International Association of Advances in Research and Development International Journal of Basic And Applied Sciences

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1 eissn x International Association of Advances in Research and Development International Journal of Basic And Applied Sciences International Journal of Basic and Applied Sciences, 2015, 1(2),28-34 Research Article Groundwater Quality Assessment of Different Wells in East Wollega Zone - Western Ethiopia Shayaq Ali 1 *, Muleta Ebissa 1, Diriba A.Gurmu 1, M. Vignesh Kumar 2 1 Department of Earth Sciences, Wollega University, P. O. Box 395, Nekemte, Ethiopia 2 Department of Construction Technology and Management, Wollega University, P. O. Box 395, Nekemte, Ethiopia *corresponding author, shayaqgeo@yahoo.co.in Abstract: The geochemical compositions of the groundwater of different wells in east Wollega zone bounded in 36 o 30 to 36 o 45 longitude and 9 o 00 to 9 o 15 latitude. This area was the exposure of volcanic rocks that cover the dominant parts and the quaternary sediments. Rainfall and snow melt are source of groundwater by percolating through the soil zone and unsaturated material chemically reacts with the gases, minerals and organic compounds that occur naturally within subsurface. The chemical alteration of the meteoric water depends on several factors such as interaction with solid phases, residence time of groundwater, mixing of groundwater with pockets of saline water, and anthropogenic impacts. Broadly speaking the intake of major and minor cations is related to solid water interaction. The physico- chemical characteristic of groundwater water samples have been determined according to the standard methods of APHA and identify the chemical composition of groundwater sample analysis and interpretation, like ph, EC, Cl, HCO3, Hardness, F, NO3 TDS, SO4 Ca, Mg, Na, and K which are related to solid-water interaction. This direct mixing between groundwater and outcrops are weathering and alterations of volcanic rocks and quaternary sediments. A direct relationship between lithology and relative abundances of cations is easily discernable in hard rock areas, in carbonate rock terrain Ca + Mg > Na + K, where as it is reserved in areas with arenaceous and crystalline lithology. The chemical composition of groundwater varies in the study areas, all analytical results are shown under the desirable and permissible limits of W.H.O. Standards in drinking water standard. Over one third of the total deaths in the developing countries are caused by the consumption of contaminated water. Key Words: Unsaturated material, Groundwater Sample, Quality standard, Contamination and Nekemte. 1. Introduction Background The research was conducted in East Wollega Zone which is bounded in 36 o 30 to 36 o 45 longitude and 9 o 20 to 9 o 15 latitude (Fig.1) for the identifications of groundwater quality of different wells. To overcome the objective of this research the data of geology, hydrogeological formations, physico- chemical and bacteriological water analysis, and characterize according to the given data and compared with the Ethiopian Standard and W.H.O. [1], maximum allowable concentration values. The groundwater quality of Ethiopia is both anthropogenic-ally and naturally affected. In some cases, the chemistry of groundwater is controlled by the quality of surface water due to hydraulic connection [2]. This will be true in urban centers. The main quality controls are: Geomorphological and geographical conditions, Climate, Geology (geological structures, rock composition, weathering, magmatic, geothermal activities, etc.), Biological factors (effects of micro-organisms, plants and animals), anthropogenic influences and Physico-chemical factors (temperature, pressure, chemical properties of elements, solubility of chemical compounds, ph, Eh, etc.). Based on the major cations, the groundwater can be classified as bicarbonate, sulphate and chloride types. Groundwater is precious resource for life and growth and development of country. Hence, reliance on the groundwater has increased greatly. Accordingly, substantial increments in the groundwater withdrawals have occurred in almost every part of the country. One of most fundamental condition for the growth and development of nation is certainly to fulfill its urgent water needs hence; along with this are demanded good scientific and technical capabilities for the assessment and substantial development of the country for water resource potential and considering quality particularly the groundwater. 2. Physiographic and Vegetation The weathering and fractured degree of the geology, geomorphology, tectonics and climate of the Shayaq Ali et al., Page No. 28

2 regional setup have a great role on the groundwater occurrence and quality. The variability of these factors in the area strongly influences the quantity and quality of the groundwater in different parts. The geology of the area and the surrounding provides usable groundwater and provides good transmission of rainfall to recharge aquifers, which produce springs and feed perennial rivers. According [3] the study area comprises two major physiographical landforms. These are highlands and lowlands with different plateaus and basins. The highest elevation ranges from 1500m to 3500m and the lowland part with elevation ranges from 1000m to 1500m. The total study area is highly vegetated and the type and amount of vegetation cover depends on the physiographic and climatic condition. It is mainly covered by grass, bushes, and large trees. 3. Climate and Drainage pattern The main rainy seasons in this region are from June to August during summer season and dry season during October to January. The weather is cold during the rainy season in the highland. According to the annual rainfall mapping of the study area gets annual rainfall ranging from 1500mm to 2200mm. Figure:-1 Location map of Study Area Study area is characterized by subtropical (Weina- Dega) climatic zone and c mean annual temperature. There are so many tributaries flowing from upland to low lands. They are following a dendritic pattern. Most of the streams were drained from the center of the area to the surrounding lowlands (Fig.2). Figure -2: Drainage Pattern Map of the Study Area 4. Geology of the area The area is composed of alluvium deposit (mainly composed of the clay soil) at the most top part and volcanic rocks particularly massive basalt, and weathered and fractured basalt. The clay seems developed from the insitu weathering of the underlying basalt. At many sites it has reddish to black color and variable thickness. The most abundant and dominant volcanic rock unit which composed of mostly basalt is fine grained, black to grayish in color and strongly subjected to weathering and varies degree of fracturing. The occurrence of groundwater was directly related with geological formations, geological structures, Shayaq Ali et al., Page No. 29

3 topographic variations, vegetations and climatic conditions in this report. So in this section the details of rock units and geological structures are discussed. These exposures were discussed based on their degree of weathering and fractures, colors, compositions, textures and grain size, related landforms and their typical locations, including related primary and secondary geological structures (columnar joints, faults, and fractures) with their alignments, [4] in fig Quaternary Sediments These units were exposed throughout the area as alluvial sediments and lacustrine deposits. At the west and central part of the area was dominated by weathered and fractured basalt as bedrock, the sediments from this unit is fine grained and very important for large size vegetations and multi agricultural products. In this part the sediments are dark gray color and slightly reddish at some plateaus, as they exposed from mafic weathered and fractured basalt. From the quarry site, road cut and river cut the quaternary deposits ranges from 1m 50m in thickness Weathered and Fractured Basalt This unit was covered the dominant part of the area with different degree of weathered and fractured density and distributions as discussed from drilled wells. The central, western and some other parts of the area were exposed by this unit. It is dark in color when fresh sampled and with pink yellowish weathered color. Compositionally, it is pyroxene, olivine, quartz and some fragments with different color. It is fine to medium grained and slightly distributed and interconnected vesicular textures. As it is observed and described from river cut, quarry site, hillside and drilled wells it comprises thick exposures ranging from 20m to 1000m. This unit exposed with different landforms and it causes for the existence of springs through fractures and contacts between different rock units and landforms. In this annually high rainfall causes the development of weathering and alterations which the main reasons for the existence of secondary porosity and permeability, and great influence on groundwater quality. In addition to serving as Figure -: 3: Geological Map of the Study Area aquifer this out crop is very important as raw material for road constructions [4]. The study area was deformed and characterized by different landforms which are exposed with different trends and elevations. Following the general trend of the deformation which is northwest direction locally there are various structures with different orientations and other volcanic landforms. The dominant geological structures exposed in the area are joints, fault and fractures and other volcanic structures such as; volcanic dome, columnar joints, volcanic ridge, and etc, that increases the potential of groundwater serving as conduit. 5. Hydrogeology The main features important for groundwater occurrence in crystalline rocks are weathered zones (regolith) and fractured zones. The weathered layer, also called regolith, developed on intact volcanic and sedimentary rocks is an important source of groundwater, for the rural and urban water supply in studied area. Normally, the alluvium as well as the volcanic rock units in the study area lacks primary porosity which limit the capacity to preserve groundwater. As a result, both rock units have low permeability which inhabits movement of groundwater, were insignificant units in the research site. In volcanic rocks fractures, vesicles and interflow sediments are main features for groundwater occurrence. From these structures fractures are dominant one in volcanic terrain for groundwater in studied area. From the geological data recorded during the many of the drilled boreholes, the basalt which lacks primary porosity has high secondary porosity due to intense weathering and fracturing through which the Shayaq Ali et al., Page No. 30

4 rainfall percolates and mixing with the composition of rock outcrops. So, it is a good aquifer in the area and influences groundwater quality. The vesicular basalt has high primary and secondary porosity and hence high permeability for groundwater movement and reserve. It has high groundwater potential. Springs are an important source of hydrologic information. They occur because hydraulic head in the aquifer system intersects the land surface. By paying attention to their distribution, flow characteristics, and water qualities, much valuable information can be derived without drilling a single well. Impervious Rock Springs (fracture springs) are recorded in the area from gentle slope of Nekemte highland. They are found in massive basalt which is highly fractured and jointed, the water movement through fractures and springs from where these fractures intersect the land surface at low elevations. Due to the differences in mineralogy, texture and structure of volcanic rocks water bearing quality and potential also varies. Groundwater quality in the volcanic rocks depends on the variety of rock formations as discussed in the next section. 6. Materials and Methods The aim of the sampling is to collect a portion of material small enough in volume to be transported conveniently and handled in the laboratory while still accurately representing the material to be sampled, [4]. The samples, however, have to be handled in such a way that no significant change in Table: 1 Selected Physico chemical and bacteriological water analysis results. Source sample Well Well Well Well Ethiopian Location Gidami Gulfa Shabo 2 nd Kejo Standard (mg/l) composition occurs before the analysis are made and due to probable seasonal variation in the water quality, in all, water samples from the 4 wells were collected for physicochemical analysis. The water samples were collected and stored in capacity clean plastic bottles [9] and before collection the bottles was carefully washed. In order to avoid any impurity, the wells were duly pumped so that the stagnant water is completely removed from site within well assembly. The water samples have been determined for the major constituents as per the methods prescribed (table-1) analysis of water samples for their major and few trace elements determined its quality for drinking purposes. 7. Water quality analysis The physico- chemical characteristic of water samples have been determined according to the standard methods of [5].The concentration of calcium, magnesium, bicarbonate, chloride and total hardness determined by titri-metric method. Calcium and magnesium determined by EDTA titration, for HCO3, Hcl titration to a methyl orange point. Chloride also determined by titration with AgNo3 solution. Flame emission photometry used for the determination of sodium and potassium. In this method water sample of the light emitted by a particular spectral line measured with the help of photoelectric cell and a galvanometer. Sulphate analyzed by gravimetric method. The concentration of nitrate and fluoride determine with the help of double beam U.V. spectrophotometer. WHO maximum allowable concentration (mg/l) T.D.S. (mg/l) (E.C) us/cm ph Sodium(mg/l Na) Potassium (mg/l K) Total hardness (mg/l caco 3) Calcium (mg/l Ca) Magnesium (mg/l Mg) Iron (mg/l Fe) Manganese (mg/l Mn) Trace Fluoride (mg/l F) Chloride (mg/l Cl) Nitrate (mg/l NO 3) Carbonate (mg/l CO 3) Nil Nil Nil Nil - - Bicarbonate (mg/l HCO 3) Sulphate (mg/l SO 4) Source: Water Mineral Energy Department, East Wollega zone, Nekemte Ethiopia 8. Results and Discussion 8.1. Hydrogen ion concentration (ph) The ph value of water indicates that the hydrogen ion concentration in water and is logarithm of [8, 9] reciprocals of their weight measured in milligrams per liter of water. When electrolyzed, the water is dissociated into two types of ions, i.e. positively charged hydrogen ion (H + ) and negatively charged Shayaq Ali et al., Page No. 31

5 hydroxyl ions (OH) causing acidity and alkalinity, respectively. It is claimed that at high ph levels, drinking water acquires a bitter taste and color intensity in a given water sample is increased by raising the ph. The ph value of acidic water varies from 0 to 7 and that of alkaline water between 7 and 14, while natural water has a ph value of 7.0. The fresh water has a ph dependent, occurring over the range , with an optimum ph of about 6.5.In all regions of the study area ph values are neutral conditions Electrical Conductance (EC) EC is a function of ionic concentrations and can be used for a quick assessment of dissolved substances in water. The importance of EC is its measure of salinity, which greatly affects the taste and thus has a significant importance on the user s acceptance of water as potable. It varies between 252 to 501 us/cm at 25oC in the study area. Electrical conductance of the water indicates that the groundwater is not highly mineralized and has a low content of dissolved salts in the study area Chloride (Cl) Cl is one of the major inorganic anion in water, and it is present in all potable water supplies and in sewage. High Cl in water give an undesirable taste to water and beverages and large amount may act corrosively and metal pipes and may be harmful to plant life. Chlorides in drinking water generally not harmful to human being until a high concentration is reached, although the chlorides may be injurious some people suffering from disease of heart and kidney. The chloride concentration in the study area is less than W.H.O. [1], permissible limits and is varies between 1.82 to 8.19 mg/l.(table1). The concentration of chloride corresponds with the E.C. value of groundwater is low with low EC value in the study area. A low concentration of chloride gives not salty taste to water Bicarbonate (HCO3) Bicarbonates and carbonates are the most common causes of alkalinity in natural water. The bicarbonate content in groundwater depends upon the partial pressure of the carbon dioxide in the soils and represents the major form since they are formed in considerable amount for the action of carbonates upon basic materials in soils. CO2 +H2O H + HCO3 CO2 + CaCO3 + H2O Ca HCO3 The main source of bicarbonate in groundwater include carbon dioxide in the soil, leaching from carbonaceous rock, carbon dioxide in the atmosphere and carbon dioxide released due to bacterial oxidation of organic matter. Carbonates are generally absent in shallow groundwater whereas bicarbonates range between to mg/l. in parts of the study area Hardness Water hardness is the traditional measure of a capacity of water to react with soap, hard water requiring a considerable amount of soap to water hardness is caused by dissolved solvent metallic ions. The fresh water, the principal hardness causing ions is calcium and magnesium, the ions strontium, iron, barium, and manganese also contribute. The value of total hardness in the ranges from to 230 mg/l. hence groundwater in part of study area is slightly hard to moderately hard. The value of total hardness is marked under the desirable limit of W.H.O. [1] in the study area Fluoride (F) The nation environment pollution due to fluoride (F) in groundwater is a matter of a great concern. As it possess serious consequences on human health. There is no wide variation of fluoride content in the study area, ranges between 0.50 to 0.54 mg/l. The whole study area is showing under the permissible limits of W.H.O. [1], drinking water standard Nitrate (NO3) Nitrates are widely present in substantial quantities in soil, in most waters, and in plants, including vegetables. Nitrates are products of oxidation of organic nitrogen by the bacteria present in soils and in water where sufficient oxygen is present. Nitrate contamination, often associated with agricultural activities, is a major problem in some shallow aquifer and is increasingly becoming a threat to groundwater supply. The nitrate content in groundwater in the study area varies from 0.35 to 60 mg/l. It is observed that all wells are having under the permissible limits of W.H.O. [1], drinking water standard, indicating no groundwater pollution. The higher nitrate concentration may be attributed due to combined effects of contamination from domestic sewage and runoff from fertilized fields. High level of nitrate has been responsible for cases of infantile methaemoglobinaemia and death Total Dissolved Solids (TDS) The TDS content of the groundwater are controlled by the chemical characters of groundwater and its ionic saturation status. The principal ions contributions to TDS are carbonate, bicarbonate, chloride, sulphate, nitrate, sodium, potassium, calcium and magnesium. The dissolution of solids in groundwater depends on their distribution and solubility, porosity and permeability of the rock, sub soil water and its flow path. The TDS content of the groundwater may increase at places where the Shayaq Ali et al., Page No. 32

6 chemical equilibrium has not attained between water and deposited salts. [8] have rated the palatability of drinking water according to the TDS level thus, excellent less than 300mg/l, good between 300 mg/l and 600mg/l, fair between 600mg/l to 900mg/l, poor between 900mg/l to 1200mg/l and unacceptable greater than 1200mg/l. The value of TDS in the study area ranges from 160mg/l to 310mg/l. The permissible limit of TDS is 1000mg/l, as per W.H.O. [1]. the value of TDS has been observed under the permissible limit, according to [6], the TDS level in excellent to good manner in all wells. Water with high concentration of TDS has laxative effect on people in the study area Sulphate (SO4) Sulphate appears in natural water in a wide range of concentrations and has no characteristic action on the soil other than increasing its salinity. The chief sources of sulphate in groundwater are sulphate minerals in sedimentary rocks, oxidation of sulphides from igneous rocks, addition of soil amendments such as gypsum, pyrites, fertilizers and rain water. In groundwater, sulphate generally occurs as soluble salts of calcium, magnesium and sodium. The analytical results of sulphate show concentration between 1.55mg/l to 36.05mg/l. in the study area. The concentration limit of sulphate in W.H.O [1], has prescribed highest desirable limits of 200mg/l and maximum permissible limit of 400mg/l in drinking water. High concentration of sulphates in association with sodium or magnesium in the drinking water may give gastrointestinal irritation Calcium (Ca) The calcium is one of the most important cations present in the groundwater. The main source of the calcium in groundwater are rainwater, leaching from fertilizers, soil, weathering of calcium, silicate minerals and use of surface water for irrigation, the dissolved CO2 control the calcium ions. The analytical results of sulphate show concentration between 15.20mg/l to 56.00mg/l in the study area. The highest desirable limit of calcium in drinking water is 75mg/l and a maximum permissible limit is 200mg/l W.H.O. [1], in drinking water. The value of the calcium ranges under the desirable limit of W.H.O [1], in the study area. High content is also harmful for kidney and bladder stones Magnesium (Mg) Magnesium is a common and moderately toxic element and Mg is one of the most important contributors to the hardness of water, the concentration of magnesium in groundwater is less than Ca. The analytical results of magnesium show concentration between 12.31mg/l to 26.88mg/l. in the study area. The value of W.H.O [1], has prescribed highest desirable limits of 50mg/l and maximum permissible limit of 150mg/l in drinking water. The main sources of mg are rainwater, weathering of mg, silicate mineral. Magnesium deficiency is associated with structural functional changes which may cause severe diarrhea, chronic renal failure and caloric malnutrition Sodium (Na) Sodium chloride is also used in the production of caustic soda, chlorine and many industrial chemicals. Significant quantities are used in the food processing, slaughtering and meat packing, dairy, fishing, grain and brewing industries, [7]. The concentration ranges between 7.10mg/l to 47.00mg/l. in the study area. The value of sodium W.H.O [1], has prescribed highest permissible limit of 200mg/l in drinking water. The concentration of sodium is observed under the permissible limit of W.H.O. in the study area in all the wells. Sodium is an essential element for human body, its higher content in drinking water may be harmful to a person suffering from cardio and renal diseases pertaining to circulatory system Potassium (K) Potassium is less common cations in the groundwater. Potassium salts are of the therapeutic value in the treatment of familiar periodic paralysis while no desirable or excessive limit for potassium have been set, though 10 mg/l 12 mg/l based on European Economic Community standard and 12mg/l of W.H.O. [1], the maximum permissible limit of potassium is 12 mg/l, the potassium ranges from 2.40mg/l to 6.0 mg/l in the study area. 9. Conclusions Groundwater is widely used for irrigation and domestic water need of the study area. Groundwater in the study area occurs in the weathered, fractured, jointed, vesicles, rocks. Groundwater mainly develops by dug wells. Thus geological structures play a major role in groundwater quality in the study area. The trend in the quality of groundwater is based on the chemical analysis data of water samples collected from different wells of the study area. It reveals that the groundwater quality has to improve all the study area because most of the wells have under the desirable limits of W.H.O [1] and Ethiopian Drinking water standards. There have not been many changes at all the wells in the study area. Shayaq Ali et al., Page No. 33

7 It has generally been observed that in the all sample under the permissible limit but also under the desirable limits. In all regions of the study area ph values are neutral conditions. The groundwater in part of study area is slightly hard to moderately hard. The concentration of chloride corresponds with the E.C. value of groundwater is low with low EC value in the study area. Magnesium deficiency is associated with structural functional changes in the study area, which may cause severe diarrhea, chronic renal failure and caloric malnutrition. In general all the major elements is under the desirable limits or below the required levels. According to W.H.O. standards the concentration in groundwater is not up to drinking standards for the human life in study area. 10. Recommendations: o Some required minerals are under the desirable limits but for human life the need of these minerals are not meeting in the permissible limits, hence the concentration of the minerals should be added up to permissible limits as per W.H.O standards for the human health. o The essential minerals are should be added to the desirable limits in the ground water to improve the quality for the drinking purpose. o The national and international agencies can help the improvement the ground water quality of the study area. 11. Acknowledgement Authors wish to thanks to officers, Water, Mineral and Energy Resources Department, East Wollega zone Nekemte for their cooperation in providing data to publish the research work. Thanks are also extended to Academic vice president, Wollega University for the administrative support and help rendered during the research work. 12. References 1. W.H.O. Guideline for drinking water quality, first addendum to third edition, Vol. 1, Recommendation, World Health Organization, Geneva, Switzerland, pp , Tamiru A. Ground water occurrence of Ethiopia M.Sc. thesis, Solomon and Mulugeta physiographic landforms of Nekemte area M.Sc. thesis, H.M Mengesha Tefera, Tadiwos Chernet and Workneh, Haro. Explanation to geological map of Ethiopia, Scale 1: 2,000,000, 2nd edition, APHA Standards methods for examination of water, 16 th Ed,AM Pub, Health Association Washington, USA, , Killin, A.F. Salt Canadian minerals year book, Ottawa, Department of Energy Mines and Resources, Canada, pp. 182, Bartarya S.K. Journal of Hydrogeology, , 6, Water well drilling and pumping test project in East Wollega zone, ORS. Addis Ababa. April, Pangaea drillers: well completion report in East Wollega zone, Addis Ababa, may Faure G. Principles and applications of Geochemistry, 2 nd ed. Prentice Hall, Englewood Cliffs, New jersey, USA, pp 53-57, Fetter, C.W. Applied Hydrogeology, Neril Pub. Co. A Well and Hawell Information Co. Colambia, USA, Prentice Hall, Englewood and Cliffs, New Jersey, USA, pp534, Wilcox, L.V. Guidelines for sodium percentage against E.C, New York, USA, pp 32-36, Shayaq Ali et al., Page No. 34