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Assessing the Suitability of Hand Drilling Techniques for Abstracting Shallow Alluvial Aquifers Along River Benue Floodplain, Yola North Eastern Nigeria Buba A. Ankidawa 1 , Jackson M. Ishaku 2 and Joseph A. Tanko 3 1. Department of Agric. & Environmental Engineering, SEET, Modibbo Adama University of Technology, PMB 2076, Yola, Nigeria 2. Department of Geology, SPAS, Modibbo Adama University of Technology, PMB 2076, Yola, Nigeria. 3. Department of Civil Engineering, SEET, Modibbo Adama University of Technology, PMB 2076, Yola, Nigeria. INTRODUCTION • In Nigeria and most of African countries, groundwater abstraction for water supply and irrigation has traditionally been through hand dug wells (Adekile & Olabode, 2009). • Manually-drilled wells for water supply or irrigation purposes are more affordable than machine-drilled wells and more productive than hand-dug wells, thereby providing access to improved sustainable water points at a lower. • Manual drilling is a practical solution for tube wells less than 40 metres deep in alluvial soils. • In Adamawa State, such alluvial formations are found along River Benue flood plains, where most of the farmers practice irrigation during the dry season period Aim of the Research The aim of the research is to quantify the maximum drilling depths required at the peak period of the dry season for the application of hand drilling techniques Figure 1: Geological map of the study area MATERIALS AND METHODS Materials and methods adopted for the research involves collecting data as follows: 1. Determining elevation 2. Determining the maximum depth using augering method 3. Pumping test for estimating aquifer parameters 4. Field Shear Vane Tester Figure 2: Determining elevation across the floodplain Figure 3: Borehole drilling using hand augering method Figure 4: Pumping test carried out in the field Figure 5:Using Field Shear Vane Tester to determine shear force on sediments, RESULTS Figure 6: Topographic map of the study area Pumping station Hydraulic conductivity (m/day) Transmissivity (m 2 /day) Specific yield (m 3 /day) Well 1 4,095.4 1,149.1 864 Well 2 1,849 881.3 864 Well 3 10,800 4,017.6 3,456 Well 4 11,750.4 5,667.8 6,048 Well 5 8,121.6 4,009 3,456 Well 6 34,646.4 11,577.6 11,232 Well 7 5,581.4 2,151.4 1,728 Well 8 4,147.2 2,816.6 2,592 Well 9 13,478.4 6,842.9 6,048 Well 10 4,933.4 1,892.2 1,728 Well 11 14,169.6 5,195.4 5,184 Well 12 9,158.4 4,657 3,456 Mean 10,195.2 4,233.6 4,320 Figure 7: Lithologic sections of the alluvial floodplain (with overlying curve), from twelve hand drilled boreholes along a 2,500 m transects from River Benue (Ankidawa, 2015a) Shear strength are Harder at the top and lower at bottom, and harder when moving away from River Benue. Figure 8: Shear strength forces on sediments at twelve borehole locations (1 to 12), with their lithologic descriptions in the floodplain (Ankidawa, 2016). Table 1: Estimated hydraulic conductivity, transmissivity and specific yield at the twelve pumping wells CONCLUSION The floodplain elevation variations are relevant in precisely estimating groundwater level, which will be useful for application of hand drilling technique. Drill logs obtained across the floodplain are within the depth for abstraction with the hand drilling techniques. The floodplain has high transmissivity which gives good yield to the shallow wells for abstraction for water supply. The results of Field Shear Vane Tester (FSVT) on the floodplain have identified suitable locations for drilling, especially using hand drilling method that uses human power. References Ankidawa, B.A. (2015a) Assessing the sedimentology along River Benue Floodplain for application using manual drilling, North Eastern Nigeria. Journal of Basic and Applied Research International, vol. 7(4), p. 211 – 219. Ankidawa, B.A. (2015b). Shear Strength Force Estimation on the Alluvial Sediments in Relation to Manual Drilling: The Case of Upper Benue River Floodplain, North Eastern Nigeria. Nigerian Journal of Engineering Science and Technology Research, vol. 2(1), p. 97 – 109. Adekile, D. and Olabole, O. (2009). Hand Drilling in Nigeria. Why kill an ant with a sledgehammer. Rural Water Supply Network. Field Note UNICEF l, (2009) vol. 1, p. 3 – 7. The lithologic sections show clayey silt, sandy silt and sand deposits with sandy silt sediments as major composition of the floodplain. The hydraulic conductivity results range from 1,849 to 34,646.4 m/day with a mean value of 10,195.2m/day, indicating that the floodplain formations are highly permeable and can recharge the shallow alluvial aquifers for abstraction using hand drilling techniques
