Birim River
Encyclopedia
Pra River (Ghana)
The Pra River is a river in Ghana, the easternmost and the largest of the three principal rivers that drain the area south of the Volta divide. Rising in the Kwahu Plateau near Mpraeso and flowing southward for 240 km through rich cocoa and farming areas and valuable forests in the Akan...
in Ghana
Ghana
Ghana , officially the Republic of Ghana, is a country located in West Africa. It is bordered by Côte d'Ivoire to the west, Burkina Faso to the north, Togo to the east, and the Gulf of Guinea to the south...
and the country's most important diamond
Diamond
In mineralogy, diamond is an allotrope of carbon, where the carbon atoms are arranged in a variation of the face-centered cubic crystal structure called a diamond lattice. Diamond is less stable than graphite, but the conversion rate from diamond to graphite is negligible at ambient conditions...
-producing area, flowing through most of the width of the Eastern region
Eastern Region (Ghana)
The Eastern Region is one of Ghana's ten administrative regions. It covers an area of 19,323 square kilometres, which is about 8.1% of Ghana's total land area. The region is divided into administrative districts. The total number of districts were increased from 17 districts to 21...
. The river rises in the east of the Atewa Range
Atewa Range
The Atewa Range is in the Akyem Abuakwa region of southeastern Ghana, near the town of Kibi, and south-west of the Kwahu Plateau which forms the south-west boundary of Lake Volta. The range runs roughly north-south, consisting of steep-sided hills with fairly flat summits...
, flows north through the gap between this range and the Kwahu Plateau
Kwahu Plateau
The Kwahu Plateau is a long plateau in Ghana. It forms the country's watershed, separating the two main river networks in the country....
, then runs roughly south-west until it joins the Pra. It gives its name to the Birimian
Birimian
The Birimian rocks are major sources of gold and diamonds that extend through Ghana, the Ivory Coast, Guinea, Mali and Burkina Faso. They are named after the Birim River, one of the main tributaries of the Pra River in Ghana and the country's most important diamond-producing area...
rock formation, which yields most of the gold
Gold
Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...
in the region. Ghana is the second largest producer of gold in Africa
Africa
Africa is the world's second largest and second most populous continent, after Asia. At about 30.2 million km² including adjacent islands, it covers 6% of the Earth's total surface area and 20.4% of the total land area...
.
Geology
The Birim River basin lies in the Man ShieldMan Shield
The Man Shield or Leo-Man shield or craton is a geological area in the southeast of the West African craton, in part overlaid by gold-bearing Birimian formations....
area of the West African craton
West African craton
The West African craton is one of the five large masses, or cratons, of the Precambrian basement rock of Africa that make up the African Plate, the others being the Kalahari craton, Congo craton, Saharan Metacraton and Tanzania craton. These land masses came together in the late Precambrian and...
, which has been overlaid by Early Proterozoic
Proterozoic
The Proterozoic is a geological eon representing a period before the first abundant complex life on Earth. The name Proterozoic comes from the Greek "earlier life"...
metasedimentary Birimian
Birimian
The Birimian rocks are major sources of gold and diamonds that extend through Ghana, the Ivory Coast, Guinea, Mali and Burkina Faso. They are named after the Birim River, one of the main tributaries of the Pra River in Ghana and the country's most important diamond-producing area...
rocks. These rocks appear to have originated in mid-oceanic arcs of volcanoes, which formed a crust that collided with and rode over the Man shield portion of the West African Craton and was compressed to form a series of folds generally trending northeasterly. The Birimian rocks include Akwatian formations, named after the town of Akwatia
Akwatia
Akwatia is a town in the Eastern region of Ghana west of the Atewa Range in the Birim River basin with a population of about 23,000. It is the main center of diamond extraction in the country.-Administration:...
in the Birim valley, which have yielded more than 100000000 carats (20,000 kg) of diamonds. The great majority of the diamonds are found in Harzburgitic
Harzburgite
The ultramafic igneous rock, harzburgite, is a variety of peridotite consisting mostly of the two minerals, olivine and low-calcium pyroxene ; it is named for occurrences in the Harz Mountains of Germany. It commonly contains a few percent chromium-rich spinel as an accessory mineral...
rocks and seem to have crystallized at unusually high temperatures and pressures deep in the lithosphere
Lithosphere
The lithosphere is the rigid outermost shell of a rocky planet. On Earth, it comprises the crust and the portion of the upper mantle that behaves elastically on time scales of thousands of years or greater.- Earth's lithosphere :...
.
Environment
The river rises in the KibiKibi, Ghana
Kibi or Kyebi is a town in southeastern Ghana on the eastern slopes of the Atewa Range, and is the capital of the East Akim Municipal District. It lies at an altitude of 318 m, and has a population of about 23,000...
or Akim district of the Eastern Region
Eastern Region (Ghana)
The Eastern Region is one of Ghana's ten administrative regions. It covers an area of 19,323 square kilometres, which is about 8.1% of Ghana's total land area. The region is divided into administrative districts. The total number of districts were increased from 17 districts to 21...
of Ghana, in the Atewa Range
Atewa Range
The Atewa Range is in the Akyem Abuakwa region of southeastern Ghana, near the town of Kibi, and south-west of the Kwahu Plateau which forms the south-west boundary of Lake Volta. The range runs roughly north-south, consisting of steep-sided hills with fairly flat summits...
, which rises to 780m. The surrounding lowlands are about 180-200m above sea level. Much of the Atewa range is a forest reserve, with large areas of primary forest holding many rare plant, animal and insect species despite persistent timber poaching. There are many unstudied archeological sites. The Kibi area has 1500–2000mm of rain annually.
The Birim basin is in the wet semi-equatorial zone of Ghana. There are two rainy seasons, one from May to June and the second from September to October. In the drier seasons, temperatures are around 26oC in August and 30oC in March. Relative humidity is 70% - 80% throughout the year. At one time covered by dense tropical forest, large areas have been cleared for farming. Ghana's forest area dropped from 8.2 million hectares around 1900 to 1.6 million hectares by 2000, and continues to decline due to demand for exports and for construction material by the growing population. Managed plantations are being introduced and may help to reverse the decline.
The river water contains levels of faecal coliforms and streptococci, mostly of human origin but in some cases due to pollution from livestock operations, that make it unsafe to drink without treatment. Below Akwatia the river holds high levels of silt from the mining operations.
Mineral Wealth
The Birim basin is rich in minerals and has been a source of gold for centuries, the basis for the former name of Ghana: the Gold CoastGold Coast (region)
The Gold Coast was the region of West Africa which is now the nation of Ghana. Early uses of the term refer literally to the coast and not the interior. It was not until the 19th century that the term came to refer to areas that are far from the coast...
. It is also a major source of diamonds.
Gold
Placer mining
Placer mining is the mining of alluvial deposits for minerals. This may be done by open-pit or by various surface excavating equipment or tunneling equipment....
, used in making ornaments and for trans-Saharan trade long before the Europeans discovered the Gold Coast. Starting in the late 19th century, British
British people
The British are citizens of the United Kingdom, of the Isle of Man, any of the Channel Islands, or of any of the British overseas territories, and their descendants...
gold mining companies adopted conventional mining and extraction processes, developing deep underground mines in the underlying Ashanti belt. After independence in 1957 the government nationalized the gold mining industry. With inadequate investment, the mines deteriorated and profitability fell. However, after privatization in 1992 the new owners injected capital, mostly into the Ashanti belt mines, discovering new world-class deposits. The Ashanti Belt now has an aggregated gold endowment of over 125,000,000 ounces of gold.
Diamonds
Ghana has produced gems from alluvial gravels since the 1920s, mostly industrial grade. In the early 1990s the government announced plans to privatize its diamond-mining operations but found no buyers. The government still owns Ghana Consolidated Diamonds, since 2005 the only formal commercial producer of diamonds. Ghana Consolidated Diamonds uses a strip and mine method at their placer mine in Akwatia, using ManitowocThe Manitowoc Company
Manitowoc Company Inc is a global company specializing in products for the food service and construction industries. Manitowoc recently completed the divestiture of their marine division in January 2009.-History:...
draglines. The plant is old and obsolescent, available only 38% of the time and producing under capacity. The government is looking for a strategic investor to take over the mine.
In 1989 the government of Ghana set up the Precious Minerals Marketing Corporation (PMMC) to promote small-scale gold and diamond mining and to purchase and resell the output. As much as 70% of the diamonds were smuggled out of the country before the PMMC was created. In its first sixteen months of operation, the PMMC bought 382423 carats (76.5 kg) of diamonds and 20,365 ounces of gold and sold 230000 carats (46 kg) of diamonds worth US$8 million. However, because of complaints over raw gem sales, the government in March 1992 ordered an investigation into the operations of the state agency and suspended its managing director.
In the 1950s and 1960s the Akwatia area of the Birim valley produced more than 2000000 carats (400 kg) annually. However, both volumes and quality are declining. Ghana produced a total of about 800000 carats (160 kg) of diamonds in 1995, about half of it from Akwatia. The available reserves cover an area of 240 km2 along the Birim River and are estimated to contain 14000000 carats (2,800 kg) of proven reserve. Although the Akwatia deposits are nearly depleted, large additional resources have been identified in the nearby Birim River deposits, including an altered meta-lamproite
Lamproite
Lamproites are ultrapotassic mantle-derived volcanic and subvolcanic rocks. They have low CaO, Al2O3, Na2O, high K2O/Al2O3, a relatively high MgO content and extreme enrichment in incompatible elements....
that may represent a primary diamond source.
Most of the diamond production in the Birim basin is now by artisanal miners from alluvial and in situ diamond deposits near Akwatia. There is some evidence that production volumes from these small-scale operations are increasing.
Bauxite
The Atewa RangeAtewa Range
The Atewa Range is in the Akyem Abuakwa region of southeastern Ghana, near the town of Kibi, and south-west of the Kwahu Plateau which forms the south-west boundary of Lake Volta. The range runs roughly north-south, consisting of steep-sided hills with fairly flat summits...
at the headwaters of the river contains extensive bauxite
Bauxite
Bauxite is an aluminium ore and is the main source of aluminium. This form of rock consists mostly of the minerals gibbsite Al3, boehmite γ-AlO, and diaspore α-AlO, in a mixture with the two iron oxides goethite and hematite, the clay mineral kaolinite, and small amounts of anatase TiO2...
deposits with minor kaolin occurrences, which are being evaluated by groups such as BHP Billiton
BHP Billiton
BHP Billiton is a global mining, oil and gas company headquartered in Melbourne, Australia and with a major management office in London, United Kingdom...
. However, the bauxite deposits are generally poor quality compared to larger deposits of higher-quality bauxite in nearby Guinea
Guinea
Guinea , officially the Republic of Guinea , is a country in West Africa. Formerly known as French Guinea , it is today sometimes called Guinea-Conakry to distinguish it from its neighbour Guinea-Bissau. Guinea is divided into eight administrative regions and subdivided into thirty-three prefectures...
and are in an environmentally sensitive area, so are unlikely to be developed.
Farming
Cassava
Cassava , also called yuca or manioc, a woody shrub of the Euphorbiaceae native to South America, is extensively cultivated as an annual crop in tropical and subtropical regions for its edible starchy tuberous root, a major source of carbohydrates...
, yam
Yam (vegetable)
Yam is the common name for some species in the genus Dioscorea . These are perennial herbaceous vines cultivated for the consumption of their starchy tubers in Africa, Asia, Latin America and Oceania...
, cocoyam
Cocoyam
Cocoyam can mean:* Taro - old cocoyam* Malanga - new cocoyam...
, maize
Maize
Maize known in many English-speaking countries as corn or mielie/mealie, is a grain domesticated by indigenous peoples in Mesoamerica in prehistoric times. The leafy stalk produces ears which contain seeds called kernels. Though technically a grain, maize kernels are used in cooking as a vegetable...
, rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...
and vegetables, and commercially more valuable crops such as citrus
Citrus
Citrus is a common term and genus of flowering plants in the rue family, Rutaceae. Citrus is believed to have originated in the part of Southeast Asia bordered by Northeastern India, Myanmar and the Yunnan province of China...
, pineapple
Pineapple
Pineapple is the common name for a tropical plant and its edible fruit, which is actually a multiple fruit consisting of coalesced berries. It was given the name pineapple due to its resemblance to a pine cone. The pineapple is by far the most economically important plant in the Bromeliaceae...
, pawpaw
Papaya
The papaya , papaw, or pawpaw is the fruit of the plant Carica papaya, the sole species in the genus Carica of the plant family Caricaceae...
and cola nut. The region also produces exotic crops such as black and sweet pepper, ginger
Ginger
Ginger is the rhizome of the plant Zingiber officinale, consumed as a delicacy, medicine, or spice. It lends its name to its genus and family . Other notable members of this plant family are turmeric, cardamom, and galangal....
, cashew nuts, rubber
Rubber
Natural rubber, also called India rubber or caoutchouc, is an elastomer that was originally derived from latex, a milky colloid produced by some plants. The plants would be ‘tapped’, that is, an incision made into the bark of the tree and the sticky, milk colored latex sap collected and refined...
and mangoes, which are gaining importance as export commodities. Cocoa farming is one of the more important sources of income, with the dried product exported for further processing. Palm oil
Palm oil
Palm oil, coconut oil and palm kernel oil are edible plant oils derived from the fruits of palm trees. Palm oil is extracted from the pulp of the fruit of the oil palm Elaeis guineensis; palm kernel oil is derived from the kernel of the oil palm and coconut oil is derived from the kernel of the...
production is also increasing, with byproducts used for making soap locally. Bamboo
Bamboo
Bamboo is a group of perennial evergreens in the true grass family Poaceae, subfamily Bambusoideae, tribe Bambuseae. Giant bamboos are the largest members of the grass family....
is another important crop. The fast-growing plant provides inexpensive material for construction and in furniture making.
Tourism
The government is attempting to develop the tourist potential of the region. The Atewa Range forest reserve is managed by the Okyeman Environment Foundation, which has restricted people from farming in the area and instead is trying to encourage eco-tourism.The Birim South District has attractive scenery, waterfalls, historic places and nine forest reserves. The Ghana Tourist Development Board, in collaboration with the District Assembly and Traditional Authorities has developed a Business Plan for developing the "Big Tree" site in the Esen Epan Forest Reserve near Akim Oda
Akim Oda
Akim Oda or Akyem Oda is a town in the Eastern Region of Ghana with a population of about 38,000 people. It is the capital of the Birim Central Municipal district...
as a tourist site, in cooperation with the private sector. This site has the biggest tree in West Africa
West Africa
West Africa or Western Africa is the westernmost region of the African continent. Geopolitically, the UN definition of Western Africa includes the following 16 countries and an area of approximately 5 million square km:-Flags of West Africa:...
at 12 meters in circumference and 66.5 meters tall. Working with the University of Georgia
University of Georgia
The University of Georgia is a public research university located in Athens, Georgia, United States. Founded in 1785, it is the oldest and largest of the state's institutions of higher learning and is one of multiple schools to claim the title of the oldest public university in the United States...
, plans are being made to improve the access roads, eating and relaxation places, souvenirs and shops.
In the town of Akyem (Akim) Oda
Akim Oda
Akim Oda or Akyem Oda is a town in the Eastern Region of Ghana with a population of about 38,000 people. It is the capital of the Birim Central Municipal district...
, the capital of the Birim South District
Birim South District
The Birim South District is a district of Ghana in the Eastern Region. The Birim River flows through this district. It was created in 2008 after the Kufuor government created more administrative districts...
, attractions include dug-out boat tours to view the mining operations, traditional ceremonies usually including impressive drumming performances and a bustling outdoor market. The exotic and tasty local food may also be an important attraction.