Walsh Vineyards has compiled some area weather data to help our clients quantify their "risk assessment" for the drought conditions in our area. We are currently working with them on management options for the 2014 growing season. This is primarily directed to properties that rely on annual rainfall to fill ponds for use in irrigation.
Three-Month Rainfall Probability Outlook
Snow Pack "Year Ago" Comparison (Source: NOAA)
What this means to Napa and Sonoma area vineyards as of late January:
- There is a 40% probability of below average rainfall from February through April. We estimate below average rainfall will result in ~7" of rain for the area.
- There is a 30% probability of normal rainfall from February through April. We estimate average rainfall will result in ~10" of rain for the area.
- There is a 30% probability of above average rainfall from February through April. We estimate that above average rainfall will result in ~13' inches of rain.
NOTE: This is very generalized, rainfall variation across Napa and Sonoma Valley's are significant. This is very general data that is intended to be a reference point only.
Management Considerations
Walsh is working under the assumption that there is an equal to (or greater than) 70% chance of a severe drought. In other words, client properties with ponds only (and no adequate supplemental well) will likely not meet what we consider a "threshold" for their water collection.
A common "threshold" of rain that generates available surface water runoff is around 11" of rain. Without 11" of rain, the rain water tends to get "soaked up" into the ground and water therefore does not run into drainage systems to get collected into storage areas.
For the same reason, less than 11" of rain also impacts stream water collection efforts, as water flow does not reach adequate C.F.S. (Cubic Feet Second) for pumping water from streams. It is unknown the extent that this impacts subsurface water (wells).
Water supply management includes having an understanding of your ponds capacity, modeling of evaporation, potential leakage loss, staff gauge, and known unusable water below the pumping system.
Managing vines for water status during every season, and especially this season, is an important tool in maximizing the usefulness of any available vineyard water. Walsh clients utilize various techniques to measure vine water status including: NDVI images, pressure chamber, neutron probe, capacitance probes, shoot tip indexing, historical irrigation records, and weekly scouting.
Farm plans and budgets are being impacted as you read this. Here are a number of items that we will be looking at with our clients over the coming months:
- Review Crop Insurance
- Removing competing cover crops early
- Review ECP's and renew cover crops where permissible
- Bring in wind machines to conserve water where sprinklers are normally used during frost
- Prioritize blocks (high value vs lower value)
- Farm a "small vine"
- Lower shoot counts
- Fewer clusters
- Judicious irrigation, promote minimal (but adequate) vegetative growth
- Consolidate reservoirs to minimize exposed water surface area (minimize evaporation)
- Understand outside sources of water from the City and waste water treatment facilities.
- For vineyards that are not impacted by the drought, condition systems early and perform bud-break irrigations to insure regular seasonal canopy growth.
These are some of the discussions that are currently taking place with our clients, and throughout the valleys. Out clients will continue to monitor what has already become the main management factor in the 2014 vintage.
Thank you, Walsh Vineyards Management