Environmental Flow Assessments (EFAs) are becoming the global standard for determining the amount of water required to sustain aquatic ecosystems and sustain socio-economic development. EFAs comprise structured, science-based approaches to determine how much water must be left in the river to protect the aquatic ecosystems and achieve the desired ecological state. The building block methodology (BBM) that was used in this study is designed to identify a series of important flows (the building blocks) which will together provide the essential aspects of the natural hydrological regime that ensure the persistence of as much of the biodiversity as possible. The results show that a total inflow into eastern wetland of 5.52-6.81 m3 /s is required in order to sustain an outflow of 1-2 m3 /s past Ng’iriama and hence meet the “minimum” recommended flow rates further downstream at BBM1 and BBM2 during the drought low flow conditions. The rationale being that a satisfactory flow during drought low flow conditions will guarantee sufficient flows during low flow periods in normal and wet years. The low flows of 2.5 m3 /s and 19 m3 /s are recommended for the driest and wettest months, respectively.