One of the most frequent questions we're asked as a wine producer and grape grower is how the drought of the last 4 years has affected the vineyard overall. Interestingly, it's not just about the water in Napa's case, or in most of California's wine country for that matter. Common sense says that if you irrigate you should be mitigating the effects of a drought. However, without actual rainfall to push the nutrients in the top layer of the soil down into the root zone the soil quality can suffer. Having an equal or greater effect are the warmer winter temperatures we've experienced over that few winters in addition to the lack of rain. Without cold enough winters to kill of pests such as the Glassy Winged Sharpshooter, you'll see an increase in Pierce's Disease, which is spread by the Sharpshooter. (Coincidentally, it's having the same effect on the Bark Beetle's population surge, responsible for the plague of Oak tree deaths throughout the state.) Additionally the warmer weather has induced far earlier than normal bud break for the last couple of vintages, which while it makes for a more relaxed autumn for winemakers, it increases the window for frost damage at the beginning of the growing season.
All this being said, there is a positive side, in that the lack of water forces the vines to grow deeper searching for water, and thereby stressing the vines. This in turn produces smaller fruit of deeper concentration and complexity and by extension, greater wines. So paradoxically, while we've been pained by this drought, we're also being rewarded with some of the best vintages on record. How sustainable this is is yet to be seen, but 2016 should be an interesting vintage given our substantial rainfall this past winter after 4 years of vine stress. Stay tuned!