The Characterisation of Water Scarcity: Developing a Storage-based Indicator Framework for the Great Ruaha River Catchment, Tanzania

This thesis addresses a fundamental lack of critical research investigating the meaning and practical application of widely used water scarcity metrics that include the Falkenmark Water Stress Index (WSI) and the Water Withdrawal to Availability (WTA) ratio. Recognising that current indicators do not account for the significant inter- and intra-annual variability in freshwater resources, this research proposes a new methodology to characterise water scarcity that explicitly considers the contribution of water storage to freshwater availability. This approach also specifically addresses common assumptions of domestic water demands (i.e. ~100 litres capita day (LCPD)) and adaptive strategies that people employ to maintain access to freshwater. Central to the arguments presented in this thesis is a case-study from the semi-arid Great Ruaha River Catchment (GRRC) in Tanzania. Application of the two metrics to the GRRC provide contrasting results, despite an absence of river discharge for an increasing period of the year. Investigating the strong inter-annual variability of freshwater availability suggests that naturally-occurring shifts in upstream hydrology may have a greater impact on downstream zero-flows than previously suggested, bringing into question the predominant narrative that livestock keepers and irrigation has constituted the primary cause for the experienced water shortages. Fieldwork, informed by a mixed-methods approach, quantifies domestic water demand in three villages to show that domestic water use is significantly lower than the assumed ~100 LCPD embedded in the WSI. Analysing the pathways to accessing the varying water available in the same villages show that development interventions which did not follow participatory approaches, failed. As a response to the resulting lack of clarity over water infrastructure ownership, informal pathways emerge through self-supply water storage systems such as hand-dug wells. Such systems are not uncommon in sub-Saharan Africa but remain inadequately represented in water scarcity metrics. Finally, the research considers what an indicator approach that is informed by inter- and intra-annual contributions of storage to freshwater availability could look like and evaluates the current limitations to its implementation