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Root zone salinity and sodicity under seasonal rainfall due to feedback of decreasing hydraulic conductivity
Author(s) -
van der Zee S. E. A. T. M.,
Shah S. H. H.,
Vervoort R. W.
Publication year - 2014
Publication title -
water resources research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.863
H-Index - 217
eISSN - 1944-7973
pISSN - 0043-1397
DOI - 10.1002/2013wr015208
Subject(s) - dns root zone , hydraulic conductivity , salinity , environmental science , soil science , leaching (pedology) , drainage , soil salinity , groundwater , soil water , hydrology (agriculture) , geology , ecology , geotechnical engineering , oceanography , biology
Abstract Soil sodicity, where the soil cation exchange complex is occupied for a significant fraction by Na + , may lead to vulnerability to soil structure deterioration. With a root zone flow and salt transport model, we modeled the feedback effects of salt concentration ( C ) and exchangeable sodium percentage ( ESP ) on saturated hydraulic conductivity K s ( C , ESP ) for different groundwater depths and climates, using the functional approach of McNeal (1968). We assume that a decrease of K s is practically irreversible at a time scale of decades. Representing climate with a Poisson rainfall process, the feedback hardly affects salt and sodium accumulation compared with the case that feedback is ignored. However, if salinity decreases, the much more buffered ESP stays at elevated values, while K s decreases. This situation may develop if rainfall has a seasonal pattern where drought periods with accumulation of salts in the root zone alternate with wet rainfall periods in which salts are leached. Feedback that affects both drainage/leaching and capillary upward flow from groundwater, or only drainage, leads to opposing effects. If both fluxes are affected by sodicity‐induced degradation, this leads to reduced salinity ( C ) and sodicity ( ESP ), which suggests that the system dynamics and feedback oppose further degradation. Experiences in the field point in the same direction.