Since 2011, the Calaveras Winegrape Alliance (CWA) has studied irrigation efficiencies in eight high-elevation vineyards (above 1,000 ft). The project is a result of three U.S. Department of Agriculture Specialty Crop Block Grants.
The goal was to create an irrigation model that is based on forecasted daily high temperatures. It was anticipated that vineyards irrigated using schedules based on 10-day projected high temperatures would save water as compared to vineyards irrigated traditionally. Furthermore, it was anticipated that use of the efficient irrigation model would not compromise the quality or quantity of the grapes.
During the first phase in 2012, a draft model was created and tested in two vineyards. Forecasted high temperatures were manually noted, calculations were performed and a determination was made indicating when to irrigate and at what irrigation rate. The normal weekly irrigation amount was determined based on how the vineyard was irrigated historically. The Model directed the participant to irrigate at either the normal amount, 1.5 times or twice the normal amount.
During the next two phases of the project in 2013 and 2014, the Model was computerized and placed on the CWA website, eliminating the need to manually note the 10-day forecasts and perform calculations. On the website, the grower was instructed to enter their zip code and a recommended irrigation directive appeared on the screen stating to either Irrigate today, Irrigate tomorrow or Don’t irrigate at this time. In addition, it gave a warning that you may need to irrigate in the near future. The Model also stated how much irrigation water should be applied. During these phases the Model was tested in four vineyards over a two-year period.
The purpose of the fourth phase during 2016 was to beta test the online Model in two vineyards while also verifying a reduction in water usage without compromising fruit quality or quantity. Beta testing provided the opportunity to analyze and incorporate feedback and data from growers and identify and correct potential challenges. The goal was to ensure the Model would function properly in a real-world setting. The participating growers indicated they would use the Model again if the website provided a history of their irrigation over the season, eliminated the need to manually track the days between irrigations and provided only one of two irrigation directives each day: Irrigate today or Do not irrigate at this time. The Model was improved accordingly.
Results at a Glance
Phase I – 2012 The draft Model was successfully used in two vineyards. Each vineyard realized a 26% reduction in water usage.
Phase II – 2013 The computerized Model was created and successfully implemented in two vineyards. Each vineyard realized a 28% reduction in water usage.
Phase III – 2014 One vineyard realized a 38% reduction in water usage. The second vineyard had soil with high water-holding capacity and saw a 27% increase in water usage. It was determined that using the Model in vineyards with high water-holding capacity soils or that irrigate only a few times per season may not be beneficial.
Phase IV – 2016 There would have been a 32% reduction in water usage in the West Point vineyard if not for an error in calculating the normal weekly irrigation amount. There would have been a 10% increase in water use in the San Andreas vineyard even if the Model had been followed exactly. The quality and quantity of the grapes was not compromised.
•Model used in eight tests sites
•Successful in six of the eight vineyards – 75%
•Grape quality or quantity was not compromised
•Realized water savings of up to 38%