Rainfall Update – January 2017

How are we doing so far this Water Year?

The Napa County Rainfall and Stream Monitoring System, also called the ALERT System, is a network of automated rain and stream gauges installed throughout the County that provides advanced warning of potential flooding.  Although flood warnings are the primary purpose of the ALERT System, data records from the 17 rain gauges can be assessed to better understand current water conditions in the Valley.

Rainfall is measured as a depth, in inches, and rainfall depths vary by location.  So far, rainfall totals for Water Year (WY) 2016-17, from October 1 through January 31, range from ~ 26 inches in the eastern hills at the south end of the Valley to 51.53 inches on Mt. St. Helena.  In order to assess rainfall across the whole Valley, we compare the total for each gauge to the annual average for that specific gauge.  Even though Mt. St. Helena has received twice as much rain so far this year than the southern end of the Valley, both locations are between 105% and 110% of average. 

Altogether, the 17 ALERT rain gauges indicate that so far the Napa Valley as a whole has received 110% of its average precipitation for the year.

– Paul Blank, Senior Hydrologist, paul@naparcd.org