wetlands for crop production must be carefully managed to ensure environmental sustainability. Sufficient wetlands must be maintained to control erosion and improve water quality, which in turn affects fisheries in
910-581: The run of the river flows for generation of power with sufficient pondage for supplying water for meeting diurnal or weekly fluctuations of demand. In such stations, the normal course of the river is not materially altered. Many of the larger run-of-the-river projects have been designed to a scale and generating capacity rivaling some traditional hydroelectric dams. For example, the Beauharnois Hydroelectric Generating Station in Quebec
945-411: The surrounding catchment area and from back-seepage from the swamp. The river's gulf has been cut off from the lake by a culvert, which created the 500 hectares (1,200 acres) Lake Sare through back-flooding. Lake Sare, with its direct link to Lake Victoria, is important in preserving the cichlid fish fauna of Lake Victoria. The river water enters Lake Victoria from Lake Sare through a channel crossed by
980-417: The surrounding environment and nearby communities. Run-of-the-river harnesses the natural potential energy of water by eliminating the need to burn coal or natural gas to generate the electricity needed by consumers and industry. Advantages include: Like all hydro-electric power, run-of-the-river harnesses the natural potential energy of water by eliminating the need to burn coal or natural gas to generate
1015-514: The threat to the swamp complex as high, and was pessimistic about action being taken. Nandi Escarpment The Nandi Escarpment is an escarpment in Nandi County, Kenya. It marks the boundary between Kisumu and Nandi counties. It consists of numerous massive geological rocks ,one being Nandi rock. Monkeys and baboons are among common wildlife sightings. The escarpment lies on the border between Kakamega County and Nandi County . It defines
1050-406: The type, the following sections generally refer to Dam-Toe unless otherwise stated. These are listed in order of least impact to most impact, as well as (on average) requisite project size. Dam-toe has no flow regulation and utilizes the natural flow of the river to turn the turbines. Electricity generation is heavily dependent on river flow. Diversion Weir has very little flow regulation, which
1085-450: The upper part of the river does not take place. As a result, people remain living at or near the river and existing habitats are not flooded. Any pre-existing pattern of flooding will continue unaltered, which presents a flood risk to the facility and downstream areas. Due to their low impact, run-of-the-river dams can be implemented in existing irrigation dams with little to no change in the local fluvial ecosystem. Run-of-the-river power
Yala River - Misplaced Pages Continue
1120-432: The west. The 450 metres (1,480 ft) Sheu Morobi cliffs in the escarpment used to be used by old Nandi people to commit suicide so their family did not have to care for them. This was considered an honorable action, and would follow special rituals and a last meal. The name means "there we go forever". Run-of-the-river hydroelectricity Run-of-river hydroelectricity ( ROR ) or run-of-the-river hydroelectricity
1155-561: The western edge of the central highlands of Kenya. The escarpment lies between the North Nandi Forest to the east and the Kakamega Forest to the west. The North Nandi Forest is a strip of high-canopy forest about 30 kilometres (19 mi) long from north to south and 3 to 5 kilometres (1.9 to 3.1 mi) wide that runs along the rim of the escarpment. To the west the Kakamega Forest, a mid-altitude tropical rainforest, lies below
1190-471: Was announced that Tembo Power of Mauritius, along with Metier and WK Construction of South Africa had signed an agreement for development of a run-of-the-river hydroelectricity plant on the Yala River. The Kaptis Hydroelectric Power Station was to have a 15MW capacity and would be operational by 2022. The project would cost $ 30 million. The electricity would be fed to the grid operated by the state-owned Kenya Power and Lighting Company (KPLC). The power plant
1225-415: Was to be located near the town of Kakamega . A study of discharge data from 1950 to 2000 showed a general increase in discharge. This may be due to destruction of land cover, including indigenous forests. Yearly discharge of nutrients into the lake is about 1,000 tonnes of nitrogen and 102 tonnes of phosphorus . Threats to the river ecology include garbage from panning for minerals, oil spills in and near
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