Mweru means 'lake' in a number of Bantu languages, so it is often referred to as just 'Mweru'.
The Luapula forms a swampy delta almost as wide as the southern end of the lake. In a number of respects the lower river and lake can be treated as one entity. For a lake in a region with pronounced wet and dry seasons, Mweru does not change much in level and area. The annual fluctuation in level is 1.7m, with seasonal highs in May and lows in January. This is partly because the Luapula drains out of the Bangweulu Swamps and floodplain which tend to regulate the water flow, absorbing the annual flood and releasing it slowly, and partly because Mweru's outlet, the Luvua, drops quickly and flows swiftly, without vegetation to block it. A rise in Mweru is quickly offset by a faster flow down the Luvua.
Mweru's average length is 118 km and its average width is 45 km, with its long axis oriented northeast-southwest. Its elevation is 917 m, quite a bit higher than Tanganyika (763 m). It is a rift valley lake lying in the Lake Mweru-Luapula graben, which is a branch of the Great Rift Valley. The western shore of the lake in DR Congo exhibits the steep escarpment typical of a rift valley lake, rising to the Kundelungu Mountains beyond, but the rift valley escarpment is less pronounced on the eastern shore.
Mweru is shallow in the south and deeper in the north, with two depressions in the north-eastern section with maximum depths of 20 m and 27 m.
A smaller very marshy lake called Mweru Wantipa (also known as the Mweru Marshes) lies about 50 km to its east, and north of the Kalungwishi. It is mostly endorheic and actually takes water from the Kalungwishi through a dambo most of the time, but in times of high flood it may overflow into the Kalungwishi and Lake Mweru.
Between 1796 and 1831 Portuguese traders/explorers Pereira, Francisco de Lacerda and others visited Kazembe from Mozambique to get treaties to use the trade route between their territories of Mozambique and Angola. The Portuguese must have known of the lake, and the visitors only had to walk to higher ground about 5 km north of Kazembe's Kanyembo capital to see the lake 10 km distant. However they were more interested in trade routes than discovery, they had approached from the south and their movements were restricted by Mwata Kazembe, and they did not provide an account of it. Explorer and missionary David Livingstone, who referred to it as 'Moero', is credited with its discovery during his travels of 1867-'8.
Livingstone witnessed the devastation and suffering caused by the slave trade in the area to the north and east of Mweru, and his accounts did help rally opposition to it. The last of the slave trading in the area was as late as the 1890s, however. Meanwhile between 1870 and 1891, skirmishes and wars between the Yeke king Msiri and neighbouring chiefs and traders unsettled the area. Few Europeans had visited Mweru since Livingstone, until Alfred Sharpe in 1890–1 and the Stairs Expedition in 1892 both passed by on their way to seek treaties with Msiri. The Stairs Expedition killed Msiri and took Katanga for the King Leopold II of Belgium. Sharpe left one of his officers to set up the first colonial outpost in the Luapula-Mweru valley, the British boma at Chiengi in 1891.
The western shore of Luapula-Mweru became part of the Belgian Congo and the eastern shore part of Northern Rhodesia, a British protectorate. Although Kilwa Island is closer to the western shore, it was allocated to Northern Rhodesia, and consequently Zambia has 58% of the lake waters, and DR Congo 42%.
The first Belgian outposts on the lake were set up at Lukonzolwa and Pweto which were at various times the headquarters of their administration of Katanga. They stamped out the slave trade going north-east around the lake. The first mission station on the lake was established in 1892 by Scottish missionary Dan Crawford of the Plymouth Brethren at Luanza on the Belgian side of the lake.
The British moved their boma from Chiengi to the Kalungwishi, with one or two British officers (such as Blair Watson), and a force of African police. In conjunction with operations around Abercorn further down the trade route, this was enough to end the slave trade going east from Mweru, but not enough to bring Mwata Kazembe under British rule, and a military expedition had to be sent in 1899 from British Central Africa (Nyasaland) to do that job (see the article on Alfred Sharpe for more details).
The move of the boma from Chiengi to Kalungwishi had the effect of leaving the Belgian boma at Pweto a free rein at the northern end of the lake, leading a hundred years later to about 33 km² of Zambian territory next to Pweto being ceded to the DR Congo (then Zaire). See the Luapula Province border dispute for further details and references.
After 1900, the Belgian Congo province of Katanga on the western shores of the lake developed faster than the Northern Rhodesian side, the Luapula Province and the town of Kasenga a few hours by boat up the Luapula River became the most developed in the Luapula-Mweru valley, and until the 1960s was the main commercial centre with better services and infrastructure than elsewhere. The Elizabethville mines started up more quickly than those of the Copperbelt, and Kasenga supplied its workforce with fish. Since 1960, political crises, government neglect and wars on the Congolese side have produced a deterioration in infrastructure, while peace on the Zambian side has produced an increase in population and services, causing the balance to change .
Besides Kilwa Island, there are two other inhabited islands in the lake: Zambia's Isokwe Island of 3 km², and a 2 km² Congolese island next to the mouth of the Luapula. (Two other islands in the Luapula swamps have shores on the lake).
The Congolese side of the lake was affected by the Second Congo War of 1999-2003, from which it is still recovering. Many refugees entered Zambia at Pweto and were accommodated in camps in Mporokoso and Kawambwa districts.
The Mweru area was served only by dirt roads until the main Luapula Province road on the Zambian side was tarred to Nchelenge in 1987; the population around the lake has grown, much of it exploiting the rich fishery of the lake. When the Copperbelt mines shed workers in the 1980s and 1990s, many ex-miners relocated to the lake shores particularly around Nchelenge-Kashikishi.
The dirt roads on the Congolese side have been neglected and are in poor condition, and many people cross into Zambia to travel by road. See Congo Pedicle road for more details.
Commercial fishing on Lake Mweru and the Luapula River was pioneered by Greek fishermen from the Dodecanese islands who settled in Kasenga, DR Congo, on the western bank of the Luapula 150 km up river from the lake in the first half of the 19th Century. They used boats built in Greek style powered by charcoal-fuelled steam engines, later replaced with diesel. They supplied the workforce of the copper mines in Lubumbashi (later the whole Copperbelt) with fish which was packed in ice at Kasenga and transported from there in trucks. It was estimated in 1950 there were 50 Greek boats catching 4000 t of fresh fish per year. It would take a week for a boat to do the round trip to the lake and fill its hold, lined with ice carried on board.
In recent decades the catch has declined due to over-fishing, and is estimated at 13,000 tonnes caught from 4,500 small craft, mainly plank boats. Congolese fishermen catch the most despite have the slightly smaller share of the waters. The Tilapia are caught by gill nets, and do not reach the size they once did. Since the 1980s, 'chisense' fishing increased. This method is used to catch small pelagic fish called kapenta, originally from beaches but now using lights on boats at night to attract the fish which are then scooped up in fine nets.