TY - JOUR

T1 - Specific processes during in situ infiltration into a sandy soil with low-level water repellency

AU - Ganz, Christina

AU - Bachmann, Jörg

AU - Lamparter, Axel

AU - Woche, Susanne K.

AU - Duijnisveld, Wilhelmus H.M.

AU - Göbel, Marc O.

N1 - Copyright: Copyright 2013 Elsevier B.V., All rights reserved.

PY - 2013/3/25

Y1 - 2013/3/25

N2 - Despite growing knowledge about water repellent soils it is not well investigated how soil water repellency (SWR) of a lower level influences the in situ water infiltration into soils. Hence, we investigated a sandy soil where we found subcritical water repellency and unexpected stable (persistent) contact angles (CAs) in the subsoil characterized by CA measurements in the laboratory. To characterize the influence of this persistence on in situ water infiltration, a ponded tracer infiltration experiment was carried out. During the infiltration, hydraulic sensors revealed a slight saturation at the wetting front which is a sign for unstable flow. The excavated dye-stained infiltration zone was conical and its lateral extent decreased with increasing depth, showing characteristics of a macro-finger. We suggest the subsoil to exhibit a strong hysteretic water retention characteristic governing the infiltration process, but we could not verify this by standard laboratory measurements, as strongly persistent SWR prevented the fast wetting of the soil samples. Close to saturation the persistence of SWR led to a wetting period of soil samples of at least 56. days to overcome SWR and reaching an equilibrium state. There are three major conclusions of this study: 1. In contrast to many other studies we found persistent SWR also in the subsoil and not only in the humic topsoil, 2. The shape of the wetting front is contrary to common expectations for homogeneous sandy soils and 3. The wettability characteristics found might also be relevant for assessing infiltration dynamics at other sites regarding the fact that those observations are not obvious.

AB - Despite growing knowledge about water repellent soils it is not well investigated how soil water repellency (SWR) of a lower level influences the in situ water infiltration into soils. Hence, we investigated a sandy soil where we found subcritical water repellency and unexpected stable (persistent) contact angles (CAs) in the subsoil characterized by CA measurements in the laboratory. To characterize the influence of this persistence on in situ water infiltration, a ponded tracer infiltration experiment was carried out. During the infiltration, hydraulic sensors revealed a slight saturation at the wetting front which is a sign for unstable flow. The excavated dye-stained infiltration zone was conical and its lateral extent decreased with increasing depth, showing characteristics of a macro-finger. We suggest the subsoil to exhibit a strong hysteretic water retention characteristic governing the infiltration process, but we could not verify this by standard laboratory measurements, as strongly persistent SWR prevented the fast wetting of the soil samples. Close to saturation the persistence of SWR led to a wetting period of soil samples of at least 56. days to overcome SWR and reaching an equilibrium state. There are three major conclusions of this study: 1. In contrast to many other studies we found persistent SWR also in the subsoil and not only in the humic topsoil, 2. The shape of the wetting front is contrary to common expectations for homogeneous sandy soils and 3. The wettability characteristics found might also be relevant for assessing infiltration dynamics at other sites regarding the fact that those observations are not obvious.

KW - Macro-finger

KW - Ponded infiltration

KW - Stable contact angles

KW - Unstable flow

KW - Water repellency

UR - http://www.scopus.com/inward/record.url?scp=84875397552&partnerID=8YFLogxK

U2 - 10.1016/j.jhydrol.2013.01.009

DO - 10.1016/j.jhydrol.2013.01.009

M3 - Article

AN - SCOPUS:84875397552

VL - 484

SP - 45

EP - 54

JO - Journal of hydrology

JF - Journal of hydrology

SN - 0022-1694

ER -