Issue link: http://read.dmtmag.com/i/267019
5 8 V I N E YA R D & W I N E RY M A N A G E M E N T | M a r - A p r 2 014 w w w. v w m m e d i a . c o m compared with plant-based water status, measured with a pressure chamber or a leaf porometer. Weather stations provide fore- casts and evapotranspiration data to assist with climate-based irri- g a t i o n s c h e d u l i n g . R e f e r e n c e evapotranspiration, along with an accurate crop coefficient (Kc), can be used to determine the total water a vineyard needs over a spe- cific time period. The Kc must be site specific. Battany also advised maximiz- ing natural rainfall and irrigation water by reducing non-productive losses of water. "Simple reduc- tions in applied irrigation with no other changes in management will tend to result in lower vine transpi- ration and reduced crop yields per acre," he noted. "To avoid these yield reductions, the net avail- able water supply to vines can be increased by reducing preventable soil evaporation losses and by limit- ing excessive cover-crop water con- sumption." Grapegrowers could face tough choices if drought continues and water-use restrictions are imple- mented. One option might be removing vineyard blocks near- ing the end of their useful life and using limited water on more pro- ductive and higher-value blocks. Seasonal conditions may require prioritizing irrigation of some vines over others. Frost protection sprin- klers require higher well rates than drip systems, and frost protection can account for half the annual water use in some years. Growers are looking at wind machines and other frost-protection alternatives. STATEWIDE ISSUES AND PLANNING EFFORTS The California Department of Water Resources (DWR) has iden- tified 515 distinct groundwater basins and sub-basins. California is one of the only western states without a formal state system for regulating groundwater. It has generally been managed locally, and successful programs integrate groundwater protection, extraction, recharge and monitoring for long- term sustainability. The State Water Resources Con- trol Board oversees nine regional boards, each with rulemaking and regulatory authority. The control board released a "Draft Ground- water Workplan Concept Paper" in October 2013, began receiving public and stakeholder input, and is conducting hearings to move a plan forward. Whether implemented at the local, regional or state level, the plan outlines five key elements for an effective groundwater manage- ment program: 1. Sustainable thresholds for water level drawdown and water quality