Solute transport by surface runoff from low-angle slopes: theory and application
✍ Scribed by R. S. Walton; R. E. Volker; K. L. Bristow; K. R. J. Smettem
- Publisher
- John Wiley and Sons
- Year
- 2000
- Tongue
- English
- Weight
- 312 KB
- Volume
- 14
- Category
- Article
- ISSN
- 0885-6087
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✦ Synopsis
The removal of chemicals in solution by overland ¯ow from agricultural land has the potential to be a signi®cant source of chemical loss where chemicals are applied to the soil surface, as in zero tillage and surfacemulched farming systems. Currently, we lack detailed understanding of the transfer mechanism between the soil solution and overland ¯ow, particularly under ®eld conditions. A model of solute transfer from soil solution to overland ¯ow was developed. The model is based on the hypothesis that a solute is initially distributed uniformly throughout the soil pore space in a thin layer at the soil surface. A fundamental assumption of the model is that at the time runo commences, any solute at the soil surface that could be transported into the soil with the in®ltrating water will already have been convected away from the area of potential exchange. Solute remaining at the soil surface is therefore not subject to further in®ltration and may be approximated as a layer of tracer on a plane impermeable surface. The model ®tted experimental data very well in all but one trial. The model in its present form focuses on the exchange of solute between the soil solution and surface water after the commencement of runo. Future model development requires the relationship between the mass transfer parameters of the model and the time to runo to be de®ned. This would enable the model to be used for extrapolation beyond the speci®c experimental results of this study. The close agreement between experimental results and model simulations shows that the simple transfer equation proposed in this study has promise for estimating solute loss to surface runo.