The Honolulu Board of Water Supply is asking Oahu water customers to reduce their water usage by 10% amid fears of shortages after well closures due to the Navy’s fuel contamination crisis. 

Late last year, BWS closed the Halawa Shaft, which supplied 20% of urban Honolulu’s water, and two additional wells as a precaution after the utility learned that fuel from the Red Hill facility that serviced the Pearl Harbor area had tainted the military’s drinking water. BWS now relies on fewer wells to serve the 400,000 people who live between Moanalua and Hawaii Kai, and if they are overpumped, they will become too salty to drink.

The Beretania pump station already has experienced a major spike in chlorides, an indication of saltiness. 

“We had hoped we could avoid this,” BWS Chief Engineer Ernie Lau said in a statement. “Unfortunately, we are in a difficult situation not of our own making.”

The island –  particularly the area including Waimalu, Aiea and Halawa – needs to cut back its demand before the aquifer runs out of supply, Lau said Thursday at a press conference.

Future disruptions are likely. Water shortages, particularly in the drier summer months, could mean lower water pressure or even mandatory water shut-offs, Lau said. 

“Customers may not have water for periods of time,” he said. 

Some 93,000 Navy water customers were immediately impacted by the contamination crisis last November. Thursday’s announcement marks the first major impact to BWS customers due to the contamination. 

Adding to the challenge is less frequent rainfall, BWS officials said.

The aquifer gets recharged by rainwater seeping through the ground, but because of climate change, weather has become increasingly extreme – either intense droughts or intense floods, said Barry Usagawa, the program administrator for the BWS Water Resources Division. 

During a flood, like that caused by the heavy rains Oahu experienced in January, much of the water just runs into the ocean instead of getting absorbed into the aquifer, Usagawa told reporters.

Despite those climate impacts, Lau said that if the Halawa shaft was open, water conservation advisories wouldn’t be necessary.

BWS is preparing letters about the 10% reduction advisory to Honolulu’s 200 top water users, which include government agencies. The utility hasn’t identified those users, but BWS is in talks with tourism industry leaders, like the Hawaii Lodging and Tourism Association and the Waikiki Improvement Association, to get them on board, BWS spokeswoman Kathleen Elliott-Pahinui said. 

In response to the BWS advisory, the City and County of Honolulu will immediately change its practices around the watering of municipal golf courses, city spokeswoman Brandi Higa said in an email. The Ala Wai, Pali and Kahuku golf courses will reduce water frequency and duration and only irrigate the priority areas on the golf course, such as putting greens and tees.

At the Ala Wai Golf Course, the irrigation water is predominantly brackish well water mixed with potable water from BWS. Going forward, the course will change the ratio of brackish to potable water to reduce its BWS water usage, Higa said.

“We appreciate the work of the Board of Water Supply and continue to coordinate with them closely to ensure (best management practices) are achieved,” she added.

Suggested ways to reduce usage include taking shorter showers, watering lawns less frequently and doing it before 9 a.m. or after 5 p.m., checking for leaks in plumbing and toilets and installing water-efficient plumbing fixtures, BWS said.

BWS also offers rebates to residences and businesses that invest in water-efficient appliances, plumbing and landscaping.

The scope of the Navy’s contamination, and what direction it may be traveling, is being studied but is still unclear, so BWS will keep the Halawa-area wells closed for now, Lau said. BWS is on the hunt for locations to drill new wells, but setting one up can take years, he said.

According to Lau, it’s unlikely that the agency will find another spot in Oahu’s urbanized environment that is as plentiful as the Halawa shaft, which was built in the 1940s.