Summer water | Part 2 of 5

This article is the second of a five part journalism series by the San Juan Islands Conservation District on streams and wetlands in the islands, and what people can do to restore them

||| FROM SAN JUAN ISLAND CONSERVATION DISTRICT |||

By August, the islands begin revealing what kind of year it has been for water.

The clues emerge quietly at first. Gravel bars widen beneath shrinking channels. Alder roots become exposed where winter flows cut deeper into simplified streambanks. Springs dry. The changes rarely arrive dramatically in the San Juan Islands. Freshwater decline here does not often resemble catastrophe in the Western sense—there are no empty reservoirs or collapsing river corridors. Instead, the crisis unfolds through accumulation: warmer summers, diminished
groundwater, fragmented wetlands, simplified stream channels, and the gradual unraveling of hydrologic systems that once buffered the islands against drought.

In State of Knowledge: Climate Change in Puget Sound (University of Washington Climate Impacts Group, 2015), researchers projected that Washington State would continue experiencing warmer average temperatures, reduced summer streamflows, earlier snowmelt, and more frequent summer drought conditions. Average annual temperatures in Washington have already increased by roughly 1.5°F since 1920, with the strongest warming occurring during summer months and nighttime minimum temperatures.

More recent assessments suggest those trajectories are accelerating. In the Fifth National Climate Assessment published by the U.S. Global Change Research Program in 2023, scientists projected that the Pacific Northwest will continue experiencing increasing winter precipitation extremes, declining summer water availability, longer wildfire seasons, and more frequent marine and freshwater heat events throughout the twenty-first century.

For islands dependent almost entirely upon winter rainfall recharge rather than snow-fed river systems, those projections carry particular weight.

A 2021 report from the Washington State Department of Ecology further warned that many groundwater-dependent watersheds throughout western Washington may face increasing summer water stress as warming temperatures alter recharge timing, reduce soil moisture retention, and intensify evapotranspiration during drought years. For salmon-bearing streams, those changes are profound.

The Washington Department of Fish and Wildlife notes that juvenile coho salmon and coastal cutthroat trout are highly sensitive to elevated stream temperatures, particularly during late summer low-flow conditions. Studies throughout western Washington have shown that riparian shade can reduce stream temperatures by several degrees Celsius—often enough to determine whether fish survive prolonged heat events.

Along streams like Crow Valley Creek and Garrison Creek, these thresholds are no longer theoretical.

Without wetlands, rainfall rushes rapidly toward the ocean during winter storms instead of infiltrating deeply into soils. Without trees, streams absorb direct solar radiation throughout increasingly hot summers. Without large woody debris, channels lose the roughness and complexity needed to create pools, reconnect floodplains, and retain moisture in surrounding soils.

Hydrologists sometimes describe this phenomenon as “flashiness.” In River Ecology and Management: Lessons from the Pacific Coastal Ecoregion (Naiman et al., 1992), researchers describe how simplified stream systems tend to experience larger winter surges and sharper summer declines because water is exported rapidly from watersheds rather than stored across floodplains, wetlands, and groundwater systems. Many island streams today are, in effect, over-efficient. What once functioned as slow hydrologic systems now behave more like drainage infrastructure.

The disappearance of wood is especially striking. Historical stream surveys throughout the Pacific Northwest consistently describe channels filled with fallen cedar, Douglas-fir, rootwads, and logjams. In Wood in World Rivers (Gregory, Boyer & Gurnell, 2003), researchers concluded that large woody debris plays a foundational role in pool formation, sediment storage, nutrient retention, and fish habitat complexity.

Yet throughout much of the twentieth century, streams were systematically “cleaned” of wood under the assumption that simplified channels were healthier and less flood-prone. The result is a landscape where water moves faster but ecosystems function less effectively.

And climate change is intensifying the imbalance. According to projections from the University of Washington Climate Impacts Group, western Washington is expected to experience wetter winters with more intense storm events alongside hotter, drier summers and reduced groundwater recharge reliability.

The islands are becoming simultaneously wetter and thirstier.

And the future of island water may depend increasingly on groundwater hidden beneath glacial soils and fractured bedrock. The San Juan Islands rely heavily upon seasonal rainfall recharge rather than large snow-fed river systems. In drought years, shallow aquifers and wetlands effectively become biological savings accounts carrying winter rain into late summer.

Perhaps that is what makes freshwater decline in the islands feel so emotionally complicated. The losses are not complete enough to feel hopeless. But neither are they distant enough to ignore.

This project is supported with funding from Washington’s Climate Commitment Act. The CCA puts cap-and-invest dollars to work reducing climate pollution, creating jobs, and improving public health. Information about the CCA is available at www.climate.wa.gov.

SEE ALSO:

theorcasonian.com/the-creeks-beneath-the-fields-part-1-of-5/PART 1