Reverse Osmosis & Water Treatment in Gambia
The Gambia, officially the Republic of the Gambia, is a country in West Africa. It is surrounded by Senegal, apart from a short strip of Atlantic coastline at its western end. It is the smallest country on mainland Africa. The country is situated either side of the Gambia River, the nation's namesake, which flows through the country's centre and empties into the Atlantic Ocean.
It is the smallest country on the African continent with a total area of 11,300 square kilometers (km2), of which about 20% is considered as wetland. The River Gambia runs from east to west, dividing the country in two strips of land 25 to 50 kilometers (km) wide and about 300 km long.
In the Gambian landscape two major geomorphological units may be distinguished, the uplands and the lowlands:
•On the upland plateaus, weathered tropical soils are found. These soils have low intrinsic fertility and low water retention capacity, but their drainage conditions are good. The plateau is intersected by watercourses flowing downwards on the lowlands. These streams have formed narrow fluvio-colluvial valleys (Wulumbangos).
•The lowlands include the floodplain of the River Gambia in the Upper Valley (UV), and tidal plains (Bantafaros) in the Central Valley (CV) and Lower Valley (LV). The soils of the lowlands are flat, fine textured, and poorly drained. In the LV potentially acid sulphate soils occur, which can become acid sulphate soils unless waterlogging is prevented by drainage.
The vegetation of the Gambia is of the savanna type with shrub and grass understories. Mangroves are found in the western half of the country in the floodplains of the River Gambia. The cultivable land area is estimated at about 430,000 hectares (ha), which is 38% of the total area. In 2002, arable land was 250,000 ha, while 5,000 ha were under permanent crops (Table 1).
The Gambia lies in the Sahelian agro-climatic zone and its climate is characterized by two different seasons: a rainy season from June/July to October and a long dry period between November and May. The dry season is characterized by a hot, dry wind blowing southwards from the Sahara desert, which can bring sandstorms. There has been a steady decline in rainfall from 1875 onwards which is causing increased salinity in the lowlands and increased aridity in the uplands. Average annual rainfall is 836 millimeters (mm), with a spatial variation from over 1,000 mm in the south to less than 800 mm in the north. In the areas where there is less rainfall, it is generally more reliable. As much of the wet season rainfall falls in short heavy storms, water conservation is essential to ensure crop security. However, there is a risk of washout due to the severity of the rainfall. The average daily temperature is 30°C in the dry season and 27°C in the wet season.
The River Gambia originates in Fouta Djallon in the mountain region of Western Guinea and flows through Senegal before entering the Gambia. Within the country, the River Gambia flows from east to west for about 400 km. It is a major waterway and tourist attraction. Its floodplains, riverbanks, and wetlands are important habitats for wildlife and play an important role in local livelihood strategies. Its flow is highly seasonal. The maximum flow occurs at the end of the rainy season in late September or October with a flow of about 1,500 m3/s; the minimum dry season flow is less than 4.5 m3/s. Both measurements are taken at Gouloumbo in Senegal. Because of the flat topography there is a pronounced marine influence and the river’s seasonality and salinity have important repercussions on land use.
The country’s total actual renewable water resources are estimated at 8 km3/year, of which about 3 km3 are internally produced and the remaining 5 km3 represent the inflow of the River Gambia from Senegal (Table 2). It is estimated that internally produced groundwater amounts to about 0.5 km3/year, all of which is drained by the River Gambia and becomes the base flow of the river. Groundwater is available in all parts of the Gambia. The country is located in one of Africa’s major sedimentary basins and is often referred to as the Mauritania/Senegal Basin. It is characterized by two main aquifer systems with water table depths varying from 10 m to 450 m.
Along the river, the width of the valley varies from 20 to 40 km and three major sections may be distinguished:
•The Upper Valley (UV), where floods occur occasionally and water is always fresh.
•The Central Valley (CV), where tidal influence exists but water is also fresh. In the lower CV water is fresh only during the rainy season while in the dry season, when the salt tongue moves as far as 250 km upstream, it becomes brackish. Thus, in the dry season, about 220 km of freshwater are left in the Central and Upper River Divisions.
•The Lower Valley (LV), where water is perennially saline because of permanent tidal influence.
Total water withdrawal was 31.8 million m3 in 2000. The largest water user was agriculture with 21.3 million m3/year (67%), followed by the domestic sector with 6.9 million m3/year (22%) and industry with 3.6 million m3/year (11%) (Table 2 and Figure 1).
Surface water is rarely used as a source of potable water in the Gambia, because of the continuously saline conditions which exist in the lower reaches of the River Gambia and its tributaries, where the population centers and tourism facilities are located. The potable water demand for urban areas, tourism, industry, irrigation, and livestock watering is supplied by groundwater sources.
International Water Issues
The Gambia is located entirely within the Gambia River Basin, which is shared between Senegal (77.5% of the basin area), the Gambia (13%), Guinea, (9%) and Guinea-Bissau (0.5%). The Gambia signed several international agreements and conventions regarding the Gambia River Basin, namely:
•Agreement for the integrated development of the Gambia River Basin (1968)
•Convention creating the coordinating committee of the River Gambia (1976)
•Convention relating to the status of the River Gambia (1978)
•Convention relating to the creation of the Gambia River Basin development organization (1978)
The World Bank reports that at least 80 countries have water shortages and 2 billion people lack access to clean water. More disturbingly, the World Health Organization has reported that 1 billion people lack enough water to simply meet their basic needs, unfortunately in many countries water is scarce or contaminated.
Pure Aqua provides wide range of filtration and economical solutions based on the Gambia's
Gambia's main water resources are:
Surface water “is water from river, lake or fresh water wetland, which can be treated using different methods, such as Ultrafiltration Systems, Media Water Filters, Brackish Water RO.
Desalination can be used for water from ocean, or sea source, which can be treated using Sea Water Reverse Osmosis Systems; Desalination Systems
Ground Water or brackish water is from water located in the pore space of soil and rock “Borehole well”, which can be treated using Reverse Osmosis Systems, Media Water Filters, Chemical Dosing, UV Sterilizers.
Government water supply, which could have high level of hardness or high level of chlorine, can be treated with Water Softeners, Media Water Filters
Pure Aqua manufactures water treatment systems that meet the World Health Organization requirements.
Completed Water Purification Projects for Gambia: