Nairobi is in a unique club of capital cities located near the escarpment of the Great Rift Valley. This elevated location makes the Kenyan capital among the 10 highest in the world. Nairobi's location near the high escarpment also makes the city's environs the source of numerous rivers and streams. Unlike most of the global cities located on the banks of big rivers and having landmark bridges, Nairobi has a maze of smaller rivers and streams, collectively referred to as the Nairobi River Basin.

The main drainage systems of Kenya

A feature of the streams and rivers in Nairobi is that they all flow eastwards. The Western half of Nairobi marks the start of the ascent up the Rift Valley escarpment while the Eastern half is a flat plain. The rivers therefore flow by gravity to the East. All these rivers and streams join the main river of the Basin – the Nairobi River - near Dandora and Ruai which then proceeds to join the Athi River.

We will now embark on a brief journey that details the main rivers in Nairobi, their respective sources, the areas traversed by these rivers and their significant tributaries, starting with the Northern most going South.

1. Gathara-ini River

Gathara-ini is the river that lends its name to the Kasarani area. It starts off in Kiambu at Kanunga area where after a few kilometres, it lays its first claim to fame by being the river dammed at Paradise Lost Resort. It then crosses Kiambu Road at Thindigua and flows on the Northern side of the Windsor Golf and Country Club, past the Northern bypass and onto Kamiti road. Gathara-ini is the first big river one crosses from Roysambu on the way to Kamiti and Kahawa West.

Gathara-ini crosses Thika road as you approach Githurai from the city. Further downstream, it forms the boundary between Githurai Kimbo and the Northern side of Mwiki. It then flows through sparsely populated areas before crossing the Eastern bypass, where it joins the Nairobi river near the Ruai sewage treatment plant.

Gathara-ini is joined by its tributaries Kiu and Kamiti rivers that flow near Kahawa Barracks and Kenyatta University.

  1. Ruiruaka River

Ruiruaka river derives its name from the Kikuyu word Ruirwaaka meaning ‘the river of women’. Ruiruaka has two main tributaries, Ruaka and Karura rivers, which flow side by side from their origin in Limuru to Ruaraka, Thika road.

Ruaka river flows East parallel to Limuru road and is first noticeable at Ruaka town where It lends its name to the eponymous town and falls. The river flows past Two Rivers Mall (was the Mall named after the nearby Ruaka and Karura rivers?) and Rosslyn Riviera onto Runda. Ruaka river then flows along the northern sections of Karura forest before emerging on Kiambu road near Ridgeways.

Karura river flows from Limuru adjacent to the Red Hill road, snakes its way across Rosslyn estate and crosses Limuru road along the river valley between Village Market and the Australian Embassy. Karura river then flows through Gigiri before traversing Karura forest, splashing down the splendid Karura falls and emerging on Kiambu road after the CID headquarters.

Ruaka and the Karura rivers confluence adjacent to Thika Highway, giving birth to Ruiruaka river. Ruaraka estate is named after the river and was the site of the first brewery in Kenya, the availability of fresh water no doubt influencing the location. EABL later set up their headquarter in this vicinity. The river then forms a distinction between EABL-Ngumba area and Baba Ndogo. Further downstream it flows in the Lucky Summer area and joins the Nairobi River at Dandora phase 5.

3. Mathari, Getathuru and Kibagare Rivers

Like Ruaka and Karura, Getathuru and Mathari rivers have their origin in Limuru and flow adjacent to each other before joining up. Getathuru flows north of Wangige town and runs parallel to the Getathuru road. It flows past UoN School of Business, through Kitusuru estate (named after Getathuru?) and flows into Sigiria-Karura forest near the Kitisuru road and Peponi road junction. Getathuru forms the southern boundary of Sigiria forest and cuts across the forest to emerge across Kiambu road near Muthaiga Golf course. Getathuru crosses Thika road near NYS headquarters and flows into Mathari slums where it is joined by Mathari river.

The main tributary of the three, Mathari River flows upstream as Gataara river in the Kabete area. It forms a natural boundary between Loresho and Lower Kabete. Mathari river is dammed at Kabete dam. It then flows adjacent to Lower Kabete road and cuts across the intersection between the Westlands-Red Hill bypass. Mathari River then flows through Spring Valley, north of Highridge and Deep Sea Slum before cutting across Limuru road between Parklands and Muthaiga. It then flows south of Muthaiga road and is joined by Kibagare river at City Park near the Kiambu road junction.

Kibagare river springs out of the ground at KALRO Headquarters in Kangemi and can be seen from Waiyaki Way. About a kilometre from the spring, the river is dammed at Kangemi dam.

Kibagare river then flows past Loresho, Kibagare estate, Nairobi School, through Kyuna estate and past the Red Hill road to Spring Valley. Spring Valley estate might have been named after the river valley that traverses the neighborhood. Past Spring Valley, Kibagare river is tunneled along Mwanzi road. It is along this section that the Nakumatt Ukay building was located. The building was demolished in 2018 when the Nairobi River Taskforce moved to reclaim riparian land.

Kibagare river then flows under the Ring road Parklands and across Oshwal Center. The river is tunneled along sections of the community center. Past Oshwal, the river river flows near Parklands first avenue and enters City Park near Prof. Wangari Maathai road. Kibagare then flows across City Park, providing a lifeline to the Park before joining up with Mathari river.

The twin Mathari-Kibagare link up with Getathuru in Mathari slums from where it is named Mathari river. It continues to flow and forms a boundary between Huruma and Mathari estates. After cutting across Outering road, Mathari river forms a boundary between Kariobangi North and Baba Ndogo. It passes other major slums of Korogocho and Ngomongo before joining Nairobi River at Dandora phase 4.

The Mathari valley has the second largest informal settlement in Kenya. A distinct feature of the key Nairobi slums is that they are located along river valleys. Apart from Mathari slum along the Mathari River, there is Korogocho slum along the same river, Kibera slum along the Ngong River and Mukuru slums also along the Ngong River, among others.

4. Nairobi River

Nairobi River, the main tributary of the Nairobi River Basin, starts from the Ondiri swamp in Kikuyu. The swamp was the first source of piped water for Nairobi as water used to flow through the pipes by gravity to the city. From Kikuyu, the river flows through Dagoretti area adjacent to Kikuyu road and crosses Naivasha road between near Kangemi. It then flows south of Mountain View estate and Kangemi, forming a natural boundary between Kangemi and Kawangware before emerging at James Gichuru Road near Muthangari Polce Station.

Nairobi River then flows between Muthangari and Riverside to emerge across Ring Road Westlands between Riverside junction and the Rhapta road junction. It continues to flow behind Consolata School and cuts across the road at Chiromo, before crossing Waiyaki way at Museum Hill. At Chiromo area, Nairobi River is joined by its major tributary - the Kirichwa River - which emerges from the Dagoretti area and flows through Riruta, Thompson Estate, Kilimani, Kileleshwa and Arboretum.

The confluence area of these two rivers was named ‘Chiromo’ which means ‘joining of two rivers’ in a Malawian language. The area was so named by Ewart Grogan, one of the early colonial settlers, who saw similarities between the area and a village he had travelled through in Southern Malawi that went by the same name.

Nairobi River now flows besides Kipande Road on one side and Kijabe Street on the other. It flows through John Michuki Park and emerges at Globe Cinema roundabout. Nairobi river then flows through Ngara, Kamukunji, Gikomba, Majengo and Shauri Moyo, forming a boundary between the latter two. The river then crosses Eastleigh First Avenue near Section 3 area and forms the southern boundary of Eastleigh Air Base.

Nairobi river also flows near or through Bahati, Jerusalem, Uhuru and Buruburu estates. The Kiambui slums occupy a small stretch of land between Moi Air Base and the river. the river then crosses Outering Road and cuts through Kariobangi South estate. On your way to Dandora, Nairobi River cuts across Komarock Road and at this stage, the river is about to join with the Mathari River. Nairobi River then flows next to Dandora Phase 1, past the vast Dandora dumpsite and links up with the Mathari river at Dandora Phase 4.

Further downstream at Dandora phase 5, Nairobi River is joined by Ruiruaka River and becomes one big river. From Dandora, it is bordered to the North by Mwiki and to the South by Njiru, an area sparsely populated because of the extensive quarrying that takes place there. At New Njiru, Nairobi River is joined by another of the major Nairobi rivers, the Ngong River. The bigger Nairobi River crosses the Eastern by pass a short distance North of the Kagundo road intersection and flows next to the Nairobi Sewage treatment works at Ruai where treated Nairobi waste water is discharged into the river. It is also joined by the Gatharaini at this site and further upstream, the Kiu river. Nairobi River then joins Athi River after this.

5. Ngong River

Ngong River originates from the Kibiku forest, South of Ngong hills. At this point, it is known as Motoine river. It flows besides the Southern bypass between Dagoretti and Karen. The river is seen near the Ngong Road intersection with the bypass and it is the river one crosses from Lenana School on your way to Karen. Ngong River (still named Motoine at this stage) then flows through the Ngong Road Forest, emerging at Kibera where it is joined by other small streams. It flows through Kibera and is dammed at Nairobi Dam. At one point, the dam served the water needs of Nairobians and hosted various water sports, evidenced by the Sailors Club on the Langata side of the dam.

Past Nairobi Dam, the river adopts the name Ngong River and flows next to Highrise, cutting across Mbagathi road near the AP Camp. It crosses Langata Road near TMall and proceeds through Nairobi West where it can be seen near West mall. The river then flows through South C and emerges at Mombasa road next to the ICC Church. Past Mombasa Road, Ngong River flows into South B and passes near Mater Hospital. It flows for several kilometres through Industrial Area and is crossed by both Likoni road near Winners Chapel and Enterprise road from Tetra pack on the way to General Motors.

Ngong river at Outering road after passing through Kibera, Mukuru and Industrial Area

Along this stretch, the Ngong River valley plays host to Mukuru, Fuata Nyayo and Sinai slums. It emerges at Outering road near Tassia and forms the boundary between Donholm and Embakasi estates. Ngong River then flows Northwards to Kayole-Soweto area and crosses Kangundo road, joining Nairobi river at New Njiru. At this point, Ngong River is the most polluted river in the country and cannot support any living organisms, including bacteria, as a result of navigating 12 kilometres through the Nairobi's Industrial Area where chemical waste is discharged into the river.

6. Mbagathi River and Athi River

Mbagathi River starts out at Athi spring (so named as it is considered the starting point of the Athi river) in the Kibiku forest area of Ngong. It crosses Ngong Road at the Mbagathi bridge, past Karen Shopping Centre on your way to Ngong. It flows through Karen and it is the river that passes through Oloolua Forest. The cave system within the Ngong River valley at Oloolua is famed for being Mau Mau hideouts during the war for independence. Smaller streams from the Ngong Hills drain into Mbagathi River in Karen and it is a significant river by the time it crosses Magadi Road in Ongata Rongai near Multi Media University.

Mbagathi river upstream at Oloolua Nature Trail, Karen.

Mbagathi River flows past Rongai and goes on to form the Southern boundary of the Nairobi National Park. Ngong Hills is a major catchment area and as such, many streams flow down from the Hills through Karen and further downstream into the National Park. Mbagathi is joined by one such stream, the Kandisi river near Ole Kasasi in Rongai. The streams within the Park all flow to join the Mbagathi River. The biggest of these streams is the Mokoyeti which is the river that crosses Langata Road between Galleria Shopping Mall and the Langata Cemetery.

One of the many streams in the Nairobi National Park that flow southwards to join the Mbagathi River
One of the many streams in the Nairobi National Park that flow southwards to join the Mbagathi River

Past the National Park, Mbagathi River emerges near Athi River town and cuts across Namanga Road. The new name for the river at this point becomes Athi River, having been joined by Stony Athi river that flows from Isinya. The river changes direction from Southwards to the North East as a natural barrier to the gravitational flow of the river is presented by the Lukenya Hills. Athi River then flows North Eastwards and is joined later on by the rivers from the Nairobi River Basin.

Satellite Image of Nairobi: 1. Mbagathi River at the Southern border of the Park 2. Ngong River 3. Nairobi River 4. Point where Ngong River joins the Nairobi River in Dandora 5. Ruai Sewage Treatment Plant 6. Athi River flowing round Mt. Kilimambogo
Satellite Image of Nairobi:
1. Mbagathi River at the Southern border of the Park
2. Ngong River
3. Nairobi River
4. Point where Ngong River joins the Nairobi River in Dandora
5. Ruai Sewage Treatment Plant
6. Athi River flowing round Mt. Kilimambogo

Having joined the Athi River, the Nairobi River Basin ceases to exist. Athi River, a big river by this stage, flows round Mt. Kilimambogo through Ukambani area and 600 Kilometres later, the journey ends at the Indian Ocean near Malindi.

Athi river flowing near the eponymous town.
Fourteen Falls
Athi river at Sabaki bridge, about a kilometer near mouth at Indian ocean