Africa's economic and population growth prospects are likely to increase energy and water demands. This quantitative study shows that pathways towards decarbonization of the energy sector in Africa may lead to higher water withdrawals and consumption than expected. By 2065, investments in low-carbon energy infrastructure increase annual withdrawals from 1% (2.0oC) to 2% (1.5oC) of total renewable water resources compared to 3% in the baseline scenario, despite lower final energy demands in the mitigation scenarios. Water consumption, in comparison to the baseline, increases by 282% (2.0oC) and 300% (1.5oC) by 2065, due to the high water-intensity of the low-carbon energy system. To meet the 1.5oC pathway, the energy sector requires higher water consumption overall and per unit of energy than other scenarios. These findings demonstrate the crucial role of integrated energy planning and water resources management if Africa is to achieve climate-compatible growth.

Energy security for the EU is a priority of the European Commission. Although both blue and green water resources are increasingly scarce, the EU currently does not explicitly account for water resource use in its energy related policies. Here we quantify the freshwater resources required to produce the different energy sources in the EU, by means of the water footprint (WF) concept. We conduct the most geographically detailed consumptive WF assessment for the EU to date, based on the newest spatial databases of energy sources. We calculate that fossil fuels and nuclear energy are moderate water users (136-627 m 3 /terajoules (m 3 TJ -1 )). Of the renewable energy sources, wood, reservoir hydropower and first generation biofuels require large water amounts (9114-137 624 m 3 TJ -1 ). The most water efficient are solar, wind, geothermal and run-of-river hydropower (1-117 m 3 TJ -1 ). For the EU territory for the year 2015, our geographically detailed assessment results in a WF of energy production from domestic water resources of 198 km 3 , or 1068 litres per person per day. The WF of energy consumption is larger as the EU is to a high level dependent on imports for its energy supply, amounting to 242 km 3 per year, or 1301 litres per person per day. The WF of energy production within the 281 EU statistical NUTS-2 (Nomenclature of Territorial Units for Statistics) regions shows spatially heterogeneous values. Different energy sources produced and consumed in the EU contribute to and are produced under average annual and monthly blue water stress and green water scarcity. The amount of production under WS is especially high during summer months. Imported energy sources are also partly produced under WS, revealing risks to EU energy security due to externalisation. For the EU, to decarbonise and increase the share of renewables of its energy supply, it needs to formulate policies that take the water use of energy sources into account. In doing so, the spatial and temporal characteristics of water use and water stress should particularly be considered.

Africa’s economic and population growth prospects are likely to increase energy and water demands. This quantitative study shows that energy decarbonisation pathways reduce both water withdrawals and water consumption relative to the baseline scenario. However, the more aggressive decarbonisation pathway (1.5oC) leads to higher overall water withdrawals than the 2.0oC scenario but lower water consumption levels by 2065. By 2065, investments in low-carbon energy infrastructure increase annual water withdrawals from 1% (52bcm) in the 2.0oC to 2% (85bcm) in the 1.5oC scenarios of total renewable water resources in Africa compared to 3% (159bcm) in the baseline scenario with lower final energy demands in the mitigation scenarios. Water consumption decreases from 1.2bcm in the 2.0oC to 1bcm in the 1.5oC scenario, compared to 2.2bcm in the baseline scenario by 2065, due to the lower water intensity of the low-carbon energy systems. To meet the 1.5oC pathway, the energy sector requires a higher water withdrawal than the 2.0oC scenario, both in total and per unit of final energy. Overall, these findings demonstrate the crucial role of integrated water-energy planning, and the need for joined-up carbon policy and water resources management for the continent to achieve climate-compatible growth.