ABSTRACT:The extent and distribution of groundwater resources in parts of Anambra State, Nigeria has been investigated. The results show that the study area is directly underlain by four different geological formations including, Alluvial Plain Sands, Ogwashi-Asaba Formation, Ameki/Nanka Sands and Imo Shale, with varying water storage and yielding capacities. Borehole depths within the Alluvial Plain Sands are shallow (5-30m) yet the sands are excellent aquifers with high yields (3-5 litres/sec) especially along the Anambra West -OnitshaOgbaru L.G.A. axis. Elsewhere the yield is low (about 0.5litres/sec) and may dry up at peak dry season periods. The Ogwashi-Asaba Formation occurs in a north-southerly trend and underlies Ekwusigo, Nnewi North and South and Ihiala Local Government Areas. This formation consists of multiple aquifers and a depth to water table ranging from 50 to 110m. Within it, transmissivity values of 37.54 to 95.5m 2
ABSTRACT:The elements of water budget equation were analyzed for the Agulu lake area and underlying aquifers. The water budget implications for soil and gully erosion were evaluated in relation to the geological formations and hydrogeotechnics. Results show that rainfall constitutes the main source of precipitation. It ranges from 1714.04mm to 1995.53mm annually. The potential groundwater aquifer volume is 1.5 X 10 7 m 3 . Discharge from aquifers contributes 7.4 X 10 7 m 3 water annually. The amount of 1.72 X 10 5 m 3 that is 60% of precipitation is lost to evaporation; 17 to 21% to infiltration. The quasi steady state of the lake water level and volume shows surface and groundwater continuity as explained by the small difference between total input and output values of the computed water budget of the lake and the aquifer. Flood studies indicate that 19.5% of the annual precipitation constitutes runoff, the main agent of gully and soil erosion, flooding and landslides. The other factors that control the distribution and location of gullies are lithologic and stratigraphical, while topography/geomorphology controls gully distribution within various geologic units. A typical gully is about 500m X 50m X 30m long, wide and deep respectively. The destruction to life and property by runoffs/floods demands joint and sustained efforts by the community dwellers,
Eighteen (18) water boreholes were studied for lost circulation. When locations of the boreholes associated with lost circulation were plotted on the map of Anambra State a lost circulation belt was observed around the River Niger -Onitsha -Oba -Nnewi axis. Lost circulation intervals range between 20-50m and 75-90m depth and were found to be associated with lignite and peaty clay members of the Ogwashi-Asaba Formation and/or the Ameki/Bende Formation. This suggests that natural rather than anthropogenic factors are responsible for the widespread occurrence of lost circulation in the State, although the latter could aggravate the former. Lignite and peaty clay of the Ogwashi-Asaba and Ameki/Bende Formation cause lost circulation because they are woody to earthy in nature and are easily eroded when they occur above the water table. These conditions favour the development of vugs, leading to increase in permeability and porosity, making the formation prone to lost circulation. Pre-drilling geophysical, geological and hydrogeological investigations are recommended, since these would go a long way to identify the presence or absence of lignite and thus help to avert possible lost circulation intervals. @j JASEM
INTRODUCTION he project area is located within Anambra State, Southeastern Nigeria and lies within latitudes 5°560 1 and 6°40 1 N and longitude, 7°00 1 and 7°100 1 E, encompassing Aguata, Aniocha and Orumba Local Government Area. These areas hydrologically fallwithin the Anambra Basin and more specifically within the Anambra River Basin (Fig. 1). The area hasabundant surface water and groundwater resources. The main river systems in the study areas are Odo, Obizi, Otalulu, Iyiagu and Uchu. Geology and hydrogeology The Anambra basin is one of the major inland sedimentary basins in Nigeria, which is bounded on the east by the Abakaliki anticlinorium and on the southwesterly direction by the Benin hinge-line, the limits of the Eocene growth faults of the Niger Delta. These growth faults extend from the Calabar hinge-line to the T ABSTRACT Water quality (physico-chemical and biological) of the aquifers of the Tertiary formation of Igboukwu and environs was evaluated using the World Health Organization (WHO) and Nigeria Standard for Drinking Water Quality guidelines with water samples collected from twenty boreholes during pumping tests. The study area covers a total surface area of 450.56km 2 including towns like, Igboukwu, Ezinifite, Uga, Ekwulobia, Nanka, Oko, Aguluezechukwu, Umuchu, Achina, Ekwulumili and Ndiowu. Results showed that the area is underlain by two geological Units, Imo Shale and Nanka Sands, from which the aquifers were tapped. Analysis of the results of physical parameters showed that temperature is ambient, water is colourless, odourless and tasteless for all samples studied. Results of the water chemistry, however showed marked variations; pH values ranged from 5.20 at Ihuowelle Igboukwu to 6.80, at Ebele Achina (highest), total dissolved solids (TDS) from 11.20mg/l at Ezinifite to 71.40mg/ at Achina, turbidity nil, major cations and anions, calcium (Ca 2+) ranged from 5.0mg/l at Okwuchiezeada Ezinifite to 42mg/l at Ndiowu, magnesium (Mg 2+) ranged from 0.01mg/l at Uga to 0.18mg/l in Ekwulobia. Iron ion values ranged from 0.02mg/l to 0.35mg/l in Igboukwu, Umueze Uga (0.35mg/l), manganese, copper and residual chlorine were not detected; while Bicarbonate (HC03) ranged from 7.00mg/l at Ezinifite to 58.00mg/l at Uga and Sulphate (SO4 2) ranged from 0.00mg/l at Igboukwu to 7.00 mg/l at Ekwulobia, sulphate ions were not detected in Ekwoulobia, while in Umunze and Uga, Mn 2+, Ca 2+ and Clions were not detected either. Bacteriological results showed that total coliform and fecal coliform were zero. These results thus showed that the aquifers in the study areas contain portable water for domestic use if the wells are well constructed and harnessed.
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