THE WATER-ENERGY NEXUS

In Southern California, water use is inextricably linked with energy consumption PHOTO BY RAQUEL RANCIER

Treating and distributing water in California requires 19% of the electricity used in California, and 30% of natural gas consumed in California.

I recently went to the Spring Green Fair at the Metropolitan Water District's downtown headquarters, where Southern California Edison, The Gas Company and LADWP were guest speakers in a session about energy and water conservation. It may seem confusing at first that two energy purveyors - Edison and The Gas Company - have an interest in promoting water conservation; however, upon further exploration it becomes quite evident that these two sectors are inextricably linked in Southern California. The importance of this nexus is significant since conserving one leads to conserving the other. In this age of global warming and drought, saving both energy and water are important in reducing greenhouse gas emissions as well as ensuring a reliable water supply. To further understand the energy-water nexus, it is necessary to look at how energy requires water, and how water consumes energy.

Standing at the edge of a rushing Eastern Sierra river, my attention has been drawn away from the scenic snowy vistas to the small dams operated by Southern California Edison. The powerhouse building located next to the dam greets me with the constant whirr and hum of machinery and I notice that water is being released back into the river. As I try to determine if the water is being used for cooling or hydropower, I consider that every exploration of the Sierras ultimately brings me to the water and energy connection.

The most direct use of rivers to create energy is hydroelectric power, and according to the California Energy Commission, hydro-power produces about 14.5 percent of the total energy used in California, although this amount is expected to decrease due to global warming. However, the use of water to generate electricity does not stop here; in fact all types of electricity generation require water with the exception of wind. Nuclear plants use water for cooling, coal plants use water to generate steam, and yes, even large-scale solar requires small amounts of water (although depending on their location, even small amounts can strain local water resources) to generate steam or wash mirrors. According to the Department of Energy, power generation using coal, nuclear, or natural gas is responsible for 39% of all U.S. freshwater withdrawals, which is the equivalent of about 136 billion gallons per day. While it is quite clear that water is integral to electricity production, the link to energy does not stop there: to refine one gallon of crude oil it takes about 44 gallons of water, and to produce a gallon of ethanol the amount of water needed skyrockets to 1,700 gallons. Thus, it is not a stretch to understand that reducing our energy use reduces demands on water resources. From a consumer's perspective, the connection becomes more evident by considering that, according to the E.P.A., it takes 1,500 to 3,000 gallons of water annually to power a 60-watt light bulb for 6 hours per day over the course of a year. And that's just a 60 watt light-bulb.

A journey to the Sierras also reveals the other side of the energy-water nexus; how water requires energy. Not far from the untamed rivers of the Sierras, long pipelines are strewn about the desert heading towards the single largest use of energy in the state: the Tehachapi Mountains water lift. In fact, according to the California Energy Commission treating and distributing water in California requires 19% of the electricity used in California, and 30% of natural gas consumed in California (excluding natural gas used in power plants.) When one considers the human water cycle, energy is used at almost every step. Water is pumped from its source to treatment plants, and then delivered to homes â€' all of which require energy. However, the energy use does not stop there. The water that is used in the home eventually goes down the drain and off to a wastewater treatment plant â€' again requiring energy at every step. Thus, conserving water actually reduces the energy used at each step in the human water cycle, and conserving hot water, obviously conserves even more energy. According to the E.P.A. running your kitchen faucet for 2 minutes using hot water is the equivalent energy use of leaving a 60 watt light bulb on for over five and a half hours.

The water-energy nexus has recently gained more attention at the federal level and will continue to be a hot topic as the United States, and California in particular, strive to reduce greenhouse gas emissions. In California, however, the nexus is even more important to understand, given our current drought, and the energy intensive transport of water across the state. As consumers of both water and energy, we all have the ability to make a difference by simply reducing our energy and water use.