The American Geophysical Union (AGU) has selected Dr. Ofer Dahan’s manuscript Amiaz, Y., S. Sorek, Y. Enzel, and O. Dahan “Solute-transport in the Vadose Zone and Groundwater during Flash Floods,” which was published in Water Resources Research in October to be one of its “Research Spotlights”.
Water Resources Research is published by AGU. The paper will also be included in an Eos column, which will appear on the back page of the newspaper. Eos Spotlights include basic graphics and are meant to represent a conversational snapshot of research in a magazine-type format.
“For people living in arid ecosystems, groundwater replenished during seasonal flooding is typically their most important source of freshwater. Yet these same floods may also be responsible for temporarily increasing the salinity of the vital freshwater stores, a relationship shown for the austral summer flooding of the Kuiseb River in Namibia. Between 2006 and 2008, Amiaz et al. (2011) recorded the effect of 12 floods on soil water storage, groundwater electrical conductivity (a measure of salinity), and solute movement throughout various layers of the subsurface along the river. The researchers' primary concern was understanding how soluble salts residing in the vadose zone, the subsurface layer that lies between the groundwater table and the surface, make their way into the aquifer. Through in-field measurements and laboratory soil column experiments, the authors found that as floodwater travels along the surface it triggers a compression wave that moves down through the sandy sediments that compose the channel bed, destabilizing salts in the vadose zone and pushing them into the groundwater. As the floodwater itself percolates through the subsurface, additional salts dissolve into it, further increasing groundwater salinity. The authors noticed that while the first flood of the season leads to the largest leap in groundwater salinity, subsequent flooding can draw even more salt out of the vadose zone due to the rising water table and the subsequent saturation of the vadose zone sediments. They note that it is only upon the arrival of substantial floodwater to the groundwater stores that dilution can compensate for the increased salinity,” according to the Water Research Resources website.
Dr. Dahan is a member of the Zuckerberg Institute for Water Research, which is part of the Jacob Blaustein Institutes for Desert Research.
The study was partially funded by the sixth Framework of the European Commission through the WADE project (FloodWater Recharge of Alluvial Aquifers in Dryland Environments, contract no. GOCE-CT-2003-506680), and by the U.S.-Israel Cooperative Development Research Program, Bureau for Economic Growth, Agriculture, and Trade, U.S. Agency for International Development (grant C24-026).