Abstract
Abstract. Water infiltration and overland flow are relevant in considering water partition among plant life forms, the sustainability of vegetation and the design of sustainable hydrological models and management. In arid and semi-arid regions, these processes present characteristic trends imposed by the prevailing physical conditions of the upper soil as evolved under water-limited climate. A set of plot-scale field experiments at the semi-arid Patagonian Monte (Argentina) were performed in order to estimate the effect of depression storage areas and infiltration rates on depths, velocities and friction of overland flows. The micro-relief of undisturbed field plots was characterized at z-scale 1 mm through close-range stereo-photogrammetry and geo-statistical tools. The overland flow areas produced by controlled water inflows were video-recorded and the flow velocities were measured with image processing software. Antecedent and post-inflow moisture were measured, and texture, bulk density and physical properties of the upper soil were estimated based on soil core analyses. Field data were used to calibrate a physically-based, mass balanced, time explicit model of infiltration and overland flows. Modelling results reproduced the time series of observed flow areas, velocities and infiltration depths. Estimates of hydrodynamic parameters of overland flow (Reynolds-Froude numbers) are informed. To our knowledge, the study here presented is novel in combining several aspects that previous studies do not address simultaneously: (1) overland flow and infiltration parameters were obtained in undisturbed field conditions; (2) field measurements of overland flow movement were coupled to a detailed analysis of soil microtopography at 1 mm depth scale; (3) the effect of depression storage areas in infiltration rates and depth-velocity friction of overland flows is addressed. Relevance of the results to other similar desert areas is justified by the accompanying biogeography analysis of similarity of the environment where this study was performed with other desert areas of the world.
Highlights
The complexity of interactions between overland flow and infiltration has long received attention in hydrological studies
The study here presented is novel in combining several aspects that previous studies do not address simultaneously: (1) overland flow and infiltration parameters were obtained in undisturbed field conditions; (2) field measurements of overland flow movement were coupled to a detailed analysis of soil microtopography at 1 mm depth scale; (3) the effect of depression storage areas in infiltration rates and depth-velocity friction of overland flows is addressed
A biogeography analysis of the similarity of the experimental site in this study with other areas of the world is included to ease eventual comparisons of the results presented here with those obtained in similar studies
Summary
The complexity of interactions between overland flow and infiltration has long received attention in hydrological studies. Usual procedures to study run-off-infiltration processes involve the use of hydrological models based on hydrograph records. A large body of literature has been devoted to the criteria used to inspect hydrograph records (Ewen, 2011), less attention has been paid to the fact that many hydrological models that can accurately reproduce hydrograph records, produce severely biased estimates of overland flow velocities (Mugler et al, 2011; Legout et al, 2012) or Reynolds-Froude numbers (Tatard et al, 2008). Frictional effects must be accounted for, usually through simplifying equations of the fundamental hydrodynamic laws on continuity and momentum balance involved. To this aim, most field and laboratory studies on overland flow use the Darcy-Weisbach’s f and Manning’s n
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