tl;dr: Very Very Wet. Total rainfall exceeds 1982-1983, but current snowpack is much lower at this point in time and more in line with the the Spring of 1998 or 2011.
The Final Water Forecast for 2017 was released Monday May 8th, with the Water-Year forecasted for Wet. Specifically it’s forecasting the American River below Folsom at 7.810 million acre-feet (MAF), with 3.500 or greater being considered Wet1. In fact, we’ve already had 5.922 MAF of unimpaired runoff, so even if the heaven’s remained dry through the end of this water year, we’re already locked in on it being a Wet classification.
There has been a lot of talk in the media as of late, of different regions setting all time rainfall records, and well there should be. But we should be careful to understand that just because this is the biggest water year on record, does not mean that we’ll see the largest May and June flows on record.
While this year will go down as the highest water year on record, but much of that water has already moved into the ocean. This can be most clearly seen by looking at the current California snow water content, which shows that there is significantly less water still on the mountains as compared to the 1982-1983 water year on May 12th.
Not pictured but worth noting: The Northern and Southern California current numbers are already significantly below the 1998 and 2011 numbers.
For comparison, the unimpaired runoff for the American River below Folsom in 1983 in 1,000 Acre-Feet was 983 for May and 942 for June2. Forecast for 2017 are predicting 940 for May and 695 for June3. While 1998 had 694 for May and 787 for June4, and 2011 had 684 in May and 793 in June5. So if those predictions hold, we should see May flows higher than we did in 1983, however June will likely drop to smaller flows than we saw in June of 1998 and 2011.
This final forecast is technically only valid until early October when the final numbers are crunched, but it’s a reasonable assumption that the following will not change barring an act of congress6.
It’s worth a reminder that how quickly or slowly the snowpack melts could result in significantly higher flows during the remainder of Spring and early Summer.
The final water year report should be released sometime in October.
As of May 12, 2017 – 10 AM
Note: This page is updated with current forecasts as they become available. Previous forecasts are archived for reference.