The Pra River, located in southern Ghana, is a significant waterway with a rich history and a complex present. Rising in the Kwahu Plateau near Mpraeso, the river flows 150 miles (240 km) southward to its entry point into the Gulf of Guinea (Atlantic Ocean) at Shama.
Map of Ghana showing the regions through which the Pra River flows.
Geographical and Hydrological Significance
The Pra River is the easternmost and the largest of the three principal rivers that drain the area south of the Volta divide. Its main tributaries include the Ofin, Anum, and Birim rivers.
The Pra has many cataracts, notably the Bosomasi Rapids at Anyinabrim, and for most of its length is not navigable even by canoe. However, in the early part of the twentieth century the Pra was used extensively to float timber to the coast for export. This trade is now carried by road and rail transportation.
The Pra flows through a rich cocoa- and food-producing area and valuable timber forests. The Birim River valley is rich in diamonds, and the northern reaches of the Pra were formerly worked for gold.
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Archaeological and Historical Insights
Archaeological and historical data provide insights into the transformations in settlement organization and settlement patterns along the Pra River from the first millennium BC to the mid-twentieth century. Focus is on Supomu Island and Wawase, two abandoned settlement sites located in the lower reaches of the Pra River, 15 kilometers north of the coastal trading and port town of Shama.
Mapping of surface features, surface collections, shovel test pits, and test excavations are used to document intra- and inter-site artifact distributions. These lines of evidence are used in conjunction with historical sources to explore the processes of settlement formation, expansion, and abandonment at Supomu and Wawase over the past three millennia. The study illustrates how local and the emerging global processes of the Atlantic world played out within the settlement histories of these communities.
The assemblage of European trade materials including ceramics, pipes, glass beads, and liquor bottles, and local materials like pottery, stone beads, and lithics from the sites are analyzed and compared. Although limited, this study provides the first local ceramic chronology of this locality. Archaeological evidence of a lithic component that underlies the Atlantic era at Wawase suggests a long-term continuous sequence of occupation at the site. This evidence is supported by a series of radiocarbon dates, which place the earliest occupation levels at Wawase in the first millennium BC.
By contrast, at Supomu, archaeological and documentary evidence suggest an occupation period between the seventeenth and nineteenth centuries. Supomu may have functioned as a sociopolitical and commercial center in the Shama hinterland during the Atlantic period. This is evidenced in the number and variety of European trade goods and census data in 1891, as well as transitions in the Supomu toponym and modern political organization in the Shama traditional area.
The island’s importance in the region may have derived from its strategic location in the Pra River, which made it ideal for trade particularly in contraband, possibly including a continued trade in slaves during the nineteenth century following the abolition.
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The locality’s comparative isolation again played out in Wawase, the successor town of Supomu in the second quarter of the twentieth century, which expanded along the plains on the east bank of the Pra River adjacent to Supomu.
Cultural and Spiritual Significance
Rivers were deemed powerful biological agents acting as an embodiment of deities and ancestors of the people. They thus played a vital role in the political and religious structures within the customary states. There were special individuals (a priest/priestess or okomfo in Twi- pl .akomfo) within communities believed to be chosen and possessed by river deities who acted as mediators between the people and the deities.
Larger river deities were known to be accompanied by minor ones (in the physical sense, their tributaries). The roles of akomfo were multiple, and included liaising with customary authorities in managing the day to day political, cultural, and social aspects of a state or community. In essence, they were part of the core political structure and leadership of these communities and states.
Within the Ashanti kingdom, popular folktale recounts that Onyame, the Creator, decided to send his children down to earth so that they could confer benefits and blessings upon mankind. All the sons bore the names of major rivers and lakes; River Tano, Pra, Lake Bosomtwe, River Bea, and Opo the Sea among others. Tributaries of these rivers are the grandchildren of Onyame, the Creator.
Among the Akyems in the eastern region, it is also believed that Okuru BaninI (the first chief of Akyem Tafo) emerged out of the Birim River holding a burning log of firewood and his stool, accompanied by the high priest Okomfo Asare (who was believed to be also carrying the Ohum Shrine) and his clansmen. When the time came for Okuru Banin I to die, it is believed that he dived back into the Birim River.
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The Birim River is considered the abode for the ancestors who continually bless the people of Akyem Abuakwa traditional state with long life, prosperity, and victory over their enemies. In addition, the Birim River is considered a living being with significant spiritual powers.
When rivers are given such spiritual significance, the river banks, headwaters, and the entire forest around them are considered living shrines where rituals and offerings are regularly performed, especially during sacred days and festivals.
Rivers of cultural and spiritual significance are regulated by institutionalised norms and rules. Extensive taboos have long existed around the use, access, and distribution of water. These were revered, particularly because flouting them was believed to be accompanied by disasters (e.g. flooding and drought), illness, misfortunes, and death.
In the case of the River Tano, which belongs to the Bono State, one can experience severe stomach aches and even death if the no-fishing rule is violated or if one eats a fish sourced from the river. In addition to this, the majority of rivers had sacred days (Nnabone) where no mortal was expected to be seen hanging around the banks of the river or fetching from it.
Sacred days are the days that mark the birth of deities (e.g. every Wednesday will be the sacred day of a river believed to be born on Wednesday); the deity rests, or the children of the deity appear in various forms to play. The children of the deities are believed to be so beautiful that mortals are not supposed to see them. However, it was considered either a misfortune or luck for a mortal to see the spirits during the days.
These regulations were diverse and extensive, even within the different Akan states. The most common sacred river days among the various Akan communities were Tuesdays and Thursdays. Other taboos focused on water collection. It was a taboo in some communities to obtain water from rivers with any implement containing any kind of metal. Here, it was only earthenware or calabashes that were allowed. In most communities, however, women and girls who were menstruating were prevented from accessing rivers possessed by male deities.
Help the Rivers in Ghana: A Listening Field for Change
Environmental Challenges and Water Quality
Protecting water resources to ensure their sustainable use by future generations is a critical concern faced by developing countries. One is tempted to think that most developing countries are not taking advantage of the rich wealth of information available to avoid mistakes being repeated.
The release of elements of potential toxicity from legal and illegal mining sites and nutrients from agricultural fields is compounding the problem of pollution being caused by untreated wastewater from industries to water bodies. Unfortunately, regular monitoring of rivers in Ghana is not routine as it happens in other developed countries. The absence of routine monitoring has been compounded in Ghana by illegal mining, popularly known as “galamsey” (“gather them and sell”) which has swallowed many other associated environmental problems due to the havoc it has caused to water bodies.
Different ruling governments have tried many strategies to stop “galamsey” but yielded no fruitful results. The recent intervention has been operation vanguard which was introduced about six (6) years ago to stop illegal mining and introduce planting for food and jobs to take miners out of the mining sites.
The study showed a significant deterioration in the quality of the river after the first stage of implementation of integrated water resources management (IWRM). Interventions when introduced are meant for positive changes but sometimes the opposite is observed as was the case of that study.
One thing that remains undisputed is that there are no observable changes in the quality of the water esthetically. However, these observations are not enough, they must be scientifically proven, hence this monitoring. This study is extensive and covers the upstream through the midstream to the downstream and focused on both physicochemical parameters and some selected potentially toxic elements, unlike the previous study that considered only physicochemical parameters.
In summary, in the present study, the physicochemical parameters will be assessed, and the levels and ecological toxicity of potentially toxic elements will be measured.
The study was carried out in the Pra basin with a population of 4.2 million and a growth rate of 2.2% per annum. The basin cut across the Ashanti, Central, Eastern, and Western regions of Ghana with 43 administrative districts, municipal, and metropolitan assemblies. The climate is sub-equatorial wet and has two rainy seasons with May and July as the major rainy season and September-November as the minor season.
The basin is located between Latitudes 50N and 70˚30'N, and Longitudes 20˚30'W, and 00˚30'W, in south-central Ghana. The basin is scattered with unregulated illegal mining sites, however, the eight sites which were considered for previous studies by Duncan et al., [1] will be considered for this monitoring purpose. Sampling was done from the upstream to the downstream as displayed in Figure 1.
The Pra River takes its source from the Kwahu plateau in the North and travels through 240 km to join the Gulf of Guinea in the town of Shama. A total of 40 water and soil samples each were collected from 8 sampling points, into laboratory-cleaned and rinsed 1.0 L polyethylene bottles and 0.1 L polyethylene containers respectively. Samples were collected from January to April 2022. Water samples were acidified with 0.24 M nitric acids (analytical grade) and kept in an ice chest (at 4˚C) and sent to the Water and Sanitation Laboratory at the University of Cape Coast for analysis.
The heavy metal determination was conducted using a dual atomizer and hydride generator atomic absorption spectrophotometer (model ASC-7000 No A309654, Shimadzu, Japan). All the samples were analyzed for arsenic (As), lead (Pb), manganese (Mn), and iron (Fe). All reagents used were of the analytical grade from MES Equipment, Ghana. Ultrapure metal-free deionized water was used for all analyses. All glass and plastic wares were cleaned by soaking them in warm 5% (V/V) aqueous nitric acid for 6 hours and rinsed with ultrapure deionized water. The standard for ASS calibration was prepared by diluting standard (1000 ppm) supplied by MES Equipment Limited, Ghana. All measured results for soil samples were converted from milligrams per liter to milligrams per kilogram.
Concerning the interview, the focus was on any observed changes in fish harvest, species present, fish size, and what may account for the observed changes. All 8 fishermen were interviewed with one each from the eight sites. The questions were open-ended questions to allow the fishermen to express their views on the situation at stake.
| Parameter | Description | Significance |
|---|---|---|
| pH | Relative amount of free hydrogen and hydroxyl ions in water. | Affects the chemosensory ability of fish; pH range of 5-9 is generally safe for fish. |
| Total Suspended Solids (TSS) | Diameter of suspended solids is usually less than 62 µm. | Influences water physically, chemically, and biologically; high concentrations can reduce primary production of algae and macrophytes. |
| Turbidity | Measure of the cloudiness of water. | Affected by particle size and shape of SS, phytoplankton, humic substances, and dissolved mineral substances. |
Map of Ghana showing the location of the Pra River Basin.
These parameters play a very important role in the survival of both micro and macro-organisms in an aquatic ecosystem. Any anthropogenic activities that have the potential to shift these parameters out of proportion in the environment have the potential to either destroy or cause organisms to migrate to a safe environment.
The pH recorded in the study period was within the range safe for fish in the river (Table 5). The highest pH in the study area is below that of the previous studies [1]. Even though the present pH is within the range suitable for living organisms especially fishes to grow well, the situation on the field is totally different: the interview with the fishermen reveals that they continually experience low fish harvest and the disappearance of most fish species within the basin.
According to [31] SS concentration of 200 mg・L−1 would cause a 50% reduction in the primary production of algae and macrophytes. This means that all six sites may potentially be experiencing this phenomenon resulting in the reduction in oxygen levels in the river and eventually affecting the survival of fish in such locations or environments. This could be one contributing factor to the disappearance of some fish species in the river that was revealed by fishermen during the interviews.
According to Bilottaa and Braziera [27], the particle size and shape of SS, the presence of phytoplankton, the presence of dissolved humic substances, and the presence of dissolved mineral substances have a great influence on the turbidity in water.
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