Drought causes changes in taste and smell of tap water

Another year of drought and record-low water storage projections pushed East Bay Municipal Utility District to make two changes to its water supplies this spring, both of which will affect the taste and smell of tap water until the drought ends.

Most years, most of EBMUD’s water supply comes from snowmelt and runoff in the Mokelumne River watershed. It is stored at Pardee and Camanche Reservoirs in the Sierra. A small amount of water supply comes from the local watershed and is stored in five East Bay reservoirs. This year, Mokelumne River supplies are critically low.

Two operational changes are needed this year to manage the East Bay’s water supplies during a fourth year of drought.

First, to preserve as much cold water sitting deep in Pardee reservoir, EBMUD must switch to a higher intake valve. The cold water must be stored all summer and released downstream later in the fall, per state and federal requirements, to improve river conditions for returning salmon. Water nearer the surface of a reservoir is warmer, more sunlit and often has more algae than water deeper in the reservoir. The valve change is scheduled to take place on Sunday, May 10. Water from higher in the reservoir will start to flow to two-thirds of East Bay taps next week.

Second, last month EBMUD began filling two local reservoirs, San Pablo and Upper San Leandro, with a two-month supply of Sacramento River water purchased through a federal contract. The district is negotiating with multiple water sellers for an additional two-month supply of water also to be drawn from the Sacramento River. That water will be pumped into local reservoirs for several months. About one-third of customers have already begun receiving water from this drought supply.

Because different water sources have different water chemistry, a difference in tap water may be noticeable to customers for the duration of the drought.

“Our water this year may taste and smell different than what we are used to. It’s not ideal. But the alternatives are much worse,” said General Manager Alexander R. Coate. “We will put the Mokelumne River ecosystem at risk later this year if we don’t take water from a higher valve in Pardee. And we would have to take drastic measures like banning outdoor water use across the entire service area all summer, if we don’t draw water from the Sacramento River this year. Those alternatives are even tougher to swallow.”

To improve the taste and smell of tap water, EBMUD recommends customers chill or use a carbon filter before drinking.

All tap water EBMUD delivers to customers meets or exceeds all state and federal public health standards. The most recent annual water quality report can be viewed at www.ebmud.com/wqr.

Algae at root of changes

Algal blooms in open reservoirs are common during periods of high temperatures. A combination of different water sources, more sunshine and less rain than usual is leading to greater algal growth in water reservoirs this summer.

Algae are filtered out during water treatment but can leave behind taste and odor compounds. The most common taste and odor compounds are Geosmin and 2-Methylisoborneol (MIB).  There are no known health effects of these organic compounds, as such neither is regulated by state or federal law.

EBMUD has five water treatment plants in the East Bay. Two plants (Sobrante and Upper San Leandro) have aeration and ozonation equipment to improve the taste and smell of water. Most summers, these two plants treat water from local runoff. This year they also are treating drought supplies from the Sacramento River.

Three treatment plants (Walnut Creek, Orinda and Lafayette) have no aeration or ozonation equipment because they were built to treat Mokelumne River water that never before has required these processes.

This year staff expects the water treatment plants may not be able to fully reduce algal tastes and smells.

Planned capital improvements are in progress at some treatment plants. “But we can’t build more treatment fast enough to make a difference to the taste and smell customers will experience this year,” said Coate.

Depending on a customer’s location and sensitivity, changes may be noticed in the coming days. Some customers may notice a change in the taste and smell of their tap water when they drink it, others may notice only when the water is heated, such as in the shower. Others may not notice at all.

Residential customers with questions or concerns should contact EBMUD. Industrial and commercial customers should contact EBMUD for additional information relevant to their industrial processes. Immuno-compromised persons should consult their health care provider for advice about drinking water.