Malewa River

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Malewa River
Physical characteristics
Mouth  
 • coordinates
 0°43′29″S36°21′12″E / 0.724778°S 36.353288°E / -0.724778; 36.353288 Coordinates: 0°43′29″S36°21′12″E / 0.724778°S 36.353288°E / -0.724778; 36.353288
Basin size1,730 square kilometres (670 sq mi)
Basin features
Tributaries 
 • left Turasha
 • right Wanjohi

The Malewa River rises in the western slopes of the Aberdare Range in Kenya and flows south and west into Lake Naivasha in the Great Rift Valley. Lake Naivasha is an important source of water in a semi-arid environment, and supports export-oriented horticulture and floriculture businesses as well as tourism. Malewa River water quality has deteriorated because of more human activities in the upper catchment. Long-term effects of this on the percentage of rainfall getting into Lake Naivasha are not clear. Possibly in low-rainfall years the percentage will drop because of water abstraction, while in high-rainfall years the percentage will go up because of cultivated soils having a lower water-holding capacity and the introduction of more 100% runoff surfaces like tarmac roads and iron sheets, etc.

Contents

Catchment

The Malewa River catchment of 1,730 square kilometres (670 sq mi) provides about 90% of the water flowing into Lake Naivasha, with most of the remainder coming from the Gilgil River. [1] The headwaters of the main channel of the Malewa originate at an elevation of 3,700 metres (12,100 ft) in the Nyandarua (Aberdare) mountains. Its tributary the Wanjohi is fed by several small rivers running from the slopes of the Aberdares. [2] Other tributaries are the Turasha, Simba, Nyairoko and Ol Kalou. [3] The rivers in the Malewa basin are relatively shallow but are all perennial. [2]

The Aberdare range receives about 1,200 millimetres (47 in) of rain annually and has large areas of dense forest. The highlands drained by the Malewa are volcanic and contribute sodium and calcium to the water through chemical weathering of the rocks. Sulphate in the water comes from the atmosphere. [4] The floor of the Rift Valley gets just 600 millimetres (24 in) each year and is mainly covered by scrub, with some bare soil. Rainfall peaks between April and June and again in October and November. Erosion is highest in these months. [5]

Land use

The Malewa river is fed by streams that run through the Kinangop Plateau. At one time the plateau was almost completely covered in tussocky grassland with very few trees. The stream valleys had many tussocky bogs. The plateau has been settled by Kikuyu farmers since the 1960s. They have ploughed much of the land to grow maize, wheat, cabbage and potatoes. The wetlands have mostly been drained. [6] Where drainage has not been deliberate, the trees planted for poles and firewood have absorbed the water. The trend is towards more intensive cultivation of food crops and cash crops. [7]

Issues

The river is threatened by deforestation and siltation, increasing diversion of water for irrigation, and pollution by fertilizers and pesticides. [8] In August 1997 sediment-laden plumes of Malewa river water extended about 500 metres (1,600 ft) into Lake Naivasha. [2] Access to natural resources and markets is not equitable in the region. Water conflict is common and poverty widespread. Improvements to resource management practices could cause major improvements in reducing pollution and erosion. [9]

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Geography of Tanzania

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Lake Naivasha it a town now occupied with many tribes

Lake Naivasha is a freshwater lake in Kenya, outside the town of Naivasha in Nakuru County, which lies north west of Nairobi. It is part of the Great Rift Valley. The name derives from the local Maasai name Nai'posha, meaning "rough water" because of the sudden storms which can arise.

African Great Lakes Series of lakes in the Rift Valley

The African Great Lakes are a series of lakes constituting the part of the Rift Valley lakes in and around the East African Rift. They include Lake Victoria, the second-largest fresh water lake in the world by area, Lake Tanganyika, the world's second-largest freshwater lake by volume and depth, and Lake Malawi, the world's eighth-largest fresh water lake by area. Collectively, they contain 31,000 km3 of water, which is more than either Lake Baikal or the North American Great Lakes. This total constitutes about 25% of the planet's unfrozen surface fresh water. The large rift lakes of Africa are the ancient home of great biodiversity, and 10% of the world's fish species live in this region.

Aberdare Range Mountain range in Kenya

The Aberdare Range is a 160 km long mountain range of upland, north of Kenya's capital Nairobi with an average elevation of 3,500 metres (11,480 ft). It is located in Nyandarua County, west central Kenya, northeast of Naivasha and Gilgil and just south of the Equator. The mountain range is called Nyandarua among the Agikuyu people in whose territory this forest and mountain range is located. The name Nyandarua comes from the Kikuyu word rwandarua meaning a drying hide, due to the distinctive fold of its silhouette.

The Kipengere Range, also known as the Livingstone Mountains, lies in southwest Tanzania at the northern end of Lake Malawi. Near Lake Malawi they are known as the Kinga Mountains. It is a plateau-like ridge of mountains running southeastwards from the basin of the Great Ruaha River in the north to that of the Ruhuhu River in the south, and forms part of the eastern escarpment of the East African Rift. The range is mostly clad in montane grasslands, renowned for their botanical diversity and displays of flowers, with montane evergreen forests mostly in stream valleys.

Semliki River

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Phrynobatrachus kinangopensis is a species of frog in the family Phrynobatrachidae. It is endemic to the Kenyan Highlands east of the Great Rift Valley. Both the scientific name and its common names, Kinangop river frog and Kinangop puddle frog, refer to its type locality, Mount Kinangop.

The Southern Highlands is a highland region in southwestern Tanzania, at the northern end of Lake Malawi. The highlands include portions of Mbeya, Njombe, Rukwa, Ruvuma, and Songwe regions, bordering Malawi, Mozambique, and Zambia. Mbeya is the largest city in the highlands.

Deforestation in Kenya

Kenya’s forests are fragmented across the country, combined together the forests expand to over 37 million hectares. Out of those 37 million hectares, 2.1 million are woodlands, 24.8 million are bush lands and 10.7 are wooded grasslands. Kenya’s forests are important at a global level as they host 1847 species of amphibians, birds, mammals, and reptiles of which 4% are only found in Kenya. Beyond its fauna, Kenya’s forest also hosts 6505 types of vascular plants, with 4.1% only being found in Kenya. Today Kenya faces high rates of deforestation which endanger both its fauna and flora. It has been estimated that since Kenya’s independence in 1963 the forest has dropped from covering 10% of the nation to 6%, losing approximately 12,000 hectares annually. These levels of deforestation have impacted Kenya as they rely on the forest for the storage of rainwater, the prevention of flooding, the fertility of the soil, and the regulation of climate conditions. The World War II period and its aftermath made it clear to British colonial administration that reform was needed to sustain Kenyan forests. One of the first steps for conservation jiiijjjtook place with the 1941 revision of the Forest Ordinance that passed legislation to create forest reserves and create a committee with professionals on matters of conservation. By 1950 the forest department had gained control of 100,000 acres, but it had a difficult time sustaining the conservation of these areas; it required meaningful policy to meet the constant attention these areas needed.

Great Rift Valley, Kenya Part of an intra-continental ridge system that runs through Kenya

The Great Rift Valley is part of an intra-continental ridge system that runs through Kenya from north to south. It is part of the Gregory Rift, the eastern branch of the East African Rift, which starts in Tanzania to the south and continues northward into Ethiopia. It was formed on the "Kenyan Dome" a geographical upwelling created by the interactions of three major tectonics: the Arabian, Nubian, and Somalian plates. In the past, it was seen as part of a "Great Rift Valley" that ran from Madagascar to Syria. Most of the valley falls within the former Rift Valley Province.

Mount Kipipiri

Mount Kipipiri is an isolated volcano in the Wanjohi Valley, on the Kinangop Plateau near to the Aberdare Range. It is about 20 miles (32 km) northeast of Lake Naivasha, which is visible from the summit. Wildlife includes Colobus and Sykes monkeys, elephants and buffalo and abundant birdlife. The name of the mountain means "butterfly" in the Gikuyu language, a reference to its profile from a distance.

Kinangop Plateau

The Kinangop Plateau is a region in Kenya that lies between the Kenyan Rift Valley to the west and the Aberdare Range to the east. It takes its name from Kinangop Mountain, which rises in the Aberdares to the east.

Mount Kinangop

Mount Kinangop is a mountain in the southern Aberdare Range about 100 miles (160 km) north of Nairobi, Kenya. It is within the Aberdare National Park.

The Gilgil River drains part of the floor of the Great Rift Valley, Kenya and the plateau to the east of the valley, flowing from the north into Lake Naivasha. The river runs to the east of the town of Gilgil, which is on the height of land between the Lake Naivasha and Lake Elmenteita basins.

The Turasha River is a major tributary of the Malewa River, which feeds Lake Naivasha in the Great Rift Valley of Kenya.

Perkerra River

The Perkerra River is a river in the Great Rift Valley in Kenya that feeds the freshwater Lake Baringo. It is the only perennial river in the arid and semi-arid lands of the Baringo County. The Perkerra river supplies water to the Perkerra Irrigation Scheme in the Jemps flats near Marigat Township, just south of the lake.

The Southern Eastern Rift is a freshwater ecoregion in Kenya and Tanzania.

Yala River

The Yala River is a river of 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.

References

  1. ↑ Gherardi 2007, p. 93.
  2. 1 2 3 Harper 2003, p. 16.
  3. ↑ Harper 2003, p. 17.
  4. ↑ Young 1996, p. 142.
  5. ↑ Hamududu 1998.
  6. ↑ Birdlife International.
  7. ↑ Darwin Initiative 2006.
  8. ↑ Lake Naivasha - Malewa.
  9. ↑ Ogweno 2009.

Sources

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