A spatial and temporal assessment of resource security in the water, energy, food and waste nexus in Spain

The effects of climate change, such as droughts and decreased rainfall, as well as population growth and glob-alization are aggravating the availability of water, energy and food. As a result, meeting the population's demand will be a major challenge in the near future. For this reason, assessing the situation of the water-energy-food (WEF) nexus is of great importance to know the vulnerabilities of the system and take actions to correct or improve them. The contribution of this work is the formulation of a composite index called the WEF-Waste index that includes 13 indicators, 4 of which are indicators to measure aspects of the water sector that include availability, independence, treatment and recycling; 3 energy indicators that include availability, independence and renewable energy; 4 food indicators that measure availability, food independence, ecological area planted and food waste; and 2 urban solid waste indicators that measure the level of separation and reuse. The WEF-Waste index was evaluated in Spain at the national level and in the 17 autonomous communities over a period of 10 years in order to focus on the spatial and temporal distribution pattern of the WEF nexus. Results show that the indicator with the lowest scores over the years was water availability, which indicates a very important water deficiency. On the other hand, high values in the water treatment indicator were obtained, showing that a high percentage of the water supplied to the network and used is processed in wastewater treatment plants. The WEF-Waste index has an improving trend from 2010 to 2014. However, by 2016 it suffered a decay and from that year to 2020, it again presented a positive trend in the scores of the communities.