Climate change and future developments can influence the availability of groundwater resources for water supply. To mitigate their effects on aquifers systems and the dependent human communities and industrial activities in Africa, it is relevant to consider them in long-term water management plans. In order to advance this understanding, this study described here evaluates the effect of climate change and anticipated increased groundwater demand from a coastal aquifer located in southern Kenya (Kwale County). A previously calibrated numerical groundwater flow model has been used as an assessment tool to study how future climate (precipitation and temperature variation) and groundwater abstraction changes will affect the aquifer system. The groundwater flow model was constructed using Modflow-2005 to simulate the period 2010 to 2017, and 8 future model scenarios developed that cover the hypothetical years from 2018 to 2023. Future rainfall scenarios have been constructed based on long historical data series (from 1959 to 2017) and the Standard Precipitation Index. Future abstraction has been based on current abstraction and future estimations made by to Water Resources Authority water allocations. The main results show that in a succession of prolonged dry seasons the groundwater level decline in the shallow aquifer can reach five meters, with important implications for local community water supplies. Effective recharge depends on precipitation distribution throughout the year, with important implications for both dry periods and also for "average rainfall years". The most significant groundwater decline in drought periods is observed in the vicinity of the pumping deep aquifers wellfields, where the effects of drought and significant abstraction are multiplied. However, the effect of increased abstraction on the shallow aquifer system is limited. Despite groundwater level decline observed during prolonged dry periods, a dry period followed by a humid period leads to the relatively swift recovery of the groundwater system.
The authors gratefully acknowledge the support of Kenya's Water Resource Authority (formerly WRA), the Kwale Country Government, Base Titanium Ltd., Kwale International Sugar Company Ltd. and Rural Focus Ltd. This research was funded by the UK Government via NERC, ESRC and DFID as part of the Gro for GooD project (UPGro Consortium Grant: NE/M008894/1).