ion from springs nowadays is through two spring boxes: the protection box to protect the water against surface contamination and the collection box to provide storage and ensure that the all the water from the spring is collected. Loose stones are piled up at the back of the spring box to serve as a wall and to prevent the washing away of soil. the spring boxes are often fitted with an overflow pipe and a drain pipe. From the collection chamber water is conveyed either straight to the consumers or to the service reservoir. Most of the spring capping works done in ethiopia are for small rural towns and villages and are executed at the regional level and often by NGOs working in the area. In ethiopia, wells with depth up to 60 m are normally considered as shallow. Shallow depth wells are either hand dug or augers are employed to drill or are bored using rigs. Most hand-dug wells are lined using either stone masonry or pre-cast concrete rings and when used communally it is normally covered and equipped with hand pumps. the abay river basin master plan estimates that 70 percent of the rural community of the basin gets their water GROUNDWATER AVAILABILITY AND USE IN SUB-SAHARAN AFRICA: A Review of 15 Countries 35 from hand-dug wells fitted with hand pumps and 20 percent from boreholes with submersible pumps. In rural areas where traditional dug wells are used the main water lifting equipment is the ‘‘rope and bucket’’ system. these types of wells are not well covered and mostly exposed to pollution. In wells constructed by the government and NGOs, the hand-dug wells are properly covered and fitted with hand pumps. the walls of the wells are cased with concrete rings or masonry. For shallower wells (up to a depth of 45m), mostly afridev hand pumps are fitted. For depths up to 80 m, Indian Mark II pumps are installed. these hand pumps are selected because of their simplicity during operation and maintenance. they are usually termed as ‘‘Village Level Maintained and Operated’’ (VLMO) pumps. In most places where the groundwater table is at an average depth of 10 m, privately owned hand dug wells are found. these wells are normally open and are rarely lined and may serve as a sole source of water or a supplementary source to the household. Cost of groundwater development the cost of drilling in ethiopia is very high, owing to limited drilling companies and the high price of machinery and accessories for drilling. hence development of groundwater sector requires a huge financial investment towards appropriate machinery and building capacities to handle them. In some governmental organizations like the amhara Water Works Construction enterprise (aWWCe), the cost of drilling is higher, mainly due to the greater staff numbers and the aged machineries with high maintenance cost. Cost analysis of wells shows that the percentage share of cost based on itemized costs varies from place to place and significantly from country to country. In ethiopia all drilling equipment, including vehicles, casings, fuel, oil, lubricant spare parts, etc., are imported, with the depreciation costs accounting for 33 to 42 percent, and the material costs including fuel, oil, grease accounting for 22 to 25 percent and the labour, overhead, profit margin, and Vat accounts for 33 to 45 percent (aWWCe, 2004).typical costs of groundwater development are shown in table 3.5.

https://www.iwmi.cgiar.org/Publications/Books/PDF/groundwater_availability_and_use_in_sub-saharan_africa_a_review_of_15_countries.pdf

Groundwater availability and use in Sub-Saharan Africa: a review of 15 countries

The present work is a review on the quality characteristics of groundwater in Nigeria. The aim was to collate, synthesize and analyse hydrochemical data from available literature in order to evaluate the physical and chemical character, quality and determine the sources of ions. The review process covered four major groundwater sedimentary basins viz Benin, Benue, Niger Delta, Sokoto and the Crystalline Basement Complexes. The issue of saline groundwater in parts of Benue and Niger Delta Basins were given attention. In general, data show that on the average, TDS for the groundwater from the different basins was < 250 mg/l compared to the saline groundwater with average TDS as high as 15700 mg/l. The high salinity was attributed to dissolution of salts and seawater intrusion. Nitrate concentration on the average is high especially, for Sokoto Basin indicating anthropogenic pollution. Descriptive and multivariate statistics together with cross plots indicate that the major geologic controls on the groundwater chemistry are chloride dissolution, weathering (silicate and carbonate) and ion exchange. With respect to agricultural and irrigation purposes, the groundwater are excellent besides the water from the saline groundwater from Benue Basin and the coastal aquifers.

	 

	Key words: Groundwater, chemistry, quality, Nigeri

/pdf/groundwater-chemistry-and-quality-of-nigeria-a-status-review-4hvgsko366.pdf

Groundwater chemistry and quality of Nigeria: A status review

There are considerable groundwater and surface water resources available in Nigeria; however, much less information is available on groundwater resources than the surface water. This paper reviews the groundwater resources of Nigeria, in line with recent research across the country. The occurrence of groundwater in Nigeria is dependant primarily on the geology, and groundwater regions can be classified accordingly. The extent in any given groundwater region is defined by the limits of a group of rock types with similar hydrogeological conditions. The primary aim is to produce a synoptic overview of the hydrogeological character in each groundwater basin to guide an overall management and protection of groundwater resources in Nigeria. Groundwater management and aquifer protection must be taken seriously in Nigeria to ensure the long-term sustainable use of groundwater in future generations.

An overview of the geology and hydrogeology of Nigeria

The rapid expansion of economic activities in coastal parts of Nigeria has triggered an uncoordinated development of groundwater leading to stress on the resource. Hence a study was conducted to assess the hydrogeological characteristics of the shallow coastal aquifer of southern Akwa Ibom State, Nigeria. Emphasis was on the hydraulic characteristics, quality with respect to domestic and irrigation purposes and influence of seawater. The study result revealed that the aquifer consist of intercalations of clayey sand and sand. The aquifer is characterized by high hydraulic conductivity and transmissivity values. The groundwater flow direction is southwards with higher groundwater depletion in the dry season. Groundwater samples from hand dug wells and boreholes were evaluated based on World Health Organization standard and some indices, respectively, for drinking and irrigation uses. The groundwaters are fit for drinking and domestic uses. However, more than 70 % of the pH values are not within the allowable limits of between 6.5 and 9.2 for drinking and domestic use. Therefore, it is recommended that neutralizing filter containing calcite or ground limestone should be applied to raise the pH of the groundwater. Of the 10 parameters used to assess the water for irrigation use, only sodium adsorption ratio (SAR), magnesium hazard (MH) and magnesium ratio indicated the excellent quality of these waters. Na+-K+-HCO3
 − constitute the dominant water type. Total dissolved solids and ratios of Na+/Cl−, Mg2+/Cl−, and Ca2+/SO4
 2− and saltwater mixing index (SMI) suggest some level of seawater intrusion in the area.

/pdf/hydrogeology-and-groundwater-evaluation-of-a-shallow-coastal-a0y63u0dc0.pdf

Hydrogeology and groundwater evaluation of a shallow coastal aquifer, southern Akwa Ibom State (Nigeria)

Agbor, a town in southwestern Nigeria, is underlain by the Miocene to Recent Benin Formation. Groundwater occurrence within the formation has been investigated for its quality, from which inferences are drawn on its usability and the prevalent hydrogeochemical processes in the water systems. The results indicate a chemical attribute of low pH, low total dissolved solids (TDS) and salinity. Cationic concentrations including Na+, K+, Ca2+, Mg2+ have values ranging from 0.9 to 18.9 mg/l, 0.1 to 4.2 mg/l, 1.2 to 12.8 mg/l and 0.2 to 3.5 mg/ l respectively. Concentration values of Fe 2+ , Zn 2+ , Mn 2+ and Pb 2+ range from 0.08 to 1.92mg/l, 0.12 to 4.35 mg/l, 0.0 to 0.42 mg/l and 0.0 to 0.04 mg/l respectively. Anions including HCO3 , CO3 2, Cl , SO4 2, NO3 2, PO4 2have respective concentration values ranging from 1.0 to 10.0 mg/l, 0.1 to 0.9 mg/l, 3.2 to 24.0mg/l, 0.0 to 10.3 mg/l, 0.0 to 18.4 mg/l and 0.0 to 2.4 mg/ l. The bacteriological constituents of the water samples include Total aerobic bacteria counts (5 - 535cfu/ml) and Total coliform (10 - 70MPN/100ml). A comparison of these results with various quality guidelines, suggests that the groundwater may be suitable in its untreated state for crop irrigation, but will require pH remediation and microbial disinfection to upgrade its quality for potability and use in food processing industries. Factor analysis reveals three main hydrogeochemical activities operative within the groundwater system. Factor 1 is dominant and can be related to water-soil interaction and incorporation of leached formation water along the groundwater flow path. Factor 2 is related to pollution by biochemical related substances resulting from agricultural practices in the area. Factor 3 indicates fresh groundwater recharge. An inter-play of these processes, and base exchange reactions produced dominant chloride water types (Ca-Cl, Ca-Mg-Cl, Mg-Ca-Cl, Na-Ca-Cl and NaCl), and localized occurrences of bicarbonate types (NaHCO 3 and Na-Ca-HCO 3 .

Obot A. Umoh

Papers

Quality of groundwater in the Coastal Plain Sands aquifer of the Akwa Ibom State, Nigeria