The book addresses the challenges of urban water security and adaptive management in Sub-Saharan Africa, exploring and interlinking novel concepts of ecosystems services, watershed investments, and boundary work. Specifically, the book's goals are to (i) present a conceptual framework for the urban water sector from an ecosystem services perspective, highlighting the specificities of the Sub-Saharan context; (ii) develop an operational approach to designing and assessing the impacts of watershed investments, based on ecosystem services and boundary work; and (iii) test the approach through a case study in Asmara, Eritrea, and discuss the findings and lessons learned that can be applied in other contexts. Through a fully worked out case study, from identification of water challenges and opportunities to spatially explicit modelling, the book offers a sound and accessible, coverage of issues and proposed solutions to better operationalize ecosystem services, watershed investments and boundary work, to promote adaptive management, and achieve water security in the context of rapidly developing cities in Sub-Saharan Africa. The book is an effective tool for capacity building of diverse stakeholders on the urban water sector, including water managers, local and national policy-makers as well as a suitable resource for both undergraduate and post-graduate courses in planning and geography.