A preliminary evaluation of ecohydrological separation in a semi-arid riparian area

In recent years the ecohydrological separation paradigm has stimulated significant scientific debate, as it challenges the basis of existing hydrological process understanding. Through the use of stable isotope analysis several studies have demonstrated that two isotopically distinct water stores may exist within the subsurface, a matric-bound store which sustains transpiration and a mobile store which contributes to the recharge of groundwater and streams. Despite growing evidence supporting this hypothesis, further testing across a range of climatic regimes and environmental settings has been advocated to develop an improved hydrological understand of this paradigm. In this study, the dual isotopic composition of meteoric and environmental waters was analysed in a semi-arid riparian environment during a significant El Nino induced drought, to ascertain if plants were using water that would have otherwise contributed to stream and/or groundwater recharge. Overall, the results of these investigations showed no clear evidence supporting ecohydrological separation. Environmental waters were found to be significantly different from rainfall, whereas no significant differences were established between xylem, bulk soil water, and streamflow. While, these findings represent a unique scenario with regards to the testing of ecohydrological separation, these results are by no means ubiquitous as sampling was conducted during extreme climatic conditions with limited spatio-temporal representation of the system. Therefore, longer-term sampling and monitoring is recommended to obtain an improved understanding of the system under a range of climatic conditions. (C) 2021 European Regional Centre for Ecohydrology of the Polish Academy of Sciences. Published by Elsevier B.V. All rights reserved.