How did we do this water year, and what is the status of the drought?
Long-term rainfall data indicate that, on average, the Napa Valley receives 7% of its annual rainfall during the month of April. Based on the data collected from the Napa County ALERT rain gauging stations during April 2016, the Napa Valley received 4% of its annual average. Although it was an underachieving month, the rainfall we received increased the total for the year to 100% of our mean annual precipitation. Rainfall amounts recorded at these stations during April ranged from 0.79 to 2.88 inches. Rainfall totals for Water Year (WY) 2015-16 range from 23.88 inches on Mt. George to 54.17 inches on Mt. St. Helena.
Drought conditions continue, but remain improved from one year ago. Napa Valley is classified as “Abnormally Dry,” the least-severe drought category, and the east side of the County is in moderate to severe drought.
The local municipal supply reservoirs are full, and Lake Berryessa remains low at 74% of its historical average storage for the month of April (65% of total capacity).
On average, we get 3% of our annual rainfall during the month of May and 2% between June 1 and September 30, so we may be able to add a little more to these totals, but with the hydrologically-active part of the water year behind us, I plan to suspend these updates until WY 2016-17. Please keep in mind that while we experienced some relief during WY 2015-16, conditions next year are impossible to predict. WY 2016-17 could bring continued relief, a return to wet conditions, or a recurrence of severe drought. Use water wisely.
– Paul Blank, Senior Hydrologist, paul@naparcd.org