A Drying, Shrinking Lake

A myriad of factors have reduced water flow into the lake, increasing its salinity or drying up the lake altogether. Important aspects of water use in the Chewaucan Basin remain unmeasured, water rights have been over-appropriated, and a poorly regulated reservoir at the bottom of the watershed has reduced flows from the Chewaucan River — Lake Abert’s primary water source — to the lake for decades.

As a terminal lake fed primarily by the Chewaucan River, water levels and salinity in Lake Abert are dependent on a balance between fresh water flowing into the lake and evaporation. However, a myriad of factors has upset that balance so that not enough water is arriving to the lake.

Water management in Oregon is based on the Doctrine of Prior Appropriation. Water rights are allocated on a “first in time, first in right” basis, meaning the earlier in time an individual first secured a water right (priority date), the more senior their water right. In years where there is not enough water available for all water right holders, senior rights are fulfilled first, resulting in decreased quantities available to those with junior rights. Junior users and those without water rights — such as Lake Abert — are sometimes left with no water at all when all available water is diverted by those with senior water rights. This means the water has been “over-appropriated.”

Water rights for surface and ground water are allocated, permitted, and regulated by the Oregon Water Resources Department (OWRD). State agencies may apply for water rights for rivers and water bodies to keep water instream for fish, wildlife, recreation or other “beneficial uses.” However, senior water rights with an earlier priority date receive their full water allocation before junior instream water rights are fulfilled. Lake Abert has no water rights.

There is only one stream gage in the Chewaucan River, located near Paisley approximately 23 miles upstream from Lake Abert. OWRD does not require water use to be measured and reported, meaning there is no clear record of actual water use in the basin. A 1971 study estimated that approximately half of the water in the Chewaucan River between 1924-1964 did not make it to Lake Abert. An in-depth analysis of Lake Abert’s drying in 2014 concluded that the drying was driven by upstream water withdrawals. An in-depth analysis of Lake Abert’s drying in 2014 published by University of Montana geoscientist Johnnie Moore concluded “Without upstream withdrawals, the Lake Abert ecosystem would have been stressed in recent droughts, but not decimated as it has been in the last two years.” Demand for new out of stream uses has only grown over time even while drought and climate change has reduced overall water availability.

A reservoir constructed at bottom end of the Chewaucan River in the early 1990s limits how much water is able to reach to Lake Abert. In its initial permitting, the Oregon Department of Environmental Quality (DEQ) required the reservoir constantly release water to the lake if the lake water level dropped below an elevation of 4,252 feet. The Oregon Department of Fish and Wildlife (ODFW) also recommended operation of the reservoir be reevaluated if Lake Abert went dry or every five years, and OWRD determined a permit would only be approved with pass-through flow conditions incorporated. However, these requirements and the operating permits were abandoned along with agency oversight when construction uncovered important Native American graves and archaeological resources. Without this oversight or management, water makes it through the reservoir and to Lake Abert only when it overflows or is voluntarily released. The water right permits for this reservoir remain disputed and unresolved today, more than 30 years after construction began.

Although endorheic lakes naturally fluctuate in size due to inter-annual variations in precipitation, Lake Abert has been markedly shrinking in size since 2000. In addition to the various water management issues, drought and climate change have impacted water availability throughout the region and increasingly less water reaches Lake Abert each year.

A decades-long drought throughout the Western U.S. is impacting nearly all aspects of life in eastern Oregon. In 2021, the U.S. Drought Monitor reported drought conditions to be the most expansive and intensive drought the western United States has experienced in the past century, with south-central and southeastern Oregon recording the lowest total precipitation relative to the average of anywhere in the state. An article published in early 2022 reported the past 22 years have been the driest two decades since at least the year 800 CE. For nearly half of the past 23 years, Oregon’s Governor has declared a drought emergency in Lake County, further underscoring the severity of water shortages in the Chewaucan Rivier Watershed.

Drought impacts the hydrological system by reducing snowpack in the Fremont-Winema National Forest which in turn, reduces stream flow in the Chewaucan River. Effects of climate change, such as rising temperatures, exacerbate drought by shifting precipitation type from snow to rain, altering the accumulation and timing of snowmelt, decreasing and shifting water availability in streams, and increasing evaporation.

Evaporation of Lake Abert has been increasing since the 1980s. With less than 15 inches of annual precipitation falling directly on the lake and an annual evaporation rate of 40 inches, the lake operates at a deficit every year and is therefore, reliant on inflows from the Chewaucan River to maintain water levels and optimal salinity. When the lake water levels are extremely low, such as in 2014, it takes years of increased precipitation and steady inflows from the Chewaucan River for the ecosystem to rebound.

Prolonged drought may result in more frequent desiccation and a longer recovery period coupled with a longer duration of extremely high salt concentrations and low dissolved oxygen content, hindering brine shrimp and alkali fly productivity and resiliency, and thus, the hundreds of thousands of migratory birds that depend on them. Under these unstable and highly variable conditions, the ecosystem could reach its ecological tipping point or threshold, resulting in irreversible species loss.

A more recently-identified threat to Lake Abert is a pair of pumped storage hydropower facilities. Proposed by Pacific Power as an energy storage solution, this closed-loop system would withdraw water from the Chewaucan River and its tributary Crooked Creek to fill two lower reservoirs. Water would then be pumped uphill to upper reservoirs located atop Abert Rim and Winter Ridge, capturing energy as it falls downhill through pipes back to the lower reservoirs. Additional withdrawals from an already over-appropriated system to fill and maintain reservoirs for the proposed projects will compound water shortages in the basin and further threaten the future of Lake Abert.