Posted on February 12, 2014

In a Dry Year, PG&E Strategically Manages Water to Optimize Hydropower and Supplies for Users

By Paul Moreno and Lynsey Paulo

High in the Sierra Nevada, a PG&E hydro operator cranks a wheel to completely shut off a gate on a dam. Although the electric-powered gate can be closed to less than 2 percent with a switch, hand-turning the wheel stops the tiny flow completely.

With a record drought in progress, each drop of water counts.

The mountains around the Spaulding Reservoir have less snow this year. Each winter, PG&E draws down the reservoir to about the level seen here to make room for rain and snow run off. But with less rain and snow this year filling up the lake, PG&E is saving as much water as it can. (Photos by Paul Moreno.)

Even as much-needed and very-welcomed rain fell on Northern and Central California last week, the drought remains a reality. That’s why PG&E crews are working hard to save water in reservoirs rather than release water to generate hydropower now. Saving the water means the utility will be able to use low-cost, clean hydropower to generate energy for customers this summer, and for farming irrigation and drinking water needs.

“We are strategically generating less hydropower now so that we can save water in our reservoirs for generating power during the summer peak periods, when demand for power is higher,” said Debbie Powell, PG&E’s director of hydroelectric operations and maintenance. “Hydropower also enables us to better integrate wind and solar generation to the grid. We are managing our reservoirs with the aim of filling them as much as possible before the start of summer.”

Governor declares State of Emergency

The record drought has hit California’s water supply extremely hard, prompting Gov. Brown to declare a State of Emergency on January 17 and to call on Californians to voluntarily reduce their water usage by 20 percent.

According to state water officials, California’s rivers and reservoirs are below their record lows and the snowpack’s statewide water content is about 27 percent of normal average for this time of year, even with the recent storms.

PG&E’s Wise Powerhouse near Auburn was generating only one megawatt of power in early February, rather than the usual 12 MW. The lower-than-normal flow of water is going to a local water agency so PG&E harnesses that power.

Despite record drought conditions, PG&E’s 17 largest reservoirs are currently above 90 percent of normal storage levels for this time of year when reservoirs are typically maintained at lower levels to make room for spring and summer runoff from the Sierra snowpack. However this year, levels at many smaller reservoirs are lower due to the lack of rain, not because PG&E has been releasing water to make room for rain and spring snowmelt.

The utility is working with regulatory agencies and water users to reduce the required releases from its reservoirs in order to lessen the drought’s impact on the environment, as well as prolonging the availability of water for farming and residential needs.  Saving water for later generation is compatible with delayed release of water for environmental and consumptive perspectives.

Can’t predict winter rain, summer heat

As with the rest of California, how much water is available to PG&E depends on the weather. The rainy season is only about half way over, so just how much less hydropower PG&E will have and the cost of replacement power depend on how much snow and rain falls for the remainder of the season, as well as actual weather conditions this summer.

Although it’s too early in the season to predict if there will be additional costs to purchase power to replace hydro generation or how customer rates and electric bills might be affected, it’s good to remember that electric generation is only a portion of the overall electric rate, and hydrogenation is a relatively small portion of PG&E’s overall power mix.

Replacement power will be impacted by a number of factors including the amount of power generated from solar and wind resources, temperatures and lengths of any summer heat waves, and how well customers conserve energy through the summer months.

(Click here to read about what PG&E is doing related to the drought.)

Email Currents at currents@pge.com.

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