Water and Energy Nexus

Water and energy in California, as well as in many other parts of the world, are inextricably intertwined. While water starts so simply as precipitation, water serves many different purposes as it moves through California. To move water through California, large amounts of energy are used and generated. In fact water moved throughout the California State Water Project (SWP) generates an average of 4.5 billion kWh annually. Much of this energy is generated through power and power recovery plants located at many of the State Water Projects reservoirs and along the California Aqueduct. To move water throughout the state, power requirements have ranged from more than 8 billion kilowatt hours a year, as in 1990, to under 4 billion kWh, as in 1995. Therefore the SWP must pay to import energy generated elsewhere in order to meet water delivery obligations.

In terms of overall energy use, water-related energy consumption in the state represents approximately 15%-20% of all energy consumed in California. This enormous amount of energy is required to allow farmers to irrigate their fields, the general public to have clean water to drink and bathe in, and to keep every garden green and healthy. Reducing overall water consumption through water efficiency measures, reusing water, drawing on alternative sources such as rainwater and graywater, irrigating agricultural crops efficiently, growing native and non-native low-water using plants in the place of high-water using landscapes such as turf grass, not only will reduce the amount of water used, but require less generated energy to move this water to its end use.

Many people in California may believe that once they use water and send it down the drain there is no more associated energy use, since gravity takes it out of the home or workplace. Much of the wastewater from sinks, showers, and toilets located in urban areas throughout the United States travels through sewer systems that feed water pollution control plants. Unfortunately, all of this wastewater must be treated to a legal standard of cleanliness prior to being released back to the environment. This process is generally very energy intensive. Electricity constitutes between 25 and 40 percent of the budget of a typical wastewater treatment plant. It can be assumed that through the further use of water conservation techniques such as installing High Efficiency Toilets (HETs), low-water using showerheads, sink aerators, as well as rainwater and graywater systems, less wastewater will be generated and therefore less energy will be needed.

Water and energy will continue to be intertwined as long as our society grows crops in areas that do not have adequate local water sources, live in arid and semi-arid regions, grow ornamental high-water using plants, and use inefficient indoor water fixtures. There are solutions that will reduce our reliance on energy dependant water resources, but it takes a societal change to become more aware of our resource usage and to understand that all resources are linked in many complex ways.

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