Saturated Hydraulic Conductivities and High Yield Zones in the Phreatic Aquiferous Formations in Kumba – Cameroon: Determined From Slug-In Tests in Dug Wells
Kumba (latitudes: 4°36’-4°40’, longitudes: 9°23’- 9°29’), the economic capital of the Southwest Region- Cameroon, is located along the Cameroon Line at northwestern edge of the Douala Basin. This study aimed at determining the saturated hydraulic conductivities and high yield zones of the phreatic aquiferous formations in Kumba using slug-in tests in hand-dug wells, to guide the design and selection of sites for construction of wells capable of yielding pumping rates compatible with the users’ needs. A field geological mapping exercise was carried out in Kumba. There are over 4500 dug wells in Kumba. The wells are dug and completed according to the owner’s budget. Some have lids, other do not have collars, some have aprons, while others are inclined. Slugin tests were carried out at 11 sites using a 30 liters, 35 kg (45cm long 30cm diameter high pressure non deformable PVC round edged cylindrical water filled) slug. The quasisteady model of wellaquifer interaction for slug-in testing was adopted and spreadsheet interpretation by the Bouwer and Rice and Vivier methods gave minimum hydraulic conductivity values range from 2.88E-08m/d at Lawyer Enow to 1.60 E-06 m/d at New Quarters; and maximum values range from 1.81E-08 m/d at Lawyer Enow to 2.96E-06 m/d at New Quarters with an average of 2.41E-07 m/d. First estimates of dug well yields range from 2.36 m3 /d (at Akale Street) to 17.36 m3 /d (at New Quarters) with an average of 7.64 m3 /d with the relative high well yields zones at New Quarters, CCAS and Nkamlikum. The phreatic aquiferous formations in Kumba have averagely low saturated hydraulic conductivities with the lowest values at Lawyer Enow and the highest at New Quarters. The first estimations of well yields were lowest at Mile 1, Anglican, GS and Akale Street and highest at New Quarters, CCAS and Nkamlikum. These aquiferous formations are made up of dense clays, dense sandstones, dense limestones, dolomites, fractured gneisses, vesicular basalts, dense basalts and claystones layers with different permeabilities.