Signs of the western drought

As I traveled through northern California into Oregon last month, evidence of the severe drought lingering in the west was apparent. Late summer and early fall are typically dry periods in California with the grasses having long since turned golden. But there were perhaps other signs of the on-going drought: water levels at Lake Shasta were very low revealing a large band of reddish soil between the reservoir and the treeline; pines in northern California and southern Oregon appeared stressed; normally glaciated Mount Shasta, nearly the highest point in California, had just thin ribbons of snow on its southern slopes.

Low water levels at Shasta Lake (a major reservoir in northern California).

Pines in the vicinity of Mt. Shasta in northern California and
into southern Oregon looked perhaps unusually stressed with
significant amounts of dead needles.

In California the drought is now in its fourth year, and concern finally reached the level where mandatory reductions in water usage by residential consumers were put into place. Other parts of the west are also in drought. Nevada is nearly as dry as California. Oregon and Washington have had abnormally low precipitation this year. The maps of drought conditions for the United States, updated weekly by the U.S.Drought Monitor, show that the western U.S. as a whole is quite dry.

Mt. Shasta with low snow coverage.

One useful metric of drought conditions is the PalmerDrought Severity Index. The index incorporates both precipitation and temperature information to indicate drought intensity. Values ≤ -4 indicate “extreme drought”; and values between -2 and -4 indicate “moderate” or “severe” drought. Trees are also excellent sentinels of overall environmental conditions because their growth patterns integrate the various stressors they experience such as temperature, soil water content and nutrient availability. Thus tree ring data provide excellent annual historical records of environmental conditions.

On-line I located the work of a team from NOAA’s Nation ClimaticData Center that used hundreds of tree ring samples to study long-term changes in drought intensity throughout the U.S. I downloaded and plotted Palmer Index data for the last 500 years in the northern California region. Tree ring data from 26-55 samples cover this time period. I am definitely not an expert on the science of drought, but to me the data suggest that normally there is substantial year-to-year variation in drought conditions in this region. Some longer-term patterns can also be discerned from the time series. For example, from about 1915 to 1935 – a period coinciding with the dust bowl in the Midwestern US – northern California appeared to be in an extended drought.

Palmer Drought Severity Index data reconstructed for northern California from tree ring data over the last 500 years. The 
blue lines indicate annual values; the thicker red line is a ten year running mean. The time series ends in 2003, so the
current drought is not shown on the figure. Data source: NOAA NCDC.

Recent drought status in the continental U.S. as measured by the Palmer Index. Map source.

Only time will tell if California experiences a fifth year of drought. With a strong El Nino currently developing in the eastern Pacific Ocean, chances are that greater than average precipitation will fall in California this winter and some relief will come. It has also been a warmer year than ever, so more of that precipitation may come as rain rather than snow.

Crater Lake

Crater Lake National Park was the last significant stop on my recent trip to the Pacific Northwest. Located about 50 miles north of the California border, it is the only national park in Oregon. The park centers on the magnificent lake with its deep, cold, and intensely blue waters.

Crater Lake and Wizard Island (center) from the southwest side of rim drive.

Wizard Island is a small crater that formed inside Crater Lake
after the massive eruption of Mount Mazama (NPS 2013). With
its beautiful shape, it is my favorite feature of the Park.

The crater in which the lake rests was formed by a massive volcanic explosion some 7700 years ago. Prior to this cataclysmic eruption, Mount Mazama was one of the highest peaks in the Cascade Range, reaching about 12,000 feet in elevation (NPS 2013). The area has breathtaking vistas and holds fascinating lessons in geology.

I camped for a single night at Lost Creek campground, a small site among pines on the eastern slope of the mountain. It was the night of the lunar eclipse and blood moon and Crater Lake was the perfect location for sky watching. At about full eclipse in the late evening (approximately 8 PM PDT), hundreds of stars were visible in the darkened sky because of the obscured moon. Later, after the eclipse lapsed, the landscape became much more illuminated from the brilliant full moon. I drove back down the road a few miles from the campsite to the pinnacles area that I had visited just before sunset.

Pinnacles at the southeast side of the park. The discreet bands of color show
the evolving composition of volcanic material as it was erupted from Mount
Mazama 7700 years ago (NPS 2013).

I have made a few day trips to Crater Lake in the past, but saw the pinnacles for the first time on this trip. Formed during the last eruption, they stand as spires on both sides of a wide valley cut into the eastern slope of Mount Mazama. In essence, during the eruption large flows of hot ash poured down the slopes of the mountain. Heated gases rose through the ash to escape into the atmosphere over time, hardening columns of mud (called “tuff”) surrounding the gaseous vents. Finally over time, erosion removed the softer ash but not the more hardened columns of mudstone surrounding the vents, leaving a landscape of spires for us to admire today (NPS 2013).

Crater Lake from the trail at Cleetwood
Cove.

In the morning following a cold night of camping, I hiked down the only trail that leads from the rim of the crater to the lake itself. It is a short but moderately steep trail that passes through light conifer forest. The water of the lake was calm, reflecting sparkles from the sun in the east. At the end of the trail there is a boat launch (for paid tours to Wizard Island), and a small shack housing a water level measurement station. I put my feet in the cold lake in the warm morning sun.

The history of Crater Lake is one of violent geologic forces, but the placid lake and singing birds on a warm morning in early fall, and the green carpets of forest on Mount Mazama’s slopes belied its turbulent past.

Reference

National Park Service (2013). Crater Lake National Park. Geologic Resources Inventory Report. Natural Resource Report NPS/NRSS/GRD/NRR-2013/719

The pinnacles illuminated by the full moon.

The eclipse and blood moon from the Park.