In Kenya, as in much of Africa, there is significant growth in water-reliant industry. In 2016-17 much of East Africa was affected by a severe drought. During such events, groundwater resources can act as a buffered resource, but may themselves be stressed by reduced recharge and increased abstraction, posing significant challenges to water resource management. Despite the importance of groundwater use in the continent, there is a lack of knowledge of the groundwater hydrodynamics of many African aquifers. The aim of this study is to characterise the groundwater system in Kwale County in south-eastern Kenya, examining the possible influence of increased abstraction by new industry and agriculture and determine the effects of the 2016-17 La Niña drought. This area has been selected as an aquifer representative of much of coastal East Africa, where new water-reliant activities (mining and irrigated sugar) were established in 2012-2013; these coexist with the long-standing tourism industry and local communities.
Diverse hydrochemical, isotopic, geophysics and groundwater level measurements were carried out to study the groundwater hydrodynamics and characterise the aquifer system before and during the drought period. The recharge in the study area was estimated using the soil mass balance. Due to the difficulties in obtaining good abstraction data, different information sources were used to determine the groundwater abstraction of the different water-reliant industries. These included direct information from the companies and using Google Earth, Trip Advisor and interviews to define hotel abstractions.
The results show that the current level of groundwater abstraction does not significantly affect aquifer water levels. However, during la Niña there was a 69% reduction in recharge compared with an ‘average’ climate year. Furthermore, there was a concurrent increase in seawater intrusion even during the wet season. The main impact occurred to community handpumps, prone to drying up during drought periods, as they exploit a shallow aquifer that is less resilient to drought. On the contrary, groundwater abstraction by irrigated agriculture and mining is from the deep aquifer, which is more resilient to the drought periods common in the area.
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).