Municipal water in Harbor has turned brackish again, prompting Harbor Water District officials to offer free, potable water to its customers for at least the next week, Superintendent Herman Bloemsma said Monday.

The water district offices are at 98069 W. Benham Lane.

Salinity levels at the community’s Raney collector system dipped to 1,200 microsiemens (ms) Tuesday — after a weekly high of 1,500 ms Monday — and up from 500 ms two weeks ago.

Anything above 800 ms is considered brackish, Bloemsma said.

“It’s just low flows and high tides,” he said. “Once that ocean water hits that little plain (in the Chetco River where the intake valve is situated), it’s heavier than regular water and sinks, and that’s where we’re sucking from.”

Water started going salty about two weeks ago, he said, but a rainstorm shortly thereafter flushed the salt out. Since then, warm weather and a lack of rain have contributed to the lower water levels in the Chetco River, from which Brookings and Harbor draw their municipal water.

Harbor’s intake valve is 2.5 miles upstream on the Chetco River; Brookings’s is 2.8 miles farther upstream and has never had to address salty water.

The water gets brackish when low water levels in the Chetco River coincides with higher-than-normal tides. The low water volume in the riverbed then allows saltwater to flow upstream from the ocean. Full moons can also exacerbate the situation.

Low water levels don’t presage a shortage of the resource, either, officials have said in the past, noting that the city and Harbor barely make a dent in the amount they collectively take from the river.

The tides aren’t unusually high right now, Bloemsma said. But the water level in the Chetco River is flowing at 77 cubic feet per second, as measured by a U.S. Geological Survey gauge farther upriver. The median flow in the river for this time of year is 114 cubic feet per second, according to the USGS.

Last year at this time, the river was flowing at 7,280 after a torrential rainstorm.

“Earlier in October, we had a big rain and so it wasn’t an issue,” Bloemsma said of salinity levels that rose to 500 ms then dipped to 80 ms. “Now we’re looking at another week of sunshine. We’re probably going to have that water truck for about a week.”

For the past four or five years, water has begun turned brackish in August and Harbor residents had to rely on trucked-in or store-bought water to get them through until the next rain storm.

Harbor Water District’s collection system has six “fingers” that collect the water from an aquifer beneath the riverbed. A computer system lets Bloemsma determine which fingers are withdrawing the best water.

He has shut off four of the six this week.

The situation has become desperate in some years; in 2014, an unusual high tide coincided with drought conditions and a full moon, bringing salinity levels to 2,800 ms, according to Pilot reports.

People with certain medical conditions can’t consume that salty water. Pets turn their noses up at it. Plants wither and die.

One year, some people took to stealing water from city residents, even though a vast majority of Brookings residents offered to open their spigots to them for free. People complained about having to buy water — arguing that they already pay the water district — and stockers at local stores were hard-pressed to keep the shelves full.

Ideas to fix the problem run the gamut, but none have been deemed feasible, so far.

A gravel bar that blocks the ocean tides from getting into the subterranean pool from which Harbor’s water could be removed, but would require U.S. Army Corps of Engineer approval.

Harbor could relocate its Raney collection system, but all the water farther upstream is spoken for.

The district has even pondered the idea of a desalination plant, but its multi-million-dollar expense is unrealistic, too.

In 2015, the governor declared the situation a disaster, opening up fiscal coffers for aid to solve the problem, but people in Harbor needed water immediately.

The city of Brookings, too, has offered to create an “inter-tie” to help make Harbor’s water system more secure by providing water to it in dry times, but the water district has not expressed interest, said former City Manager Gary Milliman.

Salty water was also among the factors the city sought federal funds to build a 500,000-gallon water tank near the Brookings Airport. That water can also be used for future growth in the north end of the city, airport needs and to fight wildfire.