Mara River Kenya: Source, Course and What Lives in It
The Mara is the only river in the Masai Mara that flows all year. It rises in the Mau Forest, runs 395 km through Kenya and Tanzania, and empties into Lake Victoria. It holds the reserve’s hippos and big crocodiles, forms the eastern edge of the Mara Triangle, and is the stage for the migration crossings.
What This Guide Covers
- Where the river starts and where it goes
- The river inside the reserve
- Hippos, crocodiles and everything else that lives in it
- The best places to see the river on a game drive
- Floods, low water and what each season looks like
- Why the river is in trouble upstream
- The crossings, in short
- Questions guests ask
Where the river starts and where it goes
If you stand on the bank at the New Mara Bridge in August and watch the brown water go past, you are looking at rain that fell on the Mau Forest in April. The river begins up there, on the western wall of the Rift Valley at close to 2,900 metres, in cold, wet forest and swamp that pulls moisture off Lake Victoria. Two streams carry it down. The Amala and the Nyangores wind through the tea estates and smallholdings around Bomet, then meet in the farmland to the south, and from that point the river is called the Mara.
It drops onto the Loita Plains, enters the reserve from the north, collects the Talek River about halfway down, then the seasonal Sand River near the Tanzanian border, and carries on through the Serengeti. It finishes at Mara Bay on the Tanzanian shore of Lake Victoria, near Musoma. Source to mouth is about 395 km, and roughly two thirds of the catchment is on the Kenyan side.
I mention the Mau because guests often assume the Mara is fed by rain on the reserve. It isn’t, or not much. When the forest upstream is cut or the farms pump harder, the river we drive beside drops, and it has been dropping for years.
Key Facts About the Mara River
| Feature / Detail | Description |
| Length | About 395 km |
| Source | Mau Forest, Kenya (roughly 2,900 m above sea level) |
| Main Tributaries | Amala, Nyangores, Talek, Sand River |
| Mouth | Mara Bay, Lake Victoria, Tanzania |
| Catchment Area | About 13,750 sq km (shared by Kenya and Tanzania) |
| Course Through Reserve | Enters from the north, swings southwest along the Mara Triangle |
| Year-Round Flow | Yes, it is the only perennial river in the Mara-Serengeti ecosystem |
The river inside the reserve
The Mara runs for roughly 60 km inside the reserve before it crosses into Tanzania, and for most of that distance it is the line between the two halves of the Masai Mara. West of the water, up against the Oloololo Escarpment, is the Mara Triangle, run by the Mara Conservancy. East of it is the Narok sector, which has most of the camps and nearly all of the vehicles.
You cross from one side to the other at the New Mara Bridge, which older guides still call Purungat, in the far south near the border. There is a ranger post, and the rangers will walk you down to the water for a few minutes. It is the one place in the reserve where you can stand on the bank with hippos in front of you, and I stop there on every drive into the Triangle.
Away from the bridge the river is wrapped in a strip of forest: fig trees, wild date palms, greenheart, and undergrowth so thick you can be ten metres from the water and not see it. Nothing else in the reserve looks like it. Leopards hunt in it. Elephants come down through it in the afternoon. Bushbuck, waterbuck and vervets never leave it. On a slow day I would rather drive the forest edge than the open plain, because sooner or later everything has to come to the water.
Hippos, crocodiles and everything else that lives in it
The Mara carries one of the heaviest hippo populations in East Africa. They sit in pods of ten to forty in the deep bends, spend the day submerged and arguing, and walk out at dusk to graze, sometimes several kilometres from the river. If your tent is near the water you will hear them all night, and most guests say they slept better for it. There is more on them in our hippo guide.
The crocodiles are the other full-time residents, and the Mara’s are big. Males over four metres are not unusual below the Serena bends. For most of the year they lie on the sandbanks doing nothing, so guests drive past in March without a second glance and then watch the same animals take wildebeest in August. Our crocodile guide explains where to look.
Then there is everything else. Giant kingfishers and fish eagles working the pools. Hamerkops. Big gatherings of open-billed storks on the sandbars in the dry season. Monitor lizards, two metres long, sunning on the banks. Elephant families bathing in the shallows between the Serena and Oloololo Gate in the late afternoon. And, once or twice a year if we are very lucky, otters at first light in the quiet Triangle pools.
The best places to see the river on a game drive
Most visitors see the Mara at a crossing point and nowhere else, which is a shame, because the quiet stretches are better for everything except wildebeest. These are the places I take people.
New Mara Bridge. The hippo walk, the crocodile sandbanks just upstream, and the only chance to get out beside the water. Do it on the day you drive into the Triangle.
Below Mara Serena. The track along the Triangle bank gives you long views over the bends, a hippo pool every kilometre or so, and elephants crossing in the afternoon. The light is best from this side in the morning.
The Governors’ stretch. The river loops past the Governors’ camps on the Narok side. The forest here is the best leopard country in the northern reserve, and the crossing points called Main and Cul-de-Sac are in this section.
Lookout Hill. A short climb for the only raised view of the river’s course across the plains. Worth it for photographs, and for understanding how the herds funnel towards the water.
The Sand River confluence. Down in the south east near Sand River Gate, where the Sand River joins the Mara. Hardly any vehicles and some of the best game viewing in late June and July.
A handful of camps sit right on the bank: Governors’ Camp, Little Governors’, Mara Serena and Entim on the Mara, and Mara Intrepids on the Talek. If hearing hippos from your bed is part of the plan, say so when you ask for a quote and we will keep you by the water.
Floods, low water and what each season looks like
The river never stops, but it is a different river in May and in February.
The long rains, March to May, fill it to the lip of the banks and some years over them. In the first week of May 2024, after days of storms, the Talek and the Mara both broke their banks, camps along the river went under, and guests were flown out by helicopter. Reserve roads were cut for days. That was an extreme year, but smaller floods come most Aprils, which is why we steer anyone travelling in April or May towards camps on higher ground.
From June the water falls. By late July the sandbanks are out, the crocodiles are lying in the open, and the river is at the depth the wildebeest can wade and swim. It holds there through the short rains in November, which top it up without flooding. January and February are the low months, and in a dry year the upper river shrinks to a string of pools.
For planning, low water from July to October is what makes the crossings possible and the hippo pools easy to find. High water in April and May makes the river dramatic but keeps you further from it. Our best time to visit guide weighs this against everything else.
Why the river is in trouble upstream
The Mara is a small river carrying a very large ecosystem, and the upper catchment is not in good health.
The Mau Forest, where it starts, has lost a big share of its trees since the 1990s to settlement and farming. Less forest means less water held in the soil and let out slowly through the dry season, and more silt washed down with every storm. The Amala and the Nyangores are pumped hard for irrigation before they even meet. Sand is dug from the lower river in Kenya, and there have been proposals for dams on the Tanzanian side. In the worst droughts the flow at the border has fallen to a fraction of what the older rangers remember.
Why it matters goes beyond scenery. In 2017 a team of scientists published a study in the Proceedings of the National Academy of Sciences that counted the wildebeest drowning in the Mara during the crossings. The average was 6,250 animals a year, about 1,100 tonnes of carcasses, which feed the crocodiles, the storks, the vultures and the fish for months afterwards and put nutrients into the river itself. Take away the river and you take away the migration. The paper is at pnas.org.
On the ground, the Mara Conservancy manages the Triangle side and publishes monthly reports on water levels and wildlife, and the Mara River Water Users Association works with the farms upstream. Part of every park fee ends up in that work. If you ever wonder what the fee pays for, this is a good part of the answer.
The crossings, in short
From July to October the wildebeest and zebra cross the Mara and the Talek again and again as they move between the Serengeti, the reserve and the conservancies. The crossings deserve their own page, with the crossing points, the timing and what the long wait is really like, so we wrote one rather than bury it here. It is our Mara River crossing guide. The migration hub covers the whole season.
Questions guests ask
Does the Mara River mark the Kenya-Tanzania border?
No. The river crosses the border rather than running along it. The border is a line of white concrete beacons south of Sand River Gate. Inside Kenya the river is the boundary between the Mara Triangle and the Narok sector, which is usually what people mean.
Can I swim in the Mara River?
No. Hippos kill more people in Africa than any other large mammal, and the crocodiles here are among the biggest in the country. The only place to approach the water on foot is the escorted walk at New Mara Bridge, and even there you stay on the bank.
Is it worth seeing the river outside migration season?
Yes, and in some ways it is better. From November to June the crossing points are empty, the hippo pools are easy to reach, and the riverine forest is where the leopards are. A river drive in February with no other vehicle in sight is one of the best days the reserve offers.
Is there a boat safari on the Mara River?
No. It is too shallow, too full of hippos and too protected for boats inside the reserve. Kenya’s boat trips are on Lake Naivasha, which we pair with the Mara on our Mara and Naivasha itineraries.
Which camps are on the river?
On the Mara itself, the Governors’ camps, Mara Serena, Entim, Sala’s and the Triangle camps. On the Talek, Mara Intrepids, Fig Tree and Mara Expedition. Our camps guide has the full list with rates.
How do I plan a trip around the river?
Tell us whether you want the crossings, the quiet river, or both. For crossings, a 5 day safari in August or September with two full days at the water. For the river itself, any three or four day trip between November and March with a camp on the bank. Send your dates and we will reply with an itemised quote within 24 hours.
Written by David Njunge, a TRA-licensed safari guide who has worked the Mara River for over 10 years. Edited by Cess Wambui. Last updated October 2026.
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