Boundaries

The Upper Lualaba ecoregion is defined by the Kamolondo Depression, and additionally by the wetlands, swamps, and lakes along the Lualaba River below the depression and along the adjacent Lululwe, Kilubi, and Lovoi Rivers to the west. The ecoregion lies within the Democratic Republic of Congo in the southeastern portion of its Shaba Province. 

Topography

The Kamolondo Depression covers an area 100 km wide and 400 km long between the Hakansson Mountains to the west (up to 1,200 m asl) and the Manika Plateau and Mulumbe Mountains to the east (up to 1,889 m asl) (Bailey 1986). The depression itself is at an elevation of about 1,000 m asl at its southwestern end, declining steeply to about 600 m asl and flattening out to form a series of lakes (Hughes & Hughes 1992). The well-mixed lakes and marshes of Upper Lualaba begin in this flatter portion of the depression, where elevations stay at about 500 to 600 m asl and extend for a total of 225 km.

Geologically, the Kamolondo Depression is a graben, a valley formed by an extension of the earth’s crust, probably during the Miocene-Pliocene (Poll & Renson 1948; Hughes & Hughes 1992). It is likely that an ancient lake once covered the depression (Bailey 1986). Sedimentation from the Lualaba, Luvua, Lufira, and Luvoi Rivers would have infilled the lake to form the swampy region present today (Denny 1985).     

Freshwater habitats

The waters of the upper Lualaba River, teeming with life, flow through the swampy valley of the Kamolondo Depression. Within this depression, a continuous swamp belt fringes the river and a series of lakes are connected to the river through narrow channels.  

Lake Upemba, with an area ranging between 500-800 km² and a 70 km-long basin, is the largest of the lakes (Bailey 1986). Like the other lakes, it is shallow; with maximum depth reported to be only 3.2 m (Hughes & Hughes 1992). The lake is regularly stirred by winds and becomes supersaturated with oxygen at its bottom during the day. It is highly eutrophic and the site of intense algal production (Beadle 1981). The northern half of the lake is covered almost entirely with plants like Typha domingensis (Hughes & Hughes 1992).

The Lualaba River winds through the lake region and is joined below Lake Upemba by its largest tributary, the Lufira River. The Lufira derives much of its flow from calcareous subterranean streams and affluents that themselves receive input from warm saline springs. As the Lualaba leaves the depression, it is about 100 m wide (Bailey 1986). It then travels through a swampy belt that extends for 80 km and contains a cluster of small lakes, including Lakes Kittongola and Towe (Hughes & Hughes 1992).

 

The Lualaba and Lufira flood seasonally in response to the rains. Water level in the Lualaba is highest from February to April and lowest from August to October, with a total fluctuation of 2.8 m in the southern section of the ecoregion. Lake water levels also fluctuate; Lake Upemba is high from March to June and low from October to January (Hughes & Hughes 1992). 

Tall herbaceous vegetation dominates the swamps along the rivers and the lakes, with Cyperus papyrus and Typha domingensis prevalent. The papyrus swamps of this ecoregion are extensive. During the dry season the Lualaba flows through a navigable (usually dredged) channel, but in the wet season the areas surrounding the river become inundated and floating mats of papyrus can obstruct the channel (Bailey 1986). Common floating aquatic vegetation includes Nile lettuce (Pistia stratiotes), water chestnut (Trapa natans), Nymphaea caerulea, N. lotus, and Nymphoides indica (Marlier 1973). Pycreus mundtii and Paspalidium geminatum commonly grow on the swamp edges (Hughes & Hughes 1992). Swamp woodland patches occur on elevated sandy sites and are dominated by ambatch (Aeschynomene elaphroxylon) and Hibiscus diversifolius (Hughes & Hughes 1992). These sites are often inundated from 40 to 60 cm. 

Terrestrial habitats

In the south of the ecoregion the vegetation cover is primarily savanna, and changes to taller and denser forest to the north (Hughes & Hughes 1992). Grasslands dominate the plateau and Uapaca, Brachystegia, and Isoberlinia woodlands occur on lands adjacent to the wetlands (Demey & Louette 2001).

Description of endemic fishes

The Lualaba/Upemba and the Lufira systems have distinct fish communities, each with at least 14 endemic fish taxa. Rapids tend to contain specialized species, and the rapids of the Lufira River are known to host several endemic fishes including cichlids (e.g. Lamprologus symoensi), kneriids (e.g. Kneria katangae), and mochokids (e.g. Chiloglanis lufirae).

Other noteworthy fishes

Cichlids are numerous in the lakes and rivers of the Upemba area, and Oreochromis upembae, which is found in only three ecoregions, is an abundant species (Banister 1986).

Justification for delineation

It is likely that an ancient lake once covered the depression (Bailey 1986). Sedimentation from the Lualaba, Luvua, Lufira, and Luvoi Rivers would have infilled the lake to form the swampy region present today (Denny 1985) that is characterized by freshwater species adapted to swamps and open water.     

Level of taxonomic exploration

Poor. Recent surveys have not been conducted in this ecoregion and little historic data on fish and aquatic invertebrates exist.