Using advanced well monitoring and manipulation technology to improve irrigation water salinity in California?s central coast grape growing region

California grape growers currently face the problem of deteriorating irrigation water quality due to high salinity levels. Saline irrigation water reduces soil quality and leads to reductions in grapevine growth and yield. In agricultural systems, salinity can enter irrigation systems through asymmetrical patterns of groundwater well recharge, where certain layers of the vertical well profile contribute disproportionately to overall irrigation water salinity. Advanced well sampling techniques identifying these vertical and asymmetrical patterns of contamination within wells and can provide users with data needed to minimize withdrawal from contaminated layers of the profile. In the original grant, we proposed to address the following short term goals: 1) to profile problematic wells to identify source layers of salinity contamination; and 2) to evaluate the effectiveness of well patching in reducing overall irrigation water salinity. We achieved both goals within the one year funding period. Our results from three wells sampled in August 2009 indicate that constituent contribution into each well is fairly uniform throughout each well profile and in most cases was proportional to the overall flow entering the well at each depth. There were few defined layers of high contaminant contribution, and when they did occur the flow contribution at that depth was low causing little effect on the overall concentration measured at discharge. Each well was theoretically analyzed based upon each constituent?s percent contribution to the overall well water quality. Findings from this theoretical analysis of the effects of a well modification at a given depth within each well confirmed the constituent profile data indicating that a modification in any of these wells would be ineffective due to the lack of a defined contamination zone.