Global Water Challenges of Food and Energy Systems in the 21st Century

Water is increasingly recognized as an important factor constraining humankind’s ability to meet its burgeoning food and energy needs. Water is a major factor limiting crop production in many regions around the world. Irrigation can greatly enhance crop yields, but the local availability and timing of freshwater resources constrains the ability of humanity to intensify food production. Water plays an important role in the production of energy, including unconventional fossil fuels extraction. Water is also important to meet climate change targets. Carbon capture and storage is broadly recognized as a technology that could play a key role in limiting the net anthropogenic carbon dioxide emissions from industrial and energy systems. However, carbon capture and storage technologies are energy-intensive processes that would require additional power generation and therefore additional water consumption for the cooling process./nWhile substantial additional water will be required to support future food and energy production, it is not clear whether and where local renewable water availability is sufficient to sustainably meet future water consumption. The extent to which irrigation can be sustainably expanded within presently rain-fed cultivated land without depleting environmental flows remains poorly understood. It also remains unclear where and to what extent new water demanding technologies such as carbon capture and storage and hydraulic fracturing might generate or exacerbate water scarcity./nIn this dissertation work, I used a global water balance model to determine at high spatio-temporal resolution local water demand and water availability for human societies. I was able to estimate if there is sufficient local water to sustainably meet future demand for water. I also determined the sustainability of these practices and the extent by which they deplete environmental flows and groundwater stocks./nI find that half of irrigation practices are currently unsustainable and that 15% of global unsustainable irrigation is embedded in international food trade. Despite widespread unsustainability from irrigation, I find that there is still substantial potential to increase food production by sustainably expanding irrigation over 140 Million hectares of croplands globally, potentially feeding 800 million more people. I also find that energy technologies such as hydraulic fracturing and carbon capture and storage will require substantial additional water, exacerbating water scarcity and creating a competition for the scarce local freshwater resources among energy, industrial, and agriculture industries. I show that certain geographies lack sufficient water resources to meet the additional water demands of carbon capture technologies and hydraulic fracturing./nThese findings shed light on the importance of freshwater in future decision making. The results of this dissertation have the potential to inform water, energy, and food security policies at global, regional, national, and local scales and to provide new insights to achieve global sustainability targets.

Advisor: D'Odorico, Paolo