Applied Engineering in Agriculture Vol. 28(5): 657-664 2012 American Society of Agricultural and Biological Engineers ISSN 0883-8542 657 EVALUATING THE POTENTIAL OF WELL PROFILING TECHNOLOGY TO LIMIT IRRIGATION WATER SALINITY IN CALIFORNIA VINEYARDS C. M. Manuck, N. Heller, M. C. Battany, A. Perry, A. J. McElrone ABSTRACT. Grape growers in some regions of California are confronting problems with soil salinity. Improving irrigation water quality at the source well offers a potential solution to mitigate soil salinity issues in vineyards. Here, we utilized tracer-pulse technology and chemical analysis to assess flow and constituent contributions at various points throughout the depth profiles of three wells with known salinity problems. At the surface, all three wells had several chemical constituents measuring at concentrations higher than the recommended threshold for grapevines. Theoretical well manipulation effects were calculated to evaluate whether blocking inflow at each layer of each well’s depth profile would improve overall water quality at the surface. The profiling technology effectively measured variation in flow and chemical contributions along each profile. As no strong chemical hotspots were detected and the distributions were relatively uniform/symmetric across each of the depth profiles, the theoretical well manipulation offered little improvement in overall well water quality without detrimental effects on volume pumping capacity. For example, in one well a manipulation inserted at 73- to 113-m below ground surface would reduce the overall concentration of several constituents of concern, but would be accompanied by a 41% reduction in well flow. While a well manipulation would have minimal effect for the three wells assessed in this study, this method could be an effective means of improving irrigation water quality for wells with stronger asymmetrical patterns of constituent contributions. Keywords. Well monitoring, Water quality, Tracer-pulse, Grapevines. n dry growing regions, soil salinization is a serious problem confronting sustainable production of irrigated crops. The United Nations Food and Agriculture Organization has estimated that each year 0.25 to 0.5 million ha of irrigated arable land are seriously damaged and lost from crop production due to salt accumulation in soils (FAO, 2002). Saline irrigation water, low rainfall, shifting water tables, and high evapotranspira- tion rates can all contribute to concentrating salts in crop root zones (Tregeagle et al., 2006). In some regions, soil salinization is likely to worsen under the increasing drought frequency predicted by climate change scenarios. Soil salinity is an emerging problem for some major grape growing regions of California (Battany, 2007; 2008). Poor irrigation water quality, limited winter rainfall, and drip/deficit irrigation strategies, which are commonly used to improve vineyard water use efficiency and fruit quality, are contributing to this problem in vineyards (Battany, 2007; 2008). When exposed to salinity, grapevines exhibit reduced photosynthesis and shoot elongation, sodium (Na) and chloride (Cl) toxicity in leaves, and sodium-potassium (K) imbalance (Walker et al., 1981; Garcia and Charbaji, 1993; Fisarakis et al., 2001; Shani and Ben-Gal, 2005). Since Vitis vinifera grapevines have been classified as moderately sensitive to salinity (Maas, 1990) and have only a modest capacity to exclude Cl ions, improving irrigation water quality prior to application could serve as an alternative strategy to avoid soil salinity issues in vineyards. Discrete layers of a vertical well profile can often contribute disproportionately to chemical constituent concentrations of the bulk water extracted at the surface. Asymmetrical patterns of water quality can form as a consequence of vadose zone thickness, seasonal recharge, well depth, aquifer contamination, land use, and geology (e.g. chemical composition of parent rock) (Nightingale and Bianchi, 1980; Spalding and Exner, 1980; Beke et al., 1993; Hudak, 2001). Advanced well sampling techniques can identify vertical and asymmetrical patterns within wells, and a manipulation (e.g. a hydraulic manipulator or well patch) can then be used to minimize water extraction from problematic layers (Heller, 2008). Insertion of an inflatable packer over the screen section producing the asymmetry is a remediation technique which is commonly used for well zone isolation (Swanson, 1986). Eccles et al. (1976) were able to effectively reduce the dissolved nitrate Submitted for review in December 2011 as manuscript number SW 9572; approved for publication by the Soil & Water Division of ASABE in June 2012. The authors are Christine M. Manuck, Biological Research Technician, U.S. Department of Agriculture-Agricultural Research Service, Davis, California; Noah Heller, President, BESST Inc., San Rafael, California; Mark C. Battany, Viticulture Farm Advisor, San Luis Obispo County Cooperative Extension, San Luis Obispo, California; Anji Perry, Viticulturalist, J.Lohr Vineyards & Wines, Paso Robles, California; and Andrew J. McElrone, Research Plant Physiologist, U.S. Department of Agriculture, Agricultural Research Service, University of California, Davis, California. Corresponding author: Andrew J. McElrone, U.S. Department of Agriculture, Agricultural Research Service, 2154 RMI North, University of California, Davis, CA 95161; phone: 530-754-9763; e-mail: ajmcelrone@ucdavis.edu. I