Low Precipitation Records Spell Out Drought Across Valley
When California’s 2013-14 precipitation year came to an unlamented, hot, sunny conclusion June 30, the records left behind spelled out drought in all sorts of discouraging ways.
Among those is the natural shortage of water that is among the factors in a U.S. Bureau of Reclamation decision to allocate no Central Valley Project water this year to Friant Division users.
The National Weather Service in Hanford reported its major southern San Joaquin Valley reporting stations were all far below average:
• Bakersfield, 2.41 inches of rain between July 1, 2013-June 30, 2014, its third driest on record, compared with 3.15 inches the previous year and an average of 6.47 inches.
• Hanford, 2.82 inches in 2013-14, down from 3.60 inches in 2012-13, and just 28% of the normal of 10.10 inches.
• Fresno, 4.81 inches in 2013-14, its second driest on record, down from 5.67 inches in 2012-13. Normal is 11.50 inches.
• Madera, 4.58 inches in 2013-14, down from 8.22 inches in 2012-13. Normal is 12.02 inches.
RECORD 3-YEAR DROUGHT
Fresno completed its worst-ever three-year drought period. Only 18.60 inches of rain fell during the 2011-14 period, breaking an 80-year-old record of 19.80 inches set from 1931-34.
Ironically, the 1931-34 drought was among the major factors sparking support for the CVP’s initial development, including construction of Friant Dam from 1939 44 as well as the Madera, Friant-Kern and Delta-Mendota canals.
Sealing the valley’s dry fate in 2013-14 was a 52-day early winter dry spell in which no precipitation was recorded.
Only a few light to moderate spring storms and scattered spring thunderstorm downpours kept the just-ended precipitation year from being a complete catastrophe.
DRY IN SIERRA NEVADA
Also far below average were mountain rainfall and snow accumulation totals.
Typical was the five-station San Joaquin River watershed index (which includes key stations at Huntington Lake and North Fork in the upper San Joaquin River basin). Its average precipitation was 19.2 inches, third lowest on record (behind 1923-24 and 1976-77). The total was far below the index’s average of 39.5 inches.
Huntington Lake, at an elevation of 7,000 feet, had just 16.92 inches of precipitation compared with an average of 42.73 inches.
Snowfall amounts were very low and the snowpack melted early and rapidly at all but the highest elevations. By late June, when elevations above 9,000 feet usually have some snow remaining on the ground, many slopes along the Sierra Nevada crest were bare.
Nor has there been any recent thunderstorm activity that might produce summer mountain rainfall.
The California Department of Water Resources predicts San Joaquin River full natural runoff in the water year that ends September 30 should add up to about 500,000 acre-feet, only 27% of average.
The peak snowmelt season ended in May. The April-through-July period, which usually accounts for the San Joaquin’s greatest total runoff, is expected to yield between 369,000-390,000 acre-feet, 31% or less of average. The calculated natural flow at Friant, as if there were no dams, has been staying somewhat below 1,000 cubic feet per second in recent weeks.
Millerton Lake storage behind Friant Dam has stayed surprisingly high, ending June at about 326,000 acre-feet, 62% of capacity. However, actual Millerton Lake inflow has been substantially reduced by lower power company releases and now is mimicking the river’s calculated natural flow.
With extremely limited releases into the Friant-Kern and Madera canals (please see related story, front page) and Friant Dam releases for downstream riparian pumpers and the San Joaquin River Exchange Contractors now up to 1,300 cubic feet per second, Millerton storage is declining.