Patterns of Use
All life on Earth depends on water. Human uses include drinking, bathing, crop irrigation, electricity generation, and industrial activity. For some of these uses, the available water requires treatment prior to use. Over the last century, the primary goals of water treatment have remained the same—to produce water that is biologically and chemically safe, appealing to consumers, and non-corrosive and non-scaling.
- In 2015, total U.S. water use was approximately 322 billion gallons per day (Bgal/d), 87% of which was freshwater. Thermoelectric power (133 Bgal/d) and irrigation (118 Bgal/d) accounted for the largest withdrawals.1 Water for thermoelectric power is used to cool the steam that drives electric generators. Though 41% of daily water use is for power generation, only 3% of these withdrawals are consumptive.1 Irrigation includes water applied to agricultural crops along with the water used for landscaping, golf courses, parks, etc.1
- In 2015, California and Texas accounted for 16% of U.S. water withdrawals.1 These states along with Idaho, Florida, Arkansas, New York, Illinois, Colorado, North Carolina, Michigan, Montana, and Nebraska account for more than 50% of U.S. withdrawls.1 Florida, New York and Maryland accounted for 1/2 of saline water withdrawals.1
Estimated Uses of Water, 20151
Sources of Water
- Approximately 87% of the U.S. population relied on public water supply in 2015; the remainder relies on water from domestic wells.1
- Surface sources account for 74% of all water withdrawals.1
- About 153,000 publicly owned water systems provided piped water for human consumption in 2011, of which roughly 51,000 (34%) are community water systems (CWSs).2 8% of all CWSs provide water to 82% of the population.3
- In 2006, CWSs delivered an average of 96,000 gallons per year to each residential connection and 797,000 gallons per year to non-residential connections.4
Sources of Water Withdrawals1
- 2% of total U.S. electricity use goes towards moving and treating water and wastewater, a 52% increase in electricity use since 1996.3 Most cities use 3,300-3,600 kWh/million gallons of water delivered and treated.5 Electricity use accounts for around 80% of municipal water processing and distribution costs.6
- Groundwater supply from public sources requires 2,100 kWh/million gallons—about 31% more electricity than surface water supply, mainly due to higher raw water pumping requirements for groundwater systems.3
- The California State Water Project is the largest single user of energy in California, consuming 5 billion kWh per year, on average—more than 25% of the total electricity consumption for the entire state of New Mexico. In the process of delivering water from the San Francisco Bay-Delta to Southern California, the project uses 2%-3% of all electricity consumed in the state.7
- The Safe Drinking Water Act (SDWA), enacted in 1974 and amended in 1986 and 1996, regulates contaminants in public water supplies, provides funding for infrastructure projects, protects sources of drinking water, and promotes the capacity of water systems to comply with SDWA regulations.8
- Typical parameters that the U.S.EPA uses to monitor the quality of drinking water include: microorganisms, disinfectants, radionuclides, organic and inorganic compounds.9
- Of all CWSs, 91% are designed to disinfect water, 23% are designed to remove or sequester iron, 13% are designed to remove or sequester manganese, and 21% are designed for corrosion control.4
Size Categories of Community Water Systems2
Life Cycle Impacts
- The 2015 Drinking Water Infrastructure Needs Survey and Assessment found that U.S. water systems need to invest $472.6 billion over the next 20 years to continue providing clean safe drinking water.10
- 66% ($312.6 billion) of the total national investment need is for transmission and distribution. The remaining 34% of need is for treatment ($83.0 billion), storage ($47.6 billion), source development ($21.8 billion), and other systems ($7.5 billion).10
- Water systems maintain more than 2 million miles of distribution mains.11 In 2000, nearly 80% of systems were less than 40 years old, while 4% were more than 80 years old.12 200,000 main breaks occur each year in the US, disrupting supply and risking contamination of drinking water.13
Total 20-Year Need, by Project Type10
- Supplying fresh water to public agencies required about 39 billion kWh of electricity in 2011. This energy intensity increased by 39% beyond the 1996 values, mostly due to population growth and expansion of treatment facilities. This trend will likely continue in the coming years.3
- Household appliances contribute greatly to the energy burden. Dishwashers, showers, and faucets require 0.312 kWh/gallon, 0.143 kWh/gallon, and 0.139 kWh/gallon, respectively.14
Life cycle energy use for ann arbor water treatment plant14
- Consumptive use is an activity that draws water from a source within a basin and returns only a portion or none of the withdrawn water to the basin. The water might have been lost to evaporation, incorporated into a product such as a beverage and shipped out of the basin, or transpired into the atmosphere through the natural action of plants and leaves.1
- Agriculture accounts for the largest loss of water (80-90% of total U.S. consumptive water use).16 Of the 118 Bgal/d freshwater withdrawn for irrigation, over half is lost as a consequence of consumptive use.1 Of the 133 Bgal/d of water withdrawn for thermoelectric power in the U.S., 3% is consumed (4.31 Bgal/d).1
Solutions and Sustainable Alternatives
- Major components that offer significant energy efficiency improvement opportunities include pumping systems, pumps, and motors.17
- Periodic rehabilitation, repair, and replacement of water distribution infrastructure would help improve water quality and avoid leaks.10
- Right-sizing, upgrading to energy efficient equipment, and monitoring and control systems can optimize the systems for the communities they serve, and save energy and water in the process.5
- Achieve on-site energy and chemical usage efficiency to minimize the life cycle environmental impacts related to the production and distribution of energy and chemicals used in the treatment and distribution process.
- Reduce chemical usage for treatment and sludge disposal by efficient process design, recycling of sludge, and recovery and reuse of chemicals.
- On-site energy generation from renewable sources such as solar and wind.18
- Effective watershed management plans to protect source water are often more cost-effective and environmentally sound than treating contaminated water. For example, NYC chose to invest between $1-1.5 billion in a watershed protection project to improve the water quality in the Catskill/Delaware watershed rather than construct a new filtration plant at a capital cost of $6-8 billion.19
- Less than 4% of U.S. freshwater comes from brackish or saltwater, though this segment is growing. Desalination technology, such as reverse osmosis membrane filtering, unlocks large resources, but more research is needed to lower costs, energy use, and environmental impacts.3
Better engineering practices:
- Plumbing fixtures to reduce water consumption, e.g., high-efficiency toilets, low-flow showerheads, and faucet aerators.20
- Water reuse and recycling, e.g., graywater systems and rain barrels.20
- Efficient landscape irrigation practices.20
Better planning and management practices:
- Pricing and retrofit programs.20
- Proper leak detection and metering.20
- Residential water audit programs and public education programs.20
Center Pivot Irrigation System21
- Dieter, C., et al. (2018) Estimated use of water in the United States in 2015. U.S. Geological Survey Circular 1441.
- U.S. Environmental Protection Agency (EPA) (2013) Fiscal Year 2011 Drinking Water and Ground Water Statistics Report.
- Electric Power Research Institute (2013) Electricity Use and Management in the Municipal Water Supply and Wastewater Industries.
- U.S. EPA (2009) 2006 Community Water System Survey.
- Congressional Research Service (2017) “Energy-Water Nexus: The Water Sector’s Energy Use.”
- Electric Power Research Institute, Inc. (2002) Water & Sustainability (Volume 4): U.S. Electricity Consumption for Water Supply & Treatment – The Next Half Century. Technical Report.
- Natural Resources Defense Council (2004) Energy Down the Drain: The Hidden Costs of California’s Water Supply.
- Tiemann, M. (2017) Safe Drinking Water Act: A Summary of the Act and Its Major Requirements. Congressional Research Service.
- U.S. EPA (2017) “Table of Regulated Drinking Water Contaminants.”
- U.S. EPA (2018) Drinking Water Infrastructure Needs Survey and Assessment – Sixth Report.
- American Water Works Association (2017) “Disinfection and Distribution.”
- U.S. EPA (2002) Community Water System Survey 2000.
- U.S. EPA (2016) Drinking Water Action Plan
- Tripathi, M. (2007) Life-Cycle Energy and Emissions for Municipal Water and Wastewater Services: Case-Studies of Treatment Plants in US.
- Abdallah, A. and D. Rosenberg (2014) Heterogeneous Residential Water and Energy Linkages and Implications for Conservation and Management. Journal of Water Resources Planning and Management, 140(3): 288-297.
- U.S. Department of Agriculture Economic Research Service (2015) “Irrigation & Water Use Background.”
- Water Research Foundation (2011) Energy Efficiency Best Practices for North American Drinking Water Utilities.
- U.S. EPA (2017) “Energy Efficiency for Water Utilities.”
- Chichilnisky, G. and G. Heal (1998) Economic returns from the biosphere. Nature, 391: 629-630.
- U.S. EPA (2012) “How to conserve water and use it efficiently.”
- Photo courtesy of U.S. Department of Agriculture, Natural Resources Conservation Service.