Modeling pollutant transport in overland flow over non-planar and non-homogenous infiltrating surfaces

Abstract

Pollutant transport in overland flow over surfaces with spatially varying microtopography, roughness, and infiltration was investigated using the diffusion wave equation and transport rate-based equation. The finite volume method in space and an implicit backward difference scheme in time were employed in the numerical solution of the 2D governing equations. The developed model was first tested against an analytical solution and an experimental study involving overland flow and the associated pollutant transport, subsequently a series of numerical tests were carried out. Non-point source pollution was investigated under spatially varying microtopography, roughness, and infiltration. The simulation results showed that microtopography and roughness were the dominant factors causing significant spatial variations in solute concentration. When the spatially varying microtopography was replaced by a smooth surface, the result was an overestimation of the solute rate at the outlet of the upland. On the other hand, when the spatially varying roughness was replaced by the average roughness and spatially varying infiltration rate by the average infiltration rate, the pollutant discharge at the outlet of the upland was not significantly affected. The numerical results further showed that one cannot ignore the spatial variations of slope and roughness when investigating the local pollutant concentration distribution.

Canonical correlation analysis of hydrological response and soil erosion under moving rainfall

“…The influences of rainfall characteristics on hydrologic responses have been investigated experimentally (de Lima et al, 2009;Ran et al, 2011;2012b;2012c;He et al, 2013), using field investigations (Ran et al, 2011), and through computational modeling (Singh, 2005;Nunes et al, 2006;Ran et al, 2009). Olson and Wischmeier (1963) measured the soil loss per unit of rainfall erosivity based on simulated rainfall and plot experiments, and then scientists led by Wischmeier developed the famous universal soil loss equation (USLE), in which rainfall was considered a major influencing factor impacting overflow (Foster et al, 1977;Wischmeier and Smith, 1978).…”