Kern River Basin Snow Melt Underway
By Steve Lafond
Valley Ag Voice
I’m sure by now, many readers have noticed water is flowing again in the Kern River through the heart of Bakersfield. The sight of a “wet” river through town is not only visually pleasing and comforting, but the recharge that occurs is helping to fill our underground aquifer. It is simply amazing the work water men do, even in the midst of a much below normal water year on the Kern.
At Isabella Lake, the surface elevation of the reservoir is rising steadily, as Kern River inflow is nearing it’s peak discharge rate for the season. There are expectations the lake will fill to nearly 250,000 acre-feet later this spring, approaching 45% of the reservoir capacity.
The final State of California official water supply report for this year was issued on May 7, 2020 and calls for an April-July runoff on Kern River of 240,000 acre-feet, 52% of normal. Water year runoff for the period of October 1, 2019 through September 30, 2020, is projected to reach 425,000 acre-feet, or 58% of its long-term average yield. With the temperatures quickly rising on the San Joaquin Valley floor, outflow from Isabella Dam has surged, currently flowing at the rate of approximately 1,000 cubic-feet-per-second (“cfs”). Based on current water supply data, the Kern River, below Isabella Dam, may reach as high as 1,500 cfs later this summer.
Water Year Memories
Kern River 1983 Snow Melt Runoff Tops 330% of Normal
Once upon a time, in a watershed not far away, it rained and it snowed, much like it would have during the last ice age, some 40,000 years ago. Through months of wet, saturating storms, the mountain snowpack became so deep that aerial snow markers disappeared, completely buried by the winter’s onslaught. Manual snow surveys were delayed due to threat of avalanche, and creeks topped their banks. Even the hot summer sun could not completely melt the bountiful snowpack that year. This was the Kern River Basin during the winter of 1982-1983 and record snowmelt that followed, immortalizing the legend of Kern River for all time.
October of 1982 ushered in the beginning of a new water year on Kern River. The rains moved in early, with lofty precipitation amounts at Isabella Dam registering 217% and 266% of normal for October and November 1982, respectively, and as if that wasn’t remarkable enough, December 1982 followed with a blockbuster rainfall tally of 186% of normal. Back at the City of Bakersfield Water office, there was no word of an oceanic phenomenon underway that would cause a warm pool of water to drift easterly along the equatorial Pacific, bringing with it significant changes to the global weather pattern. No one spoke of the immediate future in terms of sea surface temperatures and their connection with flooding rains. Little did we know the storm track would target the Kern River Basin for much of the winter period, leading to record precipitation, snowpack, runoff, and storage. The term, “El Niño”, and its potential impact on Kern County water supply, had yet to be proclaimed.
Mother Nature had in mind the perfect recipe for a wet water year on the Kern, and wasted little time announcing it. Right out of the gate we were treated to six consecutive months (October 1982 – March 1983) of much above normal precipitation, a weather anomaly not witnessed since long before Isabella Dam was constructed. The winter of 1982-83 was atypical in that wet episodes were rarely followed by extended periods of dryness. The storms came through every 3 to 5 days, like clockwork. Precipitation as recorded at Isabella Dam during the October 1982 – March 1983 period ranged from a low of 182% of normal (4.31”) during January 1983 to a high of 377% of normal (5.96”) in March of 1983.
By late May, warming temperatures in the southern Sierra brought the Kern River tumbling down, resulting in record high flows between May 23, 1983 and May 31, 1983. Peak Kern River natural flow occurred on May 29, 1983 at 14,038 cfs, the highest snowmelt flow ever recorded. Record setting Kern River runoff continued into June of 1983, establishing record high flows over the period of June 9 – June 20. Meanwhile, outflow from Isabella Dam was pushed to record heights, culminating on June 29, 1983 with 7,237 cfs, the greatest outflow in the history of the Isabella Dam project.
Isabella Reservoir storage began to exceed the lake capacity of 568,075 acre-feet as of June 13, 1983. On this date, water began pouring over the Isabella Dam Spillway for only the third time in dam history (1969, 1980). Water continued to flow over the spillway through July 20, 1983. Peak spillway discharge amounted to 5,721 cfs and occurred on July 6, 1983, the same date Isabella Reservoir reached its highest level in history with 630,825 acre-feet of storage.