Water is a basic human need—to both provide hydration and grow food. Clean water supports healthy ecosystems, which provide important goods and services for human consumption and enjoyment. Water is also essential to meet modern needs—to generate the energy required to heat and cool homes, process transportation fuels, manufacture and transport the goods we consume and support communication networks. With the threats of climate change and a growing global population, the demand for clean and reliable water supplies is on the rise. As water is essential for people, ecosystems, and industries, this valuable resource is central to the energy-water-food nexus.
Energy Use for Water
A key consideration for water is not just the quantity available but also whether the quality of the water is suitable for its intended purpose. Extreme climate conditions, such as drought or flooding, and human activity, such as fracking or agricultural pesticide use, all impact the quality of water available for use. As water quality deteriorates, there is a greater need for highly energy intensive treatment technologies, such as desalination of drinking water and ultraviolet disinfection of wastewater to make the water suitable for people and receiving waters. Drinking water and wastewater plants represent some of the largest energy consumption for local governments, accounting for 30%–40% of total energy consumed (“State and Local Climate Energy Program,” U.S. Environmental Protection Agency, State and Local Climate Energy Program). According to the International Energy Agency’s World Energy Outlook 2016 (p. 379), the water sector’s share of global electricity consumption is projected to be around 4% by 2040, which is roughly equal to the total energy consumption of Australia. However, in regions highly reliant on desalination, such as the Middle East, the electricity share is projected to increase from 9% in 2015 to 16% by 2040. Globally, of the electricity consumed for water, approximately 40% is used to extract ground and surface water, 25% is used for wastewater treatment and 20% is used for water distribution (World Energy Outlook 2016, p.347).
Energy use for water topics identify key considerations pertaining to the use of energy as an input to the water and wastewater sectors, including energy use for pumping, treatment, distribution, and conveyance of water and wastewater; water and wastewater system optimization and energy recovery; water quality, effluent quality, fit-for-purpose water, water efficiency, access to clean and reliable water supplies, urbanization, access to hygiene and sanitation, water system loss, energy efficiency, and demand response.
Food Sector for Water
Food for water topics identify key considerations pertaining to food or land as it influences the water and wastewater sectors. Land-use decisions pertaining to development density, plant and material selection, areas impervious to water infiltration, and irrigation practices, all affect the flow and resulting quality of runoff water, impacting surrounding ecosystems and receiving waters. “Declining water quality has become a global issue of concern as human populations grow, industrial and agricultural activities expand, and climate change threatens to cause major alterations to the hydrological cycle” (“Water Quality,” International Decade for Water for Life 2005–2015, United Nations). In particular, human activities such as fertilizer and pesticide use for agriculture, directly impact the quality of runoff and the quality of water available for people and ecosystems. Irrigated agriculture is the world’s largest water user, accounting for roughly 70% of total global freshwater withdrawals—and up to 85% in some developing countries (World Energy Outlook 2016, p.351). Urbanization trends are also putting increasing demands on water while also impacting raw water quality and availability.
Land use impacts for water topics identify key considerations pertaining to the impact of land use practices on the water and wastewater sectors, including water rights, watersheds, ecosystems, crop and plant selection, land use planning, urbanization, impervious area, material selection, irrigation practices, stormwater runoff, nonpoint-source pollution, and biofuels.
Water is essential to the extraction of raw materials, and the processing, manufacture, and transport of goods. The main water consuming industries are discussed in under industry impacts, which include agriculture, thermoelectric power, and manufacturing. Industry is the second largest water consuming sector, after agricultural water use. In 2014, nearly 10% of global water withdrawals were for industrial use. This share is projected to remain steady over the next twenty years (World Energy Outlook 2016, p.352).
The water sector includes policies and best practices as they relate to the following key topics: