Clean drinking water has never been in short supply in the Spokane area. As the region grows in the coming decades, however, that may change.

Water demand in the metro area is expected to increase 37 percent between 2010 and 2040, according to a Spokane County forecast from last year.

The source of all that water – the immense Spokane Valley-Rathdrum Prairie Aquifer – is looking ever smaller. Smaller to public water providers confronting limits on how much more they’ll be able to draw from underground, and smaller to Spokane River advocates sounding the alarm over low summer flows.

Unlike so many sources of groundwater across the West, the aquifer beneath the valley floor holds up well to pumping for public and private supplies. It’s a resilient system underground.

But near the surface, where the aquifer and the Spokane River mingle, pumping from the aquifer draws down the river in summer to the detriment of fish and wildlife, a 2007 Washington-Idaho aquifer study confirmed.

Declining river flows led Washington in the early 1990s to stop issuing new water rights for public water systems on the aquifer, leaving cities and water districts to operate under existing water rights. Water managers wonder how they’ll meet the demands of growth without expanding their claims on the aquifer.

“That’s the question we ask every day. We don’t know,” said Ty Wick, general manager of Spokane County Water District 3.

District 3 has had water right applications submitted to the state since the early 1990s, and the Department of Ecology won’t process them, said Wick, who also is president of the Spokane Aquifer Joint Board.

“I call it the paper drought,” he said.

Ecology officials are working now to establish a water right for the Spokane River to ensure the summer flow is adequate for fish habitat, water quality and other values. The goal, the state says, is to protect the river from future withdrawals, not cut into existing water rights.

“It’s not like we can go out and enforce it by busting a bunch of guys or canceling water rights,” said Guy Gregory, senior hydrologist at the Department of Ecology. “But it will provide the public with an idea of what a healthy river flow looks like, and we think that’s probably the best way we have available to encourage sensible water development in the region.”

Once a minimum stream flow is set for the Spokane River, any new water rights granted from the aquifer would be junior to it, meaning those new withdrawals could be curtailed if the river drops too low, Gregory said.

The moratorium on new water rights and potential for future restrictions on withdrawals could have unintended consequences, said Susan McGeorge, manager of Whitworth Water District 2. If new developments can’t connect to public water supplies, they will drill private wells to tap the aquifer, which undermines the state’s effort to curb draws on the aquifer, McGeorge said.

Some providers already are running out of water. The East Spokane Water District, for one, has exceeded its water right and now buys aquifer water from Modern Electric Water Co. That water is sent across the Valley through another water district’s pipes to East Spokane customers.

“It’s kind of a world of haves and have-nots out there in the Spokane public water supply community,” said Rachael Paschal Osborn, senior policy adviser for the Center for Environmental Law and Policy.

The city of Spokane is one that has a lot of water to spare under its existing water rights. The city already delivers water to neighborhoods outside city limits and pumps water out to Airway Heights on the West Plains, where water is scarce.

Likewise, most of the larger public water systems in the county have yet to tap all the water they’re guaranteed. According to Ecology, the purveyors collectively can take another 210 cubic feet per second of water – about 136 million gallons a day – out of the aquifer under current allocations. And less than a quarter of that volume will be needed to meet projected demands over the next 30 to 40 years, Gregory said.

“They have ample water to serve any customer that comes to them,” he said.

The downside is the low summer flow in the river will drop further as existing water rights are fulfilled, and the state can’t stop that.

“Substantial quantities of water already are allocated and being used,” Osborn said. “The problem with low flows in the Spokane River, that’s a present-day situation.”

One obvious way purveyors can prolong their water rights is by promoting smarter water use, Gregory said.

“The cheapest, most available source of new systems is conservation. Just is,” he said. “It saves money, it saves energy, it saves water.”