Stanley Pool

The Congo River is divided into the lower and the upper river. The first part is only 115 miles long, and extends to Matadi. Here it is fifty fathoms deep, and in one spot, just above, ninety, and this section was consequently navigable for ocean steamers of considerable size. A little beyond Matadi there begins a series of cataracts and furious rapids, some thirty in number, and other impediments, which continue to Stanley Pool, a distance of 220 miles. From Stanley Pool there is a clear and uninterrupted course of 1,000 miles. From Leopoldville to Stanleyville, at the foot of the Stanley Falls, a distance of nine hundred and eighty miles, navigation is uninterrupted all the year round.

As the new wave of missionaries and explorers sought to penetrate the African heartland by ascending the Congo River, it became apparent that a reliable line of communications had to be built across Bas Zaire in order to by-pass the 300 miles of rapids on the lower river and connect the boast with Kinshasa, the port-of-entry to the great navigable stretches of the Congo River and its drainage basin.

The river has not always looked the way it does today. Some geologists estimate that perhaps as recently as half a million years ago, the Congo was a large lake, or series of lakes, with no outflow to the Atlantic Ocean. At some point, the Congo breached a high plateau in the region of present-day Pool Malebo--a peculiar place where the river expands into an enormous 14 mile- (22.5 kilometer-) wide pool. In Conrad's day, this strange place was known as Stanley Pool, after Henry Morton Stanley, the explorer and emissary of the now infamous Belgian King Leopold II.

Most of the great inland lake was drained and a "new" river cascaded down through the gorges of the Crystal Mountain region, dropping about 920 feet (280 meters) over 220 miles (350 kilometers) to reach the Atlantic. Today, some of the most spectacular rapids on Earth and a rich endemic fish fauna are found in the river as it flows between Pool Malebo and the Atlantic.

Malebo Pool – formerly Stanley Pool, also known as Lake Nkunda - is directly above Kinshasa. Brazzaville and Kinshasa are situated on its NW and SW shore, respectively. The Republic of the Congo, originally a French colony, is sometimes called Congo-Brazzaville—as opposed to the Democratic Republic of the Congo (known from 1971 to 1999 as Zaire) which is often called Congo-Kinshasa, originally a Belgian colony. Brazzaville has a population of 600,000, compared with Kinshasa’s 6.8 million.

Malebo Pool is located between Douvre cliffs upstream and the Kintambo rapids downstream. It is about 35 km long and 25 km wide and seldom exceeds 10 m in depth. Water levels fluctuate by about 3 m within the year. Water moves quickly through the pool as it makes its way towards the ensuing rapids.

The Pool Malebo is about 35 km long, 23 km wide and 500 km2 in surface area. Its central part is occupied by M'Bamou or Bamu Island (180 km2), which is Republic of the Congo territory. The pool is shallow with depths of 3–10 meters, while water levels vary by as much as 3 meters over the course of a year at an average elevation of 272 meters (900 ft).

At the eastern end of Stanley Pool, where the river leaves the narrow channel and begins to expand, the greatest depth is close up against the precipitous northern bank. Ascending the Congo from Stanley Pool eastwards, the course of the river for a hundred and twenty-five miles is confined between steep-faced hills on either side. Between left and right bank the distance ranges from one to two miles, generally less than one mile. The hills rise to eight or nine hundred feet above the river for some distance from the Pool; but about a hundred miles east of this expansion these wooded cliffs are seldom much more than half that height, are much less steep, and begin to recede from the water's edge. At a point eighty-five miles east of Stanley Pool the Kasai joins the Congo, pouring its immense volume into it at a right angle through a deeply cut chasm in the rocky hills some seven hundred yards in width.