By Steve Lafond
Special to the Valley Ag Voice
The Kern River, commonly referred to as the “River of Feast or Famine”, is at it again. One year removed from a 200% of normal runoff, the Kern River has been locked under dry weather conditions since the first of the year, sending ripples of consternation throughout the local farming community. Since the first of January 2020, a meager .94” of rain has been recorded by the U.S. Army Corps of Engineers at Isabella Dam, compared to 15.85” over the same time period last year, leaving the Kern River watershed starving for moisture.
Following is a mid-winter snapshot of the snowpack and forecasted runoff conditions on the major Sierra watersheds vital to Kern County
Kern River Basin
The February 1, 2020 forecast issued by the State of California Department of Water Resources for Kern River runoff during the 2020 April through July snow melt period is for 66% of normal, or approximately 300,000 acre-feet. The Kern River Basin snowpack was surveyed by State of California and United States Forest Service personnel during the last week of January 2020 with manual measurements of snowpack depth and water content drawn from sixteen long-established snow courses in the Kern ranging in elevation from 7,300’ (Dead Horse Meadow) to 11,350’ (Big Horn Plateau). The survey found the water content of the basin to be 49% of the April 1st average and 80% of the February 1st average. The February 1st forecast of Kern River runoff assumes median precipitation amounts will occur over the Kern River watershed subsequent to the date of forecast. Actual precipitation received after February 1st will be reflected in the first of the month forecasts to be distributed by the State of California for March, April and May of 2020.
San Joaquin River Basin
Snowpack conditions in the San Joaquin River Basin, the major source of water for the Friant-Kern portion of the Central Valley Project, were also below normal. Snow depth and water content surveys of 22 snow courses, ranging in elevation from 6,800’ (Poison Meadow) to 11,450’ (Mono Pass) confirmed the San Joaquin River Basin snowpack to be approximately 41% of its April 1st average and 65% of the February 1st average. Based on the most probable future weather conditions, the 2020 San Joaquin River April through July inflow to Millerton Lake is expected to yield 880,000 acre-feet, or 72% of normal.
Feather River Basin
The Feather River, a major tributary to the Sacramento River, provides the primary watershed for the State Water Project. During late January of 2020, manual snow survey measurements of snow depth and water content in the Feather River Basin were performed. Sampling of the Feather River snowpack occurred at numerous snow course locations ranging in elevation from 4,600’ at Chester Flat to as high as 8,250’ at Lower Lassen Peak. The February 1, 2020 snowpack conditions in the Feather River Basin were reported at 44% of its April 1st average snow water content and 66% of the February 1st average. Based upon the State DWR February 1, 2020 forecast, the Feather River is likely to flow into Lake Oroville with 1,100,000 acre-feet of water (65% of normal) during the 2020 April-July snow melt period.
2020 Kern River/Isabella Lake
On February 1, 2020, Isabella Reservoir held 169,282 acre-feet of storage, approximately 104% of normal for this date. Based on the current lake level, coupled with the February 1, 2020 State DWR snow melt runoff forecast along with Kern River historical data, maximum storage at Isabella Reservoir for 2020 should near 250,000 acre-feet later this spring. Kern River inflow to Isabella is expected to top out close to 2,000 cubic feet per second (cfs) during the height of the 2020 snow melt period. A 66% of normal Kern River yield in 2020 should allow for summer-time water releases below Isabella Dam to be in the range of 1,500 cfs. Last year, with bountiful Kern River runoff, outflow from Isabella Dam reached 5,400 cfs. Depending on numerous factors, such as actual precipitation received over the balance of the rainy season and strength of Kern River water demand over the peak 2020 water use period, Isabella Dam storage may be drawn down to 150,000 acre-feet or lower by years end.
February on the Kern: Facts, Notes
Feb 1 – On this date in 1963, 7.35” of rain was recorded at Johnsondale, California, while 1.48” fell at Isabella Dam. The USGS gage station at Kernville was knocked out of service as the North Fork of the Kern swelled to flood stage. Isabella Reservoir gained 29,930 acre-feet on February 1, 1963 alone; the Kern River established a new maximum natural flow for the day at 15,584 cfs.
Feb 6 – On this date in 1937, the flow of Kern River at First Point began a sharp rise from 438 cfs to its eventual peak discharge of approximately 20,000 cfs. The February 1937 flood disabled the First Point station such that maximum and minimum flow readings were not available until late September of that year.
Feb 13 – On this date in 1991, Kern River natural flow (165 cfs) was mired in a 37 consecutive day run of record setting minimum flows (since 1893) which began the 22nd of January 1991 and continued thru February 27, 1991. Only then did moderate precipitation occurring above Isabella Dam cause enough of an increase on the river to break out of the record setting dry trend. The late February storm was the precursor to the “March Miracle” of 1991.
Feb 17 – On this date in 1986, rain fell in the Kern River watershed for the sixth consecutive day. The storm period of February 12-21, 1986 yielded 3.30” at Isabella Lake and 13.1” at Pascoe snow sensor (9,150 elev.). The State forecast of Kern River April-July inflow to Isabella increased from 320,000 acre-feet as of February 1, 1986 to 700,000 acre-feet on March 1, 1986.