Up and down the mountain
Let's unfold the map and take a look at Uganda's topography. Let's begin our brief study with the lowlands (600-900 m above sea level): these represent around 9% of the country's surface area and are located in the west and north-west of the country, in the graben (collapse trough) of the western rift. The lowest altitude (614 m) and warmest temperatures are recorded here. Now we come to the plateau (900 to 1,500 m), which accounts for 85% of the country's surface area. Composed of arable and grazing land, it is geomorphologically and climatically heterogeneous. The thorn-strewn savannahs of the north and northeast - where stubby granite inselbergs protrude from far and wide - can be distinguished from the more fertile peneplains of the center and south, dotted with swamps and irrigated by lakes (Victoria, Kyoga, Wamala, Bisina...) and rivers (Katonga, Kafu, Nil, Ssezibwa...). Let's continue our topographical survey of the highlands (1,500 to 2,500 m). Covering approximately 5% of the country, the highlands are mostly located in the south-west. The highly watered Kigezi, bordered by the DRC and Rwanda, is the most famous of these highlands. With its lush hills covered with small plots of cultivated land, its superb forests (Bwindi, Echuya...), its magnificent bodies of water (Bunyonyi, Mutanda...) and with Virunga as a backdrop, it is sometimes nicknamed "the Switzerland of Africa". Less spectacular are the Bushenyi Hills (between Ibanda and Bushenyi), the Isingiro Hills (south-west of Lake Mburo) and the Kitara Uplands (east and south-east of Fort Portal). Finally, let's climb the mountains (from 2,500 to 5,100 m), or 1% of the Ugandan state's surface area. Located in the western and eastern marches of the country, they are a hiker's delight. The roof of the country, Peak Margherita (5,109 m), dominates the Rwenzori peaks, a very young massif (3 million years old) born of the surrection of crystalline rocks. By contrast, the isolated, extinct stratovolcano of Mount Elgon (4,321 m) is at least 24 million years old. More generally, the Rwenzori peaks stand out, in terms of orogeny, from other mountains over 3,000 metres (Mt. Moroto, Mt. Kadam, Muhavura, Gahinga and Sabinyo) are the result of successive volcanic eruptions (as the basalts of Mgahinga National Park remind us) that predate (20 million years for Mount Moroto) or postdate (between 2.6 million years and 130,000 years for the Ugandan part of Virunga) the formation of the chain dominated by Peak Margherita.
And in the middle flows a river
A significant portion of the country is covered, temporarily or permanently, by water. For example, Lake Victoria, the largest body of fresh water in Africa (nearly 70,000 km2), bathes southern Uganda. It was named in the mid-19th century by the British explorer John Speke in honour of his sovereign. On the pontoon, Lakes Albert (5,300 km²) and Edward (2,300 km²), which cross the Ugandan-Congolese border and are part of the African Great Lakes, as well as Lake George, which is much smaller than the former (250 km²), were also named in honour of members of the British royal family by explorers from the United Kingdom (the first by Samuel Baker, the second and third by Henry Stanley). Located in the middle of the country and fed by the Nile, Lake Kyoga also has a large surface area (1,720 km²). The Nile, let's talk about it! The river, some 6,700 km long, flows out of Lake Victoria (1,134 metres above sea level) at Jinja. Under the name of the Victoria Nile, it joins - after having played with three dams (Owen Falls, Bujagali and Isimba) which release its waters at a rate of 650 to 1,500m3/s- the said Lake Kyoga (1,033 m) which constitutes a navigable portion. Then, downstream, come Masindi Port (a small town that was once one of the nerve centres of regional trade flows), the Karuma hydroelectric dam and, within the eponymous park, the super-powerful Murchison Falls (here, 300m3 of water rushes per second through a gap less than ten metres wide: guaranteed Venturi effect!) The Victoria Nile then follows its course to Lake Albert (620 metres above sea level) where it becomes, as is only natural, the Albert Nile. From here, it has 210 km to go, through swampy terrain, to the South Sudanese border (614 metres above sea level, the lowest point in the country). In short, before becoming the Bahr el-Jebel in Southern Sudan, the Nile in Uganda meanders for 540 km, slopes 520 metres and spreads fluvial alluvium along its entire length.
About the Rift
Uganda is nestled between the eastern and western branches of the East African Rift, a fault, a gap, a break (such are the meanings of the English word rift) that runs for several thousand kilometers from Mozambique to the Red Sea and the Gulf of Aden. The Rift Valley is the result of intense tectonic activity over the past 30 million years, with volcanoes, depressions and large lakes dotting the landscape. This fault should one day separate the African (on which Uganda and the Western Rift are located) and Somali plates. Within the "Pearl of Africa", Mount Elgon, which margins the Eastern Rift, is evidence of the age of this East African fault system. However, it is towards the Western Rift (or Albertine Rift) that one must look to see the geological dynamism of the region. Here, the effects of the tectonic faults (the main one and the secondary ones) are prominent: the presence of a graben (depression) at the bottom of which flows the Semliki River and the Edward and Albert lakes lie, horsts (blocks raised between two grabens) symbolized by the Rwenzori, young mountains (Virunga) and hot springs (Rwagimba, Sempaya...). The seismicity and the volcanic activity of the area are also perceptible: the Nyiragongo and Nyamuragira volcanoes (DRC), 30 km from the Ugandan border, have erupted several times since the beginning of the 21st century..
