Quantifying water-energy nexus for urban water systems: A case study of Addis Ababa city

Abstract

The complex interdependency between water and energy poses new challenges for policymakers to achieve a safe, secure, and sustainable supply of water and energy in the future. The water-energy nexus can be typically characterized by efficient use of energy and water resources. Hence, this paper aims to explore quantitative results of the nexus in terms of energy intensity on existing water systems within urban water cycles. The energy requirement for water treatment and water conveying to the city (from Legadadi water treatment, Gefersa water treatment and wastewater treatment area) as well as the energy requirement for water distribution within the city were quantified. The energy intensity for groundwater extraction, water transmission and water distribution were computed using Energy Intensity method. This led to identify the best technologies to insure the security of water-energy nexus. The annual energy demand and energy intensity values for groundwater extraction were estimated to be 0.6 PJ and 1.2 kWh/m3 respectively. These values for operating all pumps in the water transmission were 0.13 PJ and 0.32 kWh/m3 respectively. Similarly, the energy intensity value for water distribution was 0.27 kWh/m3 and distributes water to residential, commercial and industrial end-users. Determining the energy intensity predicts the future energy demand in urban water system. In 2030 and 2050, the predicted energy demand will be 0.50 and 0.83 PJ respectively for water transmission whereas it will be 0.41 and 0.67 PJ for water distribution.