Groundwater Management Practice in Nairobi County

Abstract

Nairobi County falls in the greater Athi River Catchment. Its groundwater resources lie in the Nairobi Aquifer Suite (NAS) which is a group of multi-layered aquifers in the volcanic flows rising from the southern Aberdares, the Kikuyu Escarpment and Ngong Hills and dipping gently eastward into the pre-Tertiary Athi Lake Basin, terminating at the Mozambican Basement System (CCN, 2007; WRMA, n.d (a)). The county is Kenya’s economic hub employing about 25% of Kenya’s employed population and contributing to 45% of Kenya’s GDP. However in as much Nairobi is best served with infrastructure and utilities it faces challenges in providing adequate good quality water for its 3.1 million residents in 2009 who thus supplement the piped surface based supply with groundwater (UN Habitat 2006, Jacobsen et al, 2012). Groundwater was estimated to supply about 12.5% of the total daily demand, it’s sustainable management faces challenges of haphazard drilling, over-abstraction, pollution, weak legislative framework and enforcement of regulations (CCN, 2007; World Bank, 2011; Jacobsen et al, 2012; UN HABITAT, 2006; Caroline O. et al, 2012; Stephen F. and Albert T., 2005). This study documented management practices, trends and recommend the best way forward to manage groundwater in the county. It mapped 2,632 licensed boreholes and developed spatial discrimination maps; assessed trends in practices such as borehole locations, drilling depths and interviewed WRMA staff on compliance and challenges faced. A hotspots analysis was performed to elucidate statistically significant borehole density and water abstraction hotspots. Proximity analyses also showed a 6% increase in the number of boreholes that lie within 100 m from each other from 2011 to 2013 whereas analyses on drilling depths indicated that an average increase of 170 m from 1930 to 2013 and this was attributed to pollution of the upper aquifer and potentially competition for groundwater. This study also elucidated that the low level of compliance is mainly driven by the county’s population increase which drives other exigent contributing factors that include: increased water demand; intermittent piped supply; unclear legal framework; poor enforcement of supportive regulations; lack of a publicly available groundwater database for decision making; low capacity of the regulator; apparent groundwater availability that allows errant drillers to forego due processes, and low level of awareness of residents and borehole owners.