Drought Returns to the Pacific Northwest 

Drought is back in the Pacific Northwest.

As our partners at the National Integrated Drought Information System (NIDIS) report in their recent Pacific Northwest Drought Status Update, drought and drought impacts are occurring across our region. But what exactly do we mean by drought? This post looks at ways to interpret different kinds of drought using the US Water Watcher, a new tool CIRC is developing.

Simply stated, a drought occurs when water demand exceeds water supply. Of course, things are never that simple.

Drought means different things to different sectors of society and the environment. This is why when we talk about drought it is often helpful to talk about drought in terms of flavors. (No kidding, climate researchers really do refer to types of drought as flavors. You know, like ice cream.) Drought flavors are named for the specific water resources they track and the sectors they impact.

For example, here in the Pacific Northwest we can experience droughts from low winter precipitation, as we did in 2001. This is the flavor of a meteorological drought. The Pacific Northwest is also known for sampling the flavor snow drought—a period of exceptionally low snowpack like what the region experienced in 2015. Another flavor of drought that we have tasted in recent years is ecological drought—deficits of water availability (large demands but low supplies) that led to impacts on ecosystems, including wildfires.

At CIRC as part of our Northwest Climate Toolbox and with support from NIDIS, we’ve been developing the US Water Watcher, an interface for interacting with drought’s many flavors as well as the many metrics and indices that allow us to identify those flavors.

To do this, the US Water Watcher collates a number of climatic and hydrological indicators of drought, including those from stream gauges, the SNOTEL network, and satellites. This amassing of useful tools allows users to examine and compare in near-real-time measures of drought.

All observations made in the US Water Watcher are ranked against historical observations for the calendar date to facilitate a direct comparison between variables. Values are further color-coded to adhere with the US Drought Monitor drought categories, running the H2O gauntlet from exceptionally wet (dark blue or the top two percentile of historical data) to exceptionally dry (reddish-brown or the bottom two percentile of historical data).

(It’s worth noting that while the US Water Watcher uses the US Drought Monitor’s categories, the datasets visualized by the CIRC tool won’t necessarily mirror the US Drought Monitor’s official map.)

The US Water Watcher tracks five types of broadly defined drought flavors:

  • Meteorological Drought—a period of low precipitation.
  • Hydrological Drought—a period of low water supply in reservoirs, streams, and groundwater.
  • Snow Drought—a period of abnormally low snowpack.
  • Agricultural Drought—when crops experience a negative water balance, for instance when plants lose more water through evapotranspiration than they can absorb from the soil.
  • Ecological Drought—a deficit in surface water supplies that detrimentally impacts an ecosystem.

Much like piling on scoop after scoop of varying flavors of ice cream in a sundae, we often like to combine different drought flavors to contextualize regional drought.

Okay, let’s put the US Water Watcher to work and see what it can tell us about the Pacific Northwest’s current drought conditions. In other words, let’s sample some drought flavors. Take a look at the maps below.

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Figure One: Read from left to right and top to bottom, this map displays percentiles of precipitation over the last 90 days, streamflows over last 28 days, soil moisture, and energy release component for the calendar date July 31st, 2018. These maps were map using the Northwest Climate Toolbox’s US Water Watcher Tool. All observations made in the US Water Watcher are ranked against historical observations for the calendar date to facilitate a direct comparison between variables. (Image Credit: The Northwest Climate Toolbox.)

What you’re seeing are visualizations of roughly four flavors of drought as seen through various metrics. These are precipitation over the past 90 days (meteorological drought), streamflow over the previous four weeks (hydrological drought), soil moisture (agricultural drought), and energy release component (ERC), a calculation of how hot a fire could burn (the energy release part) given recent weather conditions (ecological drought). ERC is used to assess fire danger.

It’s worth noting that there isn’t a one-to-one relationship between a given drought flavor and the metrics we use. For instance, deficits in soil moisture can have agricultural and ecological impacts. So, keep in mind what we’re representing here should be read as a kind of shorthand. Okay, back to the maps.

The maps all show an awful lot of red, indicating extreme to exceptional drought across parts of western Oregon and southwestern Washington, including a wide area of record or near-record lowest precipitation over the previous 90 days. Soil moisture—with implications for agriculture and ecosystems—shows a similar pattern. In summation, for much of the western Pacific Northwest, it hasn’t rained in a while, streams are low, the soil is dry, and fire danger is high.

Drought impacts are being felt most notably in Oregon, which endured a period of substandard snowpack followed by unusually dry and warm conditions since May. The impacts cover the gamut from fire to farms to fish.

Fire
Wildfires have once again marked another Pacific Northwest summer.

As of this writing (August 2nd), multiple large wildfires are burning across the region with the largest number of active fires burning in southwest Oregon near the California border. The map below, produced using the Northwest Climate Toolbox’s Climate Mapper tool, shows active wildfires (those little fire icons) and potential fire danger as measured by ERC. Again, the map shows a lot of red, indicating that fire danger is high.

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Figure Two: Energy Release Component and active fires mapped for August 1st, 2018 using the Northwest Climate Toolbox’s Climate Mapper tool. (Image Credit: The Northwest Climate Toolbox.)

Dry lightning peppered southwest Oregon in mid-July, igniting a large number of wildfires that have burned for a few weeks and shrouded the area in smoke.

A number of large fast-moving grasslands fires, including the Substation fire east of the Dalles in Oregon that burned nearly 80,000 acres have also been seen. Grassland fires like these are typical a full year after a wet winter and spring—like we had from October 2016 to April 2017—and tend to be wind-driven rather than exclusively emblematic of drought.

As we move into August, the fires are likely to continue. In fact, a vast majority of burned area in the Pacific Northwest typically occurs from July 15th onward, meaning that we’ve got a ways to go before we can expect the fire season to die down.

Farms
Wildfire impacts carried over to farms this summer.

The Substation fire devoured a large chunk of wheat fields in Oregon’s Wasco and Sherman counties. Sadly the wheat was about to be harvested. Initial estimates were that 1–2 million bushels of wheat were lost in the flames. The loss is estimated to between $6 million and $12 million.

Moisture deficits over the past three months have also taken their toll, especially on rain-fed crops and pastures in Washington and Oregon.

By contrast, irrigated crops in other parts of the Pacific Northwest have had access to stored water; particularly in Washington where above normal precipitation fell this past winter. Oregon tells a different story.  Many of the state’s reservoirs have used up their carryover—or their water savings account—from the previous two wet years and are now draining ahead of their typical schedule. In southern Oregon, the most senior water rights holders—the people who get the first claim to the available water—are being regulated.

Drought is causing tough conditions for pasture, and some producers are having trouble finding enough water for their cattle. Ranchers in southern Oregon are reporting that they have had to purchase hay this year, which isn’t a common occurrence. Some are supplementing their cattle feed with alfalfa.

Fish
Fishing restrictions have been enacted in the Umpqua River in western Oregon due to critically warm stream temperatures for steelhead and salmon. The combination of very low flows—including recent daily record low flows—due to subpar precipitation and warm temperatures have allowed water temperatures to warm faster than usual.

This list of impacts is not complete, but it should give you a sense of what’s been going on.

What’s Next?
To put it mildly, the outlook for our current drought situation is not rosy as we are near the climatological apex of summer in terms of warm and dry days.

A reprieve from the heat and chance for wetting rains in the next week or so could help temporarily ease drought intensification. However, odds are stacked for warmer and drier conditions across the region for the latter half of August. That means we should expect conditions to worsen before they get better.

There could also be an El Niño event brewing in the tropical Pacific, which could materialize this winter. Because El Niño winters are not known for busting droughts in the Pacific Northwest, drought could be a story we’re tracking into next spring.

We’ll keep you updated.

This post is part of Northwest Climate Currents, an ongoing series that uses the Northwest Climate Toolbox and the data it collects to help us understand and prepare for our region’s climate events. The Northwest Climate Toolbox is a suite of free online applications designed by CIRC researchers and intended to help foresters, farmers, and water managers respond to and prepare for climate variability and change and related impacts.

 Acknowledgements: The Northwest Climate Toolbox is funded in part through the NOAA Regional Integrated Sciences and Assessments (RISA) program and National Integrated Drought Information System (NIDIS).


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OSU_icon_key_01Key Terms:

  • Agricultural Drought—when crops experience a negative water balance, for instance when plants lose more water through evapotranspiration than they can absorb from the soil.
  • Ecological Drought—a deficit in surface water supplies that detrimentally impacts ecosystem.
  • Energy Release Component (ERC)—a calculation of how hot a fire could burn (the energy release part) given recent weather conditions
  • Meteorological Drought—a period of low precipitation.
  • Hydrological Drought—a period of low water supply in reservoirs, streams, and groundwater.
  • Snow Drought—a period of abnormally low snowpack.

OSU_icon_graph_01Pics and Figures: 

Figure One/Featured Image: Read from left to right and top to bottom, this map displays percentiles of precipitation over the last 90 days, streamflows over last 28 days, soil moisture, and energy release component for the calendar date July 31, 2018. These maps were map using the Northwest Climate Toolbox’s US water Watcher Tool. All observations made in the US Water Watcher are ranked against historical observations for the calendar date to facilitate a direct comparison between variables. (Image Credit: The Northwest Climate Toolbox.)

Figure Two: Energy Release Component and active fires mapped for August 1st, 2018 using the Northwest Climate Toolbox’s Climate Mapper tool. (Image Credit: The Northwest Climate Toolbox.)


John Abatzoglou has been a CIRC team member since 2010. A climate and meteorology researcher at the University of Idaho and self-described “weather weenie,” John leads CIRC’s Northwest Climate Toolbox effort. He has participated in the creation of several CIRC-related Climate Tools, including Climate Engine and Integrated Scenarios.  


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