Prepared by Robert Shibatani exclusively for Maven’s Notebook

As of June 30, 2020

The ability of the State to “ride” on its established carryover storage was on vivid display this month. Our north CVP reservoir storage as of today, stands at 96% of our 15-year average. We have 7.579 MAF in storage (or 66.7% of total North CVP storage capacity). Shasta, Trinity, and New Melones, the 3 largest north CVP reservoirs are holding in good shape; they have storage quantities that are 92, 100, and 112% of the reservoirs’ 15-year averages, respectively. Oroville Reservoir stands at about 86% of its 15-year average having 2.157 MAF in storage.

Despite persistent claims of “mega-droughts” plaguing the U.S. Southwest, at least north CVP/SWP storage capacity is fine for likely the remainder of the WY. From a weather perspective, we have been fortunate so far temperature wise and barring any unforeseeable extended heat waves, we should be able to keep direct reservoir E and terrestrial ET atmospheric losses within acceptable ranges. Current CVP reservoir releases are at or about 15-year medians so there are no noticeable delivery releases beyond normal.

The State existing snowpack is now gone. Water remains in basin vadose/phreatic storage and baseflows are being maintained, and that is what is making up all stream and river flows throughout the State. Northern Sierra Precipitation 8-Station Index (as of July 3rd) is 31.7 inches (or 63% of average for this date) and the 2nd driest to date. The San Joaquin Precipitation 5-Station Index is 24.5 inches (or 63% of average) and the 3rd driest to date. The Tulare Basin Precipitation 6-Station Index is at 18.6 inches (or 67% of average).

As stated last month, despite below normal precipitation accumulations for the WY, northern California water supplies are sufficient for the remainder of the WY. In fact, for some north State purveyors, there is enough to begin seeking approval for temporary transfers to large south-Central Valley Ag water users.

Robert Shibatani, a physical hydrologist with over 35-years combined academic, legal, consulting and water advisory expertise, is an international expert witness on reservoir-operations, climate change hydrology, commercial flood damage litigation, and water supply development. He is Managing Partner for The SHIBATANI GROUP International, a division of The SHIBATANI GROUP Inc. and resides in Sacramento, California.

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