Water-Energy-Climate Nexus CDMX

Global urbanisation is rapidly developing, with an expected seven billion urban residents by 2050. This rapid growth will put considerable stress on both water and energy resources in cities. While there is much research at the national and regional levels on the energy implications of water supply (the urban water-energy-climate ‘nexus’), there is relatively little at the city scale. In this paper, a city-level study of the urban water-energy-climate nexus is presented for México City (CDMX). It is shown that at present 50% of CDMX water (city total c. 1000 x 106 m3 yr-1) comes from a local aquifer with a further 30% deriving from energy-intensive surface sources which are pumped over considerable topography. The water supply system consumes currently 90% of the water system energy demand (city total c. 2500 x 106 kWh yr-1), and is responsible for the majority (90%) of the CO2e emissions (city total c. 750-2000 x 106 kg CO2e yr-1). In the wastewater sector, 80-90% is discharged with no or little treatment, with corresponding low energy demand. The small fraction that is treated accounts for the vast majority of energy use in the wastewater sector. This study also shows the uncertainty in energy demand and CO2e emissions when reliant on secondary data as it´s considerable over/under-estimated energy used compared with primary data. Three water savings mesaures are assessed for their impact on energy and CO2e emissions reductions. Considerable reductions in water supply volumes and concomitant energy consumption and CO2e emissions are possible. However the extent of implementation, and the effectiveness of any implemented solutions depend on financing, institutional backing and public support. Additional climate impacts are explored taking particular attention to water security, flood capacity enhancement and CO2 abatement to evaluate adaptation-mitigation interrelations. This work adds important city-level quantification of the urban water-energy-climate nexus, allowing operators and policy makers to discern which water-system elements are responsible for the greatest energy use and climate impact, and are therefore better equipped to make targeted operational decisions.