Drinking Water on an Island
Over the past few weeks, we’ve taken a look at water in the challenging environment of the desert. Desert communities in the American Southwest are able to bring water hundreds of miles from the Colorado River. Over the next few weeks, we’ll be taking a closer look at water in another challenging environment, islands, though the lens of my home of Whidbey Island in Puget Sound. This post is a little more technical than usual, but I think worth your while.
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Like Coleridge’s Ancyent Marinere, islands are surrounded by water, but water to drink can be scarce. In most cases, there’s no way to pipe it in, so an island must be self-sufficient. Mostly Water has island-dwelling subscribers and followers from Hawaii to Orkney, from Martha’s Vineyard to Malta, and many on the islands of the Pacific Northwest’s Salish Sea. The more northerly of these local islands, including British Columbia’s Gulf Islands and Washington’s San Juans, are rain-shadowed and made of rock. Water is scarce here, and residents use desalination, rainwater collection, and reclamation to get by.
The more southerly islands, those in Puget Sound, are composed of a mixture of sand, gravel, and clay known as glacial till, left over from ice age glaciation, which can support an aquifer, and mostly have a little more rainfall. Fresh water exists on these islands in dynamic equilibrium with the saltwater around and under the islands. The unconsolidated layer containing the aquifer is between hundreds and several thousand feet deep, and at depth is saturated with salt water.
Some of these islands are too narrow for the aquifer to remain free of seawater intrusion. Marrowstone Island, one example, is close enough to the mainland to pipe in drinking water. Another, Gedney Island, colloquially known as Hat Island, has had to install a desalination plant.
Whidbey Island straddles the north and south parts of the Salish Sea. The northern end is rockier and is close enough to the mainland to pipe water from the Skagit River over the Deception Pass Bridge to the north end, including Naval Air Station Whidbey and the City of Oak Harbor. Although the Skagit River is close, the rest of the island doesn’t get to use its water, as withdrawals are restricted to maintain instream flow for salmon. We get to use our sand and gravel aquifer.
I’m talking to three local groups this month about their concerns around water availability on the island. In the first of these, the County Commissioner representing the southern part of the island asked me to talk to a group of concerned constituents about water availability for the projected population growth. That conversation took place on Monday last week. I was expecting about a dozen people, but forty showed up. It was very encouraging to see so many concerned about water! The crowd was diverse, with representatives from the farming community, local housing and environmental non-profits, county staff, and the general public. The local paper was there too! Water quality and supply a concern on Whidbey Island | South Whidbey Record. Here are some of the topics we discussed.
Do we have enough water?
The growth projections are for another 15,000 residents on top of the current 80,000 in Island County. Many of those would be in the southern part of Whidbey Island served by groundwater. There was a good deal of discussion about how much of water is in the aquifer. That’s both hard to measure and of limited value, as our aquifer is more like a leaky bathtub than a tank. The name of the game is to make sure that the amount we pump out of the aquifer doesn’t exceed the amount that’s recharged from rainfall.
Aquifer recharge
All our groundwater comes from rainfall, but not all our rainfall becomes groundwater.
Runoff in our case is augmented by interflow and seepage — groundwater exiting into salt water around and below the aquifer — a flow that is needed to keep the salt water at bay. The amount of recharge depends on rainfall, geology, soil type, and ground cover.
All of these factors, and therefore recharge, vary greatly over the island. Each drainage basin is different. Some are able to handle higher densities and different types of development that others. Here’s the resulting distribution of recharge rates.
All these recharge figures are from Estimating Ground-Water Recharge from Precipitation on Whidbey and Camano Islands, Island County, Washington, Water Years 1998 and 1999. Whidbey Island is the larger island on the left. The two islands together comprise Island County.
Forested land has the highest recharge rate, but current rules require periodic timber harvests to qualify for a forestry tax break, leading to a proliferation of clear cuts and a degradation of recharge. Non-profit groups are pushing the idea of a credit here that recognizes the critical role forests play in maintaining our aquifer.
The predominant development pattern on the island is a single-family home on a wooded five-acre parcel. Everyone wants a cabin in the woods! Developing these parcels involves cutting down some trees, building a driveway, a house, an outbuilding or two, a patio, apron, lawn, private well, and septic system. None of these changes is good for recharge! Low impact development standards with retention ponds and rain gardens do not (yet) apply in these areas. It’s not unusual to see runoff flowing down the driveway into the county roadside drainage ditch and ultimately into the sound. Development will need to be more concentrated in areas served by community water systems and sewers.
The Safe Drinking Water Act, fifty years old this year, excluded from most regulation private wells and small water systems serving less than fifteen connections. The State Department of Ecology doubled down by making wells for up to six connections permit exempt, meaning they don’t need to apply for a water right. The unintended, or perhaps not so unintended, consequence was to incentivize this type of development over larger community water systems. The county now has almost 9,000 wells for the maybe 60,000 people who are on groundwater. That’s a well for every seven people! There’s also a cow for every seven people in the state, but that’s a different story. The infrastructure to service and maintain all these wells has already been stretched beyond breaking point.
Availability
Usability of the aquifer is constrained in some areas by contamination. The most widespread of these is sea water intrusion. Wells near the shoreline are at risk of pulling sea water into the well, known as upconing. Increased pumping and sea level rise are increasing the risk.
Septic systems and animal feedlots have increased nitrate and related contamination in some areas. A newer contaminant of concern is PFAS, “Forever Chemicals”, predominantly from firefighting foam. As compulsory testing of larger water systems rolls out over the next two years, the full extent of this contamination will become clear, and will put areas of the aquifer off limits. You can read previous posts on PFAS here, with more posts on this issue in the coming year.
Unfortunately, just as the Safe Drinking Water Act doesn’t protect private wells, the Clean Water Act doesn’t protect groundwater, leaving county code as the only tool, one that was not designed for the job.
Consumption
This conversation around development initially focused on water consumption. As it turns out, domestic water use accounts for a small percentage of consumption. The threat to water supply through development’s impact on recharge, as detailed above, is actually greater. There is one big exception. Lawns. Lawns impact both.
Lawns use large, insanely large, amounts of water. One residence I’m aware of put eight feet of water on the lawn one summer. That lawn was the wettest place in the lower forty-eight state, beating out the Olympic Peninsula’s Hoh rainforest. Worse, it’s on the beach, so that water went straight into the sand, and then the Sound.
Lawns came from England, where it rains in the summer. Pacific Northwest summers are dry (don’t tell anyone, please). Summer domestic water use driven by lawn irrigation is three times higher than winter. That increases the maximum daily usage, and therefore the cost, of supplying water from a community system. Lawn water is lost to evapotranspiration and runoff and doesn’t go back into the aquifer. Community water systems, like mine, can at least increase consumption rates for high volume users until we’re accused of class warfare. It doesn’t reduce the consumption, but at least it builds our financial reserves!
The other major user of groundwater here is agriculture. I’ll be presenting to a couple of farming groups over the next couple of weeks. I’ll be back with a post on that.
Solutions
Potential solutions, then, include putting constraints on the type and location of development, discouraging lawns, and proactively protecting the aquifer, all a heavy lift for a county planning process.
Putting the private well and small water system toothpaste back in the tube through water system consolidation is every bit as hard as I just made it sound. I’m involved in one such effort, and will be reporting on that too in due course.
I’m encouraged by the number of people who are concerned about water, on this island and around the world.
Thanks as always for listening or reading. Whether you’re on an island or not, I want to hear about drinking water where you live. Let me know in the comments. To make sure that you receive the latest posts on water, please consider becoming a subscriber.
