Impact of climate change on vadose zone processes is still unknown. Preferential flow and transport can be quantitatively important when a large amount of water and nutrients are rapidly moving through the soil profile. Recent analyses at the catchment scale showed a clear relationship between precipitation events >25 mm/day and the occurrence of preferential flow. However, results on spatially-distributed parameters were unclear. Still unknown is also whether preferential flow could change spatially and temporally under an altered climatic regime with a different rainfall distribution, more swell-shrink and longer dry periods leading to hydrophobic soil conditions.

We were using observations from arable soil lysimeters (2012 – 2018) from the SOILCan-lysimeter network. A series of three undisturbed soil monoliths (Haplic Luvisols) were taken from the TERENO-SOILCan test site Dedelow and moved to test sites with contrasting climate conditions (Dedelow, Bad Lauchstädt, Selhausen). Each test site contains a series of three soil profiles, which differ in terms of their erosion history (low, medium, strong) and are equipped with water content measurements in 10 cm, 30 cm and 50 cm soil depth. Using the sensor response times at these three depths (10, 30, and 50 cm) can be classified into one of four classes: (1) non-sequential preferential flow, (2) velocity-based preferential flow, (3) sequential flow, and (4) no response (Germann and Hensel 2006; Graham and Lin 2011). In a next step such classes can be compared with other spatial parameters and lysimeter observations (precipitation intensity, response time in groundwater recharge and solute transport, canopy structure (height; LAI, land use)). Our hypothesis is that changing climatic conditions impact the soil hydraulic properties, the swell-shrink dynamics, and rainfall distribution. Thus, the occurrence of preferential flow increases with drier climate conditions and higher rainfall intensities.

Jannis Groh (Leibniz Centre for agricultural landscape research; E-Mail: jannis.groh@zalf.de)

Horst H. Gerke (Leibniz Centre for agricultural landscape research; E-Mail: gerke@zalf.de)

Markus Weiler (Hydrology, University of Freiburg; E-Mail: markus.weiler@hydrology.uni-freiburg.de )

Data processing and analysis skills are needed (e.g. R-software or Matlab). A basic knowledge about processes and modelling of soil plant atmospheric interactions is a favorable.

Markus Weiler markus.weiler@hydrology.uni-freiburg.de Tel. +49 (0)761 / 203-3530

German or English

Germann, P.F. and D. Hensel. 2006. Poiseuille Flow Geometry Inferred from Velocities of Wetting Fronts in Soils. Vadose Zone Journal 5: 867-876. Graham, C.B. and H.S. Lin. 2011. Controls and Frequency of Preferential Flow Occurrence: A 175-Event Analysis All rights reserved. No part of this periodical may be reproduced or transmitted in any form or by any means, electronic or mechanical, including photocopying, recording, or any information storage and retrieval system, without permission in writing from the publisher. Vadose Zone Journal 10: 816-831.