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26 WINES&VINES November 2015 Grounded Grapegrowing A s we finish our fourth year in Cali- fornia with below normal rainfall, having enough water for irrigation remains a critical issue in many vine- yards around the state. Surface water has been in short supply in many areas, as many irrigation districts do not have enough water to honor customers' allot- ments. If growers have the option, they are rely- ing on groundwater to replace scarce surface water. This has resulted in lowered water table levels and, in some cases, dry wells. The California State Department of Water Resources has identified groundwater basins that are either "high" or "medium" priority basins that will require water elevation monitoring. Believ- ing that the best solutions will probably be based on local knowledge, the state is asking land own- ers or local agencies in these basins to develop groundwater sustainability plans that will moni- tor well levels and also come up with ways to reverse the declining water tables. It is clear that water use for all of California will be much more closely monitored than in the past. Making intelligent choices in vineyard tech- nology will be important in helping growers apply their limited water resources wisely, whether they choose the latest tech tools or more traditional equipment for measuring and manag- ing irrigation. New technologies to manage water use Tule Technologies Tule Technologies' crop water use monitoring measures actual evapotranspiration (ET) in your vineyard using a technology called surface re- newal. A Tule Actual ET Sensor device can moni- tor up to 10 acres of vines, depending on site conditions. The device itself is fairly small, and installation can be done in under an hour. The sensor measures precisely how much water is being removed from the soil by the vines and reports in real time. Tule software will then calculate how much water is needed to meet the consumptive use of the vines based on a preset irrigation strategy. Using a crop coefficient, or the percentage of evapotranspiration you need to apply to meet plant growth needs, the software calculates the amount of water to apply to the vines. If you are practicing regulated deficit irriga- tion, the crop coefficient is usually much less than ET. On the other hand, if you are farming a vine- yard with a big canopy and a large crop, the crop coefficient may be very close to ET. The Tule Tech- nology tech rep and grower work together to set plant growth targets (crop coefficient) at the be- ginning of the season, develop the irrigation strat- egy and program it into the software to set irrigation system recommendations. Sensors placed on the irrigation system then track how much water is actually applied and measure water stress level, known as the Plant Response Index (PRI). The PRI accounts for cli- mate condition changes. A decrease in PRI means an increase in the water stress level and corre- lates with other measures of plant water stress like leaf water potential. The PRI gives you very fast feedback on the outcome of any water that you apply and how the vineyard is responding under the present weather conditions. The data are sent by cell phone, and growers can see dis- plays either on a computer screen or smart phone. A simple and clear display makes the information very easy to understand. Finally, the Tule software will create an "at- mospheric demand forecast" to help an- ticipate what water demands may be in the week ahead. Using weather forecasts, the software will predict whether you need to apply more water, or if your present schedule is adequate. If weather is cooling, a forecasted decrease in the at- mospheric demand indicates that the next irrigation cycle can be decreased in amount or post- poned. The system also cre- ates reports for the previous week's ac- tual ET and irriga- tion activity and next week's fore- casted water demand that n GLENN T. McGOURTY Make Your Irrigation Program More Precise With Technology KEY POINTS Vineyard water management will become even more important as Cali- fornia requires local agencies and grow- ers to develop groundwater sus- tainability plans. Examples of three types of new tech- nology show how advanced the mon- itoring of soil and plant water status has become. This column also reviews more traditional water- sensing equipment such as pressure bombs and C-probes.