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Methane Emissions from Artificial Waterbodies Dominate the Carbon Footprint of Irrigation: A Study of Transitions in the Food–Energy–Water–Climate Nexus (Spain, 1900–2014)

Aguilera, Eduardo, Vila-Traver, Jaime, Deemer, Bridget R., Infante-Amate, Juan, Guzmán, Gloria I., González de Molina, Manuel
Environmental science & technology 2019 v.53 no.9 pp. 5091-5101
carbon, carbon footprint, climate change, electricity generation, greenhouse gas emissions, industrialization, infrastructure, irrigation systems, mechanization, methane, methane production, power generation, surface water, uncertainty, water quality, water resources, water use efficiency, Mediterranean region, Spain
Irrigation in the Mediterranean region has been used for millennia and has greatly expanded with industrialization. Irrigation is critical for climate change adaptation, but it is also an important source of greenhouse gas emissions. This study analyzes the carbon (C) footprint of irrigation in Spain, covering the complete historical process of mechanization. A 21-fold total, 6-fold area-based, and 4-fold product-based increase in the carbon footprint was observed during the 20th century, despite an increase in water use efficiency. CH₄ emissions from waterbodies, which had not previously been considered in the C footprint of irrigation systems, dominated the emission budget during most of the analyzed period. Technologies to save water and tap new water resources greatly increased energy and infrastructure demand, while improvements in power generation efficiency had a limited influence on irrigation emissions. Electricity production from irrigation dams may contribute to climate change mitigation, but the amount produced in relation to that consumed in irrigation has greatly declined. High uncertainty in CH₄ emission estimates from waterbodies stresses a need for more spatially resolved data and an improved empirical knowledge of the links between water quality, water level fluctuations, and emissions at the regional scale.