Partitioning solute transport between infiltration and overland flow under rainfall

Abstract

Solute transport from soil to overland flow is an important source of nonpoint pollution and was investigated through tracer studies in the laboratory and at an outdoor laboratory catchment. The depth of surface water interaction with soil, defined as the mixing zone is a useful value for approximate estimation of potential solute transport into surface water under rainfall. It was measured in the laboratory for a noninfiltration case (0.90 to 1.0 cm) and estimated through mass balance modeling for an infiltration case (0.52 and 0.73 cm). At an outdoor laboratory catchment, mixing zones were calculated through calibration of a numerical model that describes unsteady, uniform, infiltration and chemical transport. Overland flow was simulated using kinematic wave theory. Mixing zone depths ranged from 0.47 to 1.02 cm and were a linear function of rainfall intensity. Also, the fraction of solute present in the mixing zone at the time of ponding which was extracted into overland flow was a linear function of the initial soil moisture content. A steady state analytical approximation of the solute transport model was also developed which overpredicted solute transport into overland flow by 1 to 60%.

Multiresponse modeling of variably saturated flow and isotope tracer transport for a hillslope experiment at the Landscape Evolution Observatory

“…Various hypotheses have been invoked to explain possible factors that affect the migration and distribution of solutes under unsaturated, heterogeneous conditions, including turbulent mixing due to high rainfall (Havis et al, 1992); solute transfer between mobile and immobile water (De Smedt and Wierenga, 1984); mobile-immobile exchange and hysteresis (Butters et al, 1989;Russo et al, 1989aRusso et al, , b, 2014; lateral mixing due to velocity fluctuations (Russo et al, 1998); isotope effects (Barnes and Allison, 1988;LaBolle et al, 2008;Zhang et al, 2009);variable, state-dependent anisotropy (McCord et al, 1991); non-Gaussian early-time mean tracer plume behavior (Naff, 1990); non-Fickian solute migration at low water contents (Padilla et al, 1999) and for macroscopically homogeneous sand (Bromly and Hinz, 2004); and saturation-dependent dispersivity (Raoof and Hassanizadeh, 2013). In addition, Konikow et al (1997) and Parker and van Genuchten (1984) discuss the importance of boundary condition treatment (e.g., water-solute injection, solute exchange between soil and atmosphere).…”

Solute transport by surface runoff from low-angle slopes: theory and application

“…The results of previous research (e.g. Hubbard et al, 1989a,b;Havis et al, 1992) as well as the results of trial 7, site 4 ( Figure 5g) have shown that the shape, as well as the position of the curve, changes with changes in y i . If runo occurs during the early stages of in®ltration then there is potential for a very high initial Br concentration in the runo.…”

“…14, 1139±1158 (2000) where C p is the concentration of the chemical in precipitation (mg l À1 ), C r is the concentration of the chemical in surface water (mg l À1 ), C s is the concentration of the chemical in soil solution (mg l À1 ), f is the in®ltration rate (m s À1 ), q is the¯ow in the x direction per unit width (m 2 s À1 ), R is the rainfall rate (m s À1 ), t is time (s), x is the distance in the direction of horizontal¯ow (m), y is surface water depth (m) and a is the mass transfer coecient (m s À1 ). Equation (4) has similarities with the mass balance equations for the lateral transport of dissolved chemicals by surface runo presented by Havis et al (1992) and Wallach and Shabtai (1992a,b).…”

“…Heathman et al, 1985;Havis et al, 1992). This early commencement of runo was because either in®ltration was restricted or the soil was initially saturated.…”

Kinematic wave solutions for pollutant transport by runoff over an impervious plane, with instantaneous or finite‐period mixing

“…He verified the model using a set of published experimental data and concluded that kinematic wave theory was a promising tool for storm water modelling. Havis et al (1992) partitioned solute transport between infiltration and overland flow under rainfall. They concluded that solute transport from soil to overland flow was an important source of non-point pollution.…”