Lake Bosomtwe

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Before the sun clears the eastern rim, a man carries a single plank of hand-hewn wood down to the water and lies down on it. The plank is called a padua, and it is not a boat. It has no hull, no seat, no nail, no oar; the fisher lies flat and prone along its length and paddles with cupped hands, his face inches from the surface, working out across the lake as the mist lifts. There is a reason there is no boat. No iron may touch this water, and a plank-and-nail canoe would carry metal onto the surface of a god. The lake he is crossing has no river running into it and no river running out of it. It sits in an almost perfect circle some eight and a half kilometers wide, held in a bowl that a meteorite punched into the West African rock more than a million years before anyone gave the antelope god his name. This is Lake Bosomtwe, and to cross it on a plank is to keep faith with both of its ages at once.

The antelope god and the closed crater

The name carries the whole of the first age in two Akan words. In Twi it is Bosomtwe — bosom, the word for a deity, an obosom, joined to ɔtwe, the antelope — and the plainest reading of the compound is “the antelope god.” The point that a visitor is likeliest to miss is grammatical before it is theological. The lake is not named after a god the way a river might be named after a founder. In the tradition kept around its shore, the lake is the god: Bosomtwe is Twe himself, an obosom whose body is the water, one of the tete abosom, the ancient nature-deities of the Akan religious world through whom the withdrawn sky-god’s power reaches the working ground. The gloss “antelope god” is the tradition’s own etymology and is best carried as such rather than as settled linguistics; but the deity it names is not folklore about the lake. He is the lake.

How Twe came to be known is told as a hunter’s story, and it is told with a date the tradition itself supplies. In the conventional reckoning the discovery falls around 1648, in the founding generations of the Asante settlements, when a hunter named Akora Bompe — of Kokofu Asaaman, one of the early towns — followed a wounded antelope through the forest with his dog. The animal reached a pool of water and vanished into it and did not surface. Two things made the vanishing a revelation rather than a loss. Bompe was hunting on Akwasidae, the great sacred day that closes each forty-two-day round of the Akan calendar and on which hunting is forbidden; and the antelope had gone into the water and not come out. He read the disappearance as a god making itself known on the god’s own day, declared the animal a water-deity, and left the pool sanctified. Like the founding stories of most Akan places, this reaches the page through oral memory rather than any contemporary record — the Akan kept no alphabetic writing before the coast — and it is marked here as tradition, the charter a place tells about itself, not as dated fact. What it fixes is the relationship: a hunter, a forbidden day, an antelope that became water, and a taboo laid down at the first encounter.

The lake’s other age is far deeper, and it is written in the rock. Long before any hunter, a stony asteroid roughly a kilometer across struck this patch of forest and, in seconds, excavated the bowl the water now fills. The impact is dated to about 1.07 million years ago, in the Pleistocene, and it drove into some of the oldest ground in West Africa — the metasediments and metavolcanic rocks of the Birimian Supergroup, formed 2.1 to 2.2 billion years before the strike. The blast threw molten and shocked rock high enough and far enough that its glassy droplets fell across a wide arc: Bosomtwe is the confirmed source crater of the Ivory Coast tektites, the field of natural glass scattered west of the crater, whose finest fraction — microtektites — settles in deep-sea sediment cores off the West African coast. The International Union of Geological Sciences, which lists the site among its global geoheritage localities, describes it as arguably the best-preserved young complex impact structure known on Earth: a pronounced rim, a central structural uplift buried beneath the sediment, and a crater almost entirely filled by its lake.

That fill is the reason the place is singular in Ghana. Lake Bosomtwe is the only natural lake in the country, lying about thirty kilometers southeast of Kumasi in the Ashanti Region. It is hydrologically closed — endorheic — with no river feeding it and no outlet draining it; its level is set by rain and evaporation alone, and it stands at roughly 150 meters above sea level. The water itself is some eight to eight and a half kilometers across, cupped inside a crater rim about ten and a half kilometers from edge to edge, and it is deep: on the order of 45 meters on average and about 81 meters at its deepest. A closed, deep, steep-walled bowl of water holds its history the way few lakes do, and that is what eventually brought the drills.

The impact crater of Lake Bosumtwi seen from orbit, an almost circular basin filled by Ghana’s only natural lake, excavated by a meteorite about 1.07 million years ago. NASA Earth Observatory images by Michala Garrison, using Landsat data from the U.S. Geological Survey. Story by Adam Voiland., via Wikimedia Commons. Public domain.

Because the crater is young, deep, and undisturbed, it became one of the most closely studied impact structures on the planet. In 2004 the International Continental Scientific Drilling Program mounted the Bosumtwi Crater Drilling Project, recovering sixteen cores from six sites out on the lake between June and October — fourteen sediment cores logging the paleoclimate written into the lakebed, and two deeper cores driven through the impactite into the crater floor itself. The published overview of the project set out what the drilling confirmed: the shocked and melted target rock, the buried central uplift, the mechanics of a complex crater caught almost intact. The lake that the Asante cross on planks is, to the geologist, a nearly ideal specimen — a million-year-old wound kept clean by its own closed water.

Twe’s water and the threshold of the dead

Twe belongs to the great family of Akan water-powers. In the myths of the river-gods he is counted among the kin of Tano, the river-god reckoned king of the abosom, in the web of lakes and rivers held to descend from the earth and the sky; but where Tano is a river that runs four hundred kilometers to the sea, Twe is a god who goes nowhere. His body is a closed lake with no current and no shore beyond the crater’s own. That containment shapes what he is understood to be. He does not travel to the people; the people, living and dead, come to him.

It is the dead who give the lake its most-repeated meaning, and it is here that the sources openly disagree in a way worth marking rather than smoothing. In the account that has traveled furthest — the one in the standard reference works and in nearly every tourist telling — the souls of the departed come to Bosomtwe to bid their farewell to Asase Yaa, the earth-goddess, before they pass on; Britannica and Wikipedia both give the leave-taking in exactly those terms, and derive from it the rule that one may fish the lake only from wooden planks. But the lake is not Asase Yaa’s; it is Twe’s, the obosom whose water this is, and the community histories kept around the shore name Twe himself as the one to whom the dead take their leave. The two namings sit side by side in the record. It would be tidy to pick one, and the tidiness would be false: an outside encyclopedic tradition has settled on the earth-goddess, while the local tradition centers the god of the water, and the honest report is that a threshold-of-the-dead belief attaches firmly to the lake while the identity of who waits on the far side of the farewell is told two ways.

The shore of Lake Bosomtwe in the Ashanti Region of Ghana, the water held in the forested wall of the impact crater. Adam Jones, via Wikimedia Commons. CC BY-SA 2.0.

What is not told two ways is the discipline the god’s sanctity imposes on the water, and it is the most distinctive thing about the place. Twe’s holiness is enacted as a body of fishing law, and the law reads, at a distance of centuries, like conservation. Its first article is the ban on iron. Nothing of metal may touch the lake, and from that single prohibition the whole material culture of the fishery follows. A plank-and-nail canoe is metal on the water, and so there are no canoes; instead the fisher uses the padua — plural mpadua — a single flat plank of wood on which he lies prone and paddles out by hand, a craft that takes real skill to balance and drive and that puts the fisherman’s own body flat against the surface of the god. The absence of a boat on Ghana’s largest lake is not a poverty. It is an observance.

The rest of the taboo-regime extends the same logic of restraint. Fishing is barred on the sacred days — Sunday everywhere, and Tuesdays or Thursdays as well in particular villages according to local custom — so that the water is left unworked on a fixed rhythm through the week. Conventional nets are forbidden, and so are hooks and snares; the fisher takes what the plank and the hand allow and no more. Anything that would violate the water’s calm is proscribed: excessive agitation of the surface, loud noise, the kind of disturbance held to trouble the spirit in the lake. Women are barred from entering the water during menstruation. Read as a modern fisheries manager might read it, this is a closed season, a gear restriction, a no-wake rule, and a set of exclusion zones, all of it enforced not by a warden but by the certainty that the lake is a person who can be offended. The study of the lake’s traditional fisheries management in the Ghana Journal of Science, Technology and Development sets the prohibitions out in just this double aspect — as devotion to Twe and, at the same time, as the working rules that long governed who could take what from the water, and when.

The spiritual center of the observance is a stone. The Abrodwum stone — a sacred stone, spoken of also as a stool — is held to be the seat of the lake’s power, and it is the focus of the rite performed when the water withholds its fish. A poor catch is read as Twe’s displeasure, and the response is sacrifice made in the presence of the Asantehene, whose custodianship of the great powers of the Asante state reaches even here; the ritual custody of Bosomtwe belongs, at its apex, to the same office that keeps the Asante nation’s sacred order. In the ceremony a cow is offered, its entrails given to the stone and the remainder cast into the water, so that the god is fed from the shore and in the lake at once. The shrine priests — the akɔmfo who serve the lakeside abosom — direct these observances, and the chiefs of the shore towns levy sacrifices of animals and drink from those who have broken the taboos, to pacify the spirit whose water was disrespected. These rites are named here at the distance of the public record; the account is of that they occur and what they are for, not of how they are performed.

The lake also does something that the tradition and the laboratory both describe, and describe very differently. From time to time its fish die in great numbers, floating up across the surface in a sudden kill. In the tradition this is Twe surfacing to distribute his fish to his people — a god emptying his stores toward the shore, read as generosity rather than catastrophe. Limnology reads the same event from below. Bosomtwe is deep, closed, and stratified, and gases and dissolved compounds build up in its cold bottom water where no current disturbs them; when the cooler rainy season drives the lake to mix and turn over, that deep water is carried up, and the chemistry it brings with it — bound nitrogen that turns to toxic ammonia in the high-pH surface layer, oxygen stripped from the shallows as the load oxidizes — kills the fish. It is a limnic phenomenon, the mild cousin of the catastrophic gas eruptions recorded at deep crater lakes elsewhere. The people gather the fish that Twe has given; the scientists measure the gas that the overturn released. Neither account cancels the other, and the same silvered fish on the same morning belongs to both.

The crater read twice

Outside interest in Lake Bosomtwe has always run in two channels that rarely met. Along one, the geologists argued for a century about how the bowl was made. Nineteenth- and twentieth-century observers proposed a volcano — a caldera, a crater of eruption — against those who read the shocked rock and the ring of debris as the signature of an impact, and the impact reading won decisively, sealed by the discovery that the Ivory Coast tektites were this crater’s own ejecta and confirmed in the rock by the 2004 drilling. Along the other channel, colonial-era ethnographers and later students of Akan religion recorded the cult of Twe: the antelope legend, the plank-fishermen, the soul-farewell, the stone and its sacrifices. For a long time the crater and the god were studied by different people who did not read each other’s journals — the same water, split between a geological curiosity and a religious observance.

Today the two readings share a single, crowded place. Lake Bosomtwe is at once a living sacred site where Twe is served and his taboos kept; a national natural landmark, invariably introduced as the only natural lake in Ghana; a geoheritage locality on the IUGS global list; and, since June 2016, the core of a UNESCO Man and the Biosphere reserve, which frames the crater and its farmed and fished catchment as a landscape to be conserved with its communities rather than against them. Around the shore some thirty villages hold a combined population on the order of seventy thousand, most of them farming and fishing; the village of Abono, on the northern shore, is the gateway where visitors arrive.

Tourism is the sharp edge of the lake’s present, and it is best reported as reception rather than adopted as the tradition’s own voice. The very things that make Bosomtwe distinctive — the fisher flat on his plank, the legend of souls taking their leave, the antelope that became a god — are the things sold to visitors, packaged as the “soul lake” and the “goddess of the lake” for a market that rarely pauses on the grammar by which the lake is not named for a god but is one. The framing travels; the taboo that produced the plank does not travel with it. And the pressures that come with the visitors, the farms, and the growth press on both the ecology and the observance that once regulated it: over-fishing as demand outruns the plank’s slow yield, agricultural runoff and siltation from the cultivated crater walls, hotel and resort building along the shore, and the periodic gas-driven fish kills, all of them straining a lake whose old law assumed a smaller and more disciplined draw on the water.

The scholarship of the last decades has increasingly read Twe’s prohibitions in exactly this light — not as superstition to be corrected but as a body of indigenous conservation knowledge now eroding under the very forces that the knowledge once held in check. The Ghana Journal fisheries study and the community histories gathered by Friends of the Earth Ghana treat the no-iron rule, the closed sacred days, the ban on nets and hooks, and the exclusion of disturbance as a working management regime, centuries older than any ministry, that limited effort and gear and gave the fish their fallow. Its weakening is legible in the catch. As the sanctions lose their grip and the plank gives way in practice to faster and heavier methods, the fishery that the taboos protected declines, and the argument that Twe’s law was ecological wisdom in sacred form gains its most persuasive evidence from what happens when the law is not kept.

At dawn the mist still lifts off the water, and a man still carries his plank down to it and lies flat and paddles out by hand across a god who has no shore but the crater’s. What presses on the lake now is not doubt but weight — more villages, more nets, more visitors than the old prohibitions were shaped to hold — and a deep closed water that turns over on its own schedule and gives up its fish for reasons the priests read as a gift and the limnologists read as gas. The plank asks only that no iron touch the water. The century now leaning on the lake asks a great deal more.

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