Simulation and validation of concentrated subsurface lateral flow paths in an agricultural landscape

Abstract

Abstract. The importance of soil water flow paths to the transport of nutrients and contaminants has long been recognized. However, effective means of detecting concentrated subsurface flow paths in a large landscape are still lacking. The flow direction and accumulation algorithm based on single-direction flow algorithm (D8) in GIS hydrologic modeling is a cost-effective way to simulate potential concentrated flow paths over a large area once relevant data are collected. This study tested the D8 algorithm for simulating concentrated lateral flow paths at three interfaces in soil profiles in a 19.5-ha agricultural landscape in central Pennsylvania, USA. These interfaces were (1) the interface between surface plowed layers of Ap1 and Ap2 horizons, (2) the interface with subsoil water-restricting clay layer where clay content increased to over 40%, and (3) the soil-bedrock interface. The simulated flow paths were validated through soil hydrologic monitoring, geophysical surveys, and observable soil morphological features. The results confirmed that concentrated subsurface lateral flow occurred at the interfaces with the clay layer and the underlying bedrock. At these two interfaces, the soils on the simulated flow paths were closer to saturation and showed more temporally unstable moisture dynamics than those off the simulated flow paths. Apparent electrical conductivity in the soil on the simulated flow paths was elevated and temporally unstable as compared to those outside the simulated paths. The soil cores collected from the simulated flow paths showed significantly higher Mn content at these interfaces than those away from the simulated paths. These results suggest that (1) the D8 algorithm is useful in simulating possible concentrated subsurface latCorrespondence to: H. S. Lin (henrylin@psu.edu) eral flow paths if used with appropriate threshold value of contributing area and sufficiently detailed digital elevation model (DEM); (2) repeated electromagnetic surveys can reflect the temporal change of soil water storage and thus is a useful indicator of possible subsurface flow path over a large area; and (3) observable Mn distribution in soil profiles can be used as a simple indicator of water flow paths in soils and over the landscape; however, it does require sufficient soil sampling (by excavation or augering) to possibly infer landscape-scale subsurface flow paths. In areas where subsurface interface topography varies similarly with surface topography, surface DEM can be used to simulate potential subsurface lateral flow path reasonably so the cost associated with obtaining depth to subsurface water-restricting layer can be minimized.

Effect of topography and soil parameterisation representing soil thicknesses on shallow landslide modelling

“…This means that the analysis of flow paths using the D-infinity method by Tarboton (1997) may affect flow path simulation results. For example, Zhu and Lin (2009) studied the relationship between a subsurface interface DEM and a land surface DEM using a hydrologic model and reported that result of flow paths in the hydrologic modelling had almost similar results with more than 90% agreement. They then interpreted the distinction between the results of the GSTO and BSTO.…”

Denitrification and Nitrous Oxide Emissions in Annual Croplands, Perennial Grass Buffers, and Restored Perennial Grasslands

“…tersheds (which are not tilled) likely promote lateral hydrological flow paths (Zhu and Lin, 2009), and lateral flow can promote NO 3 − -N transport downslope . The coincident decrease in groundwater levels and NO 3 − -N concentrations from upslope to toeslope wells in the PFS suggests PFS create a NO 3 − -N sink during lateral flow through these systems.…”

Subsurface lateral flow from hillslope and its contribution to nitrate loading in streams through an agricultural catchment during subtropical rainstorm events

“…Subsurface lateral flow from hillslopes and its connectivity to stream flow have been studied by monitoring the dynamics of soil moisture profiles along slopes (Lin, 2006;McNamara et al, 2005;Zhu and Lin, 2009) or trench flow below hillslopes (Newman et al, 1998;Tromp-van Meerveld and McDonnell, 2006;van Verseveld et al, 2009) or both of them (Burke and Kasahara, 2011).…”