As droughts and population growth have sharpened the focus on water use, water efficiency solutions have emerged across multiple sectors and technologies. The following is an overview of some key solutions for efficient water use:

• Installing efficient appliances and devices, including low-flow plumbing fixtures, in homes and other buildings – By using less water, water-efficient appliances and devices reduce the energy required to deliver clean water, and also reduce the energy required to heat and use water on site. If just 10% of homes replaced existing fixtures with water-efficient versions, this would save 1 billion kWh of electricity per year, enough to power nearly 100,000 homes.

• Deploying water-use monitoring and customer engagement software to realize savings – Utilizing the data collected at customer meters, water utilities can engage customers and achieve an average of 5% improvement in water efficiency through voluntary actions ranging from shorter showers to reduced lawn and garden irrigation.
• Reducing reliance on water-intensive electricity generation technologies – Thermal power plants, which include coal, nuclear, and natural gas facilities, are the single largest source of withdrawals from waterways, reservoirs, and groundwater in the United States, accounting for 161 billion gallons/day in 2010, or 45% of all withdrawals. Water used by these facilities requires energy for pumping, transport, and treatment. Water use by a thermal power plant depends on the cooling system used and the efficiency of the plant, with efficient natural gas combined cycle power plants using less water than coal-fired plants. Non-thermal technologies such as wind turbines and solar PV require no water to generate electricity. As U.S. reliance on natural gas combined cycle, wind, and solar PV surged from 2005 to 2012, water use by thermal power plants dropped 36%.
• Recycling and reusing wastewater, generally on-site – Rather than discharging used water for treatment by a centralized facility such as a municipal wastewater treatment plant, wastewater can be treated and re-used on-site. This water is often called gray water, and can meet needs such as irrigation of non-food crops, industrial cooling processes, toilet flushing, and irrigation of food crops, depending on the level of treatment it receives. Recycling water cuts down on energy to transport and treat water both before and after use.
• Installing advanced irrigation systems and implementing on-site water management – At 115 billion gallons/day, irrigation is the second largest source of water withdrawals in the United States, and the largest consumer of water, accounting for 80% to 90% of consumptive water use. While investment in advanced irrigation systems is growing — up 92% from 2003 to 2008 — over half of irrigated cropland in the United States still relies on less-efficient, older irrigation systems, and only 10% of farms use advanced water management tools. Pumping irrigation water accounted for $2.7 billion in on-farm spending in the United States in 2012, and reducing the amount of water pumped would cut back on these costs.
• Using rainwater collection systems – Rainwater harvesting (RWH) involves capturing, diverting, storing, treating, and distributing rainwater for use. RWH can be used to meet a variety of water needs, including in-home use, landscaping, livestock, and fire protection.
• Investing in infrastructure improvements and repairs – On average, water treatment and distribution systems lose 14% of water through leaks — in some systems this gure is as high as 60%.18 By conducting a water audit, utilizing leak detection equipment, repairing leaks, and implementing effective operations and maintenance programs, municipalities can minimize these losses and reduce energy use for treating and transporting water that is lost along the way.

Water utilities, businesses, farmers, and consumers across the country are already taking advantage of these solutions. After increasing steadily from mid-century (when the United States Geological Survey began tracking water use), total water use has remained relatively constant since 1985, and from 2005 to 2010 dropped 13% to reach pre-1970 levels. These water savings translate to energy and cost savings. The small town of Gallitzin, Pennsylvania, saved a total of $25,000 annually — a 60% reduction in energy costs and a 50% drop in chemical costs — when it reduced water use by 60% over the course of four years through leak detection alone. In Massachusetts, a more comprehensive conservation program including not only leak detection but also home retrofits, water management programs, improved metering infrastructure,
and updated plumbing codes, resulted in estimated savings of $111 million to $153 million at upfront costs of $20 million. The savings came from deferred investments in water supply and treatment infrastructure. Despite progress in some municipalities, there is still potential for dramatic improvement across the country.

Data and management technologies used to reduce energy use, such as advanced metering infrastructure, are also increasingly used to control and reduce water use. For example, using AMI in conjunction with WaterSmart Software, a data analytics platform for water utilities, Park City Water in Utah is now able to provide real-time leak alerts to customers; in three months, the utility delivered over 150 alerts, and 70% were resolved within 10 days. Using the same software, the city of Greeley, Colorado, was able to reduce water use by 4% during a time of drought through voluntary actions alone. The Pacific Institute estimates that cost-effective measures can reduce urban water use by 30% in California. Applying these savings across the country would result in nearly 54,000 million kWh saved, representing over $5 billion in cost savings and enough electricity to power nearly 5 million homes. Reducing agricultural, industrial, and power sector water use would deliver even higher energy savings. In addition to reducing water use, reusing water also delivers huge savings. Under a public-private partnership with Veolia Water, Oklahoma City has saved residents over $150 million since 1985 through a water reuse program. At the same time, the program saves money for large water users including two local electric utilities by supplying them with reuse water, which is 33% cheaper than drinking water.