Many towns in Kenya’s arid and semi-arid lands (and to a lesser extent, sub-humid zones) rely largely or exclusively on groundwater for public and private water supply. Urban water service delivery in such areas faces significant challenges through the intersection of higher poverty rates, inadequate and more variable water sources, smaller towns with lower economies of scale, institutional barriers/low capacities, and increasing anthropogenic pressures and climate variability (which influence groundwater recharge and quality). The juxtaposition of on-site sanitation facilities and groundwater wells, coupled with lack of adequate assessment and monitoring of groundwater resources, has resulted in uncertainty as to whether or not the water being consumed is safe, and has also resulted in poor attention being paid to groundwater planning at all levels. The main objective of this study is to use scientific evidence, from a transdisciplinary perspective, to inform policies and practices that would sustain the quality of urban water supply systems in these fragile regions in the face of rapidly increasing urbanisation and climate change. Biophysical and socio-economic data is currently being collected in the two study sites under two projects: (1) the REACH Programme (www.reachwater.org.uk) and AfriWatSan Project (www.afriwatsan.org) and will be analysed during the Fellowship period. The expected outcome is that institutions and communities will work together, on a firm science-evidence base, to protect and sustain the groundwater resource for present and future generations.