Down the Drain
California has been through its share of scorching droughts and energy shortages, but many residents of the western United States may not realize the close connections between water and power resources. Water utilities use large amounts of energy to treat and deliver water. Even after utilities deliver water, consumers burn more energy to heat, cool, and use the water.
Despite these connections, water planners at the federal, state, and local levels have largely failed to consider the energy implications of their decisions. Water agencies select water sources without assessing the energy costs of transporting the water over great distances to its users. Likewise, they fail to consider the energy savings of using less water. This kind of disregard for the energy implications of water leads to high costs for consumers and wasteful water-supply decisions.
A proper understanding of water and energy, however, can save both money and resources. Our report presents a model for how policymakers can calculate the amount of energy consumed in water use. We applied this model to three case studies in the western United States, and our analysis shows that integrating energy use into water planning can save money, reduce waste, protect our environment, and strengthen our economy. Water planners can use this model in their own regions to find similar solutions that will benefit consumers and the environment alike.
We quantitatively evaluated the connections between energy and water in three case studies. We used San Diego County's search for future water supply options to highlight energy use in urban water systems. Our examinations of the Westlands Water District and the Columbia River Basin illustrate energy use in agricultural settings. Our research found the following.
Water conservation lowers energy use and energy bills. The San Diego case study revealed that end use of water -- especially energy intensive uses like washing clothes and taking showers -- consumes more energy that any other part of the urban water conveyance and treatment cycle. This is a rather striking finding since conveyance is a much more obvious energy consumer, particularly in Southern California. Therefore, reducing water use can save significant amounts of energy. For instance, if San Diego relied on conservation instead of additional water from Northern California to provide the next 100,000 acre-feet of water, it would save enough energy to provide electricity for 25 percent of all of the households in San Diego.
Water recycling is a highly energy efficient water source. In both urban and agricultural settings, reusing water is far less energy intensive than any physical source of water other than local surface water. For example, Orange County is constructing a water recycling system that will use only half the amount of energy required to import the same amount of water from Northern California. Even groundwater pumping is more energy intensive in San Diego and the Westlands Water District than water recycling from urban wastewater; and the depth to groundwater in these locations is not atypical for western settings.
Retiring agricultural land may increase energy use if the water is transferred to other agricultural or urban uses. Transferring water from retired, drainage-impaired Westlands land to urban settings would dramatically increase energy use because urban water use is typically more energy intensive. For example, we estimate that transferring the conserved water to San Diego would require an additional 1.3 billion kWh/yr compared to leaving that water in the delta. Allowing water to remain in Westlands would likely result in an increase in permanent crops and a significant increase in embedded energy ranging from 16 percent to 48 percent depending on assumptions.
Retiring agricultural land can save energy if the water is dedicated to the environment. Using data from the Westlands Water District -- one of the largest agricultural users of water in the West -- we concluded that ending irrigation to retired farmlands could generate large energy savings if the water remains instream. Retiring 100,000 acres of drainage-impaired farmland in Westlands, with corresponding reductions in Central Valley Project deliveries, could save at least 71 million kWh from reduced Central Valley Project pumping. This is enough to meet the residential energy needs for the city of Modesto for two months. Retiring this land could also save an additional 50 million equivalent kilowatt-hours used for cultivation and harvest.
Diverting water above dams costs power and money. Our Columbia case study demonstrates that when water is diverted for irrigation before it reaches a dam, an enormous amount of energy -- the foregone energy production -- is lost. For example, the foregone energy production in the Columbia Basin Project is the equivalent of 30 percent of the total energy use for the city of Seattle. This loss may be large enough, in dry years, to make it possible to pay farmers more than they could earn growing low-value crops and still have enough money to purchase environmental flows when they are most valuable.
All three of our case studies demonstrate that including energy considerations in water management decisions can lead to significant energy -- and money -- savings. The case study analysis supports two primary recommendations for how policy makers can begin to achieve these savings.
Decision makers should better integrate energy issues into water policy decision making. Looking at energy use and water use simultaneously generates valuable insights that do not arise from separate policy analyses of water and energy issues. We therefore recommend:
Both water and energy policymakers should give water conservation higher priority. Surprisingly, policy actions that affect end uses of water may have much larger energy implications than policy actions that affect the mix of physical water sources. We conclude that conservation has much greater potential, and stronger energy-related economic and environmental benefits, than has been recognized to date. In addition, the energy benefits of conservation can generate air quality and climate change benefits. Given this strong finding, we recommend: