Groundwater exploitation in Southern Johor Bahru, Malaysia: Prospects and challenges while drilling and its mitigation measures

Exploration of groundwater sources are increasing worldwide due to the water scarcity. In this study, ground-water exploitation was carried out around Southern Johor Bahru in Malaysia, to understand the subsurface geology, identify potential high yielding aquifers, assess the drilling challenges and determine required miti-gation to deal with these challenges. Three exploratory wells were developed for this purpose; 2 wells located in volcanic-sedimentary rock and 1 in Older alluvium. It was found that the volcanic-sedimentary rocks have higher potential for groundwater extraction compared to Older alluvium in Southern Johor Bahru. The fracture with major opening (>4 cm) and litho-contact dominantly control the groundwater occurrence and productivity of volcanic-sedimentary rocks. In addition, the nature of fissures or fractures such as density and aperture influence the groundwater productivity. Whereas the primary porosity of rocks (<5%) is found not to control groundwater productivity except at completely weathered to residual soil zones (up to 47%). Also, the thickness of weathered layer does not substantially contribute to the groundwater productivity at the study area. The optimum depth for well development is more than 150 m for an approximate yield of 37-60 m3/hr at the study area. The length of casing is approximately 30 m depending on the thickness of weathered zone. Finally, the drilling issues such as air loss and mud loss were encountered in volcanic-sedimentary rock and Older Alluvium respectively.