What does Water Year 2017-18 looks like so far?
Annual rainfall totals measured last year (Water Year 2016-17) at the Napa County ALERT rain monitoring stations were the highest in the system’s history, as opposed to Water Year 2006-07 being the lowest. Totals between 44 -100 inches of rainfall were recorded, compared to averages between 25 -52 inches for the stations. These amounts equate to approximately 180% of mean annual precipitation. Long-term rainfall data reveal that it was the third wettest year in the 114-year record for the Napa area, right behind the 1981-82 and 1982-83 water years.
October 1, 2017 marked the start of Water Year 2017-18, and so far, rainfall totals recorded at the stations range between 3.33 inches (Lake Hennessey) and 7.14 inches (Mt. Veeder), approximately 14% of mean annual rainfall. On average, the Napa Valley receives approximately 5% of its annual rain during the month of October, and 10% during November. We had a dry October this year, receiving only 0.7% of mean annual rainfall; however, November was above average at 13.6%. Overall, totals are only slightly below average for the year.
– Paul Blank, Senior Hydrologist, paul@naparcd.org