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the first month of the season, when the water management between these two practices was different, indicated that K c and water use were lower in DS systems relative to WS systems when there was only one irrigation flush during this period, while two or three irrigation flushes resulted in similar values between the two systems.

The crop coefficient (K c) values of rice paddy are important for estimating accurate rice crop evapotranspiration (ET c), water transfers planning, efficient irrigation management, and hydrological studies. In this study, ET c was measured and a generalized K c curve was calculated for paddy rice in the Sacramento Valley, California. Field experiments were conducted in three rice paddy fields during the 2011-2013 growing seasons. Surface renewal analysis, after calibration using eddy covariance method, was applied to obtain sensible heat flux values from high-frequency temperature readings; latent heat flux densities were characterized by the residual of the energy balance method. The results revealed that there is considerable variability in rice water use both spatially and temporally. The average 3-year measured seasonal ET c of the experimental fields ranged from 690 to 762 mm in Butte County and from 681 to 813 mm in the Colusa County. A mean daily seasonal ET c of 5.3 mm d −1 and midseason ET c of 5.8 mm d −1 was observed. The rice K c values were lower than those commonly used to estimate rice ET c during the midseason and were greater than expected during early growth before canopy closure. For a typical growing season of 145 days, the K c values were estimated as 1.10, 1.00, and 0.80 for the initial-growth, midseason, and late-season stages, respectively. The generalized K c curve is quite accurate for practical application and enables growers to determine rice crop water use in a reliable, usable, and affordable format. The proposed K c information can be used to refine the estimates of rice consumptive water use in the Sacramento Valley for the purpose of water transfers to water-short areas of the State. These K c values are likely applicable to other locations having similar climate to the Sacramento Valley in California.

T he recent passage of the Sustainable Groundwater Management Act (SGMA) in California obligates increased levels of management in high-and medium-priority groundwater basins in the near future in order to achieve long-term sustainable groundwater conditions (DWR 2014). An immediate challenge for effective management in many agricultural areas reliant upon groundwater is that little or no information currently exists on the amount of water extracted for irrigation at the individual farm level. Unlike users of developed surface water, growers who pump groundwater have generally never had to measure or report how much water they extract unless they are located in an adjudicated or actively managed basin.This lack of information on how much water is extracted can become a major handicap for any agency tasked with managing the groundwater supply in the near future, before metering becomes more widespread. Accurate information on extraction amounts and how these amounts can vary from year to year as a function of rainfall conditions will be critical in order RESEARCH ARTICLE Paso Robles vineyard irrigation study provides benchmark data to assist future area groundwater managementResearchers have identified baseline irrigation application data that can help groundwater sustainability agencies estimate regional irrigation usage for wine grape crops. AbstractAccurate information on irrigation water usage does not exist in many areas where groundwater is the primary water source. This lack of information will hinder efforts to manage these groundwater basins sustainably according to current and future water regulations and policies. Using a low-cost methodology of irrigation-line pressure sensors connected to data loggers, we estimated irrigation applications at 84 vineyard sites in the Paso Robles Groundwater Basin over 4 years (2010)(2011)(2012)(2013). We compared irrigation amounts with the preceding winter's rainfall and with the growing season reference evapotranspiration (ET o ). Over the study period, the average annual irrigation application was 11.46 inches (291 millimeters). The average annual application correlated inversely to the preceding winter's rainfall, while the irrigation over the growing season (April-October) correlated directly with the ET o over this same period. This study provides an initial data framework that can be used by groundwater sustainability agencies to help manage groundwater in the Paso Robles area. The methodology also could be utilized in other regions to estimate regional irrigation usage while maintaining anonymity for participants.Lyre 1 1% * Only a portion of the shoots are positioned under the foliage wires, generally on the side of the trellis with lower risk of sunburn.