Engineering Resilient Water Infrastructure Systems Under Deep Uncertainty: A Novel Framework Applied to Nigerian River Basins

This dissertation develops a novel engineering framework for designing and evaluating the resilience of water infrastructure systems under deep uncertainty in Nigerian river basins, addressing the inadequacy of conventional deterministic and single-scenario design approaches for a context where climate change trajectories, population growth, and land use futures are deeply uncertain. Water infrastructure in Nigeria faces a triple challenge of obsolete or absent existing infrastructure, rapidly growing demand, and deeply uncertain future conditions from climate change and socioeconomic development, all of which make the conventional design paradigm of sizing infrastructure for specific design conditions increasingly inappropriate. The theoretical contribution is a Decision Making Under Deep Uncertainty framework specifically adapted for the institutional and hydrological characteristics of Nigerian river basins, combining robust decision analysis methods including Info-Gap Decision Theory and Robust Optimisation with stakeholder-participatory scenario development and adaptive pathways planning. The framework is applied to two contrasting Nigerian water infrastructure cases: the expansion planning of the Ogun Reservoir and its water supply system serving Lagos, and the climate adaptation of the Hadejia-Nguru floodplain water management scheme in Jigawa and Yobe States. For each case, a performance model is developed that translates infrastructure investment decisions and scenario futures into performance indicators across water security, economic, ecological, and social dimensions. Robust investment strategies that perform satisfactorily across a wide range of plausible future scenarios are identified for both cases. Original contributions include the Nigeria-adapted DMDU framework, the adaptive pathways planning methodology for Nigerian institutional contexts, and the application findings for both case studies. Keywords: water infrastructure resilience, deep uncertainty, robust decision making, adaptive pathways, Nigeria.