Biomechanics of Surface Runoff and Soil Water Percolation.
Abstract
In this study, the complex interaction of surface runoff with the biomechanics of soil water transport and heat transfer rate is theoretically investigated using math- ematical model that rely on the two phase flows of an incompressible Newtonian fluid (stormwater) within the soil (porous medium) and on the soil surface (runoff).
The flow and heat transfer characteristics within the soil are determined numerically based on Darcy-Brinkman-Forchheimer model for porous medium coupled with ap- propriate energy equation while analytical approach is employed to tackle the model for interacting surface runoff stormwater.
The effects of various embedded biophys- ical parameters on the temperature distribution and water transport in soils and across the surface runoff together with soil-runoff interface skin friction and Nusselt number are display graphically and discussed quantitatively.
It is found that an in- crease in surface runoff over tightly packed soil lessens stormwater percolation rate but enhances both soil erosion and heat transfer rate.
Introduction
Background Of Study
Surface runoff and soil water percolation are closely associated with rainfall and melting of snow, or glaciers.
Soil inability to absorb excess stormwater and melt- water due to heavy rainfall, high melt rate of snow and glacier, soil saturation, im- pervious resulting from surface sealing or pavement, etc., do lead to surface runoff .
Surface runoff is the major cause of soil erosion and surface water pollution. In urban areas, runoff is the main cause of flooding which may damage properties and infrastructures including loss of life.
In order to alleviate the unpleasant effects of surface runoff, several proactive measures are needed to boost soil absorption of stormwater and meltwater.
These measures may include minimizing impervi- ous surfaces in urban areas, adopting soil erosion and flood control programs, etc.
Moreover, percolation describes the downward flow rate of the stormwater or melt- water within the soil .
Water percolation in the soil contributes to the formation of groundwater aquifers which serves as a freshwater storage that can be utilized dur- ing droughts when surface water supplies are reduced.
Generally, soil is regarded as a porous media; the soil loose sediments like sand and gravel are porous and perme- able. It can hold water and allows water to flow through.
While the amount of porosity in a soil depends on its mineral content and structure, the rate of water per- colation depends on soil permeability (i.e. the size of the soil pore spaces and how the pores are connected).
For instance, sandy soils have large well connected pores and higher permeability than the clay soils.
The use of mathematical models to tackle the menace of surface runoff and enhance the soil water percolation for the formation of groundwater aquifers has attracted the attention of several scientists and researchers .
References
Xuezhi Tan Xia Yang Wenquan Gu Haoxin Li Baoli Xu Dongguo Shao. “Eval- uation of soil water percolation under different irrigation practices, antecedent moisture and groundwater depths in paddy fields”. In: Agricultural Water Man- agement 192 (2017), pp. 149–158.
HC Brinkman. “A calculation of the viscous force exerted by a flowing fluid on a dense swarm of particles”. In: Flow, Turbulence and Combustion 1 (1949), pp. 27–34.
Keith L Bristow and R “Modeling the impact of partial surface mulch on soil heat and water flow”. In: Theoretical and applied climatology 54.1-2 (1996), pp. 85–98.
T Chinyoka and OD “Analysis of non-Newtonian flow with reacting species in a channel filled with a saturated porous medium”. In: Journal of Petroleum Science and Engineering 121 (2014), pp. 1–8.
L. Heitman T. S. Ren D. D. Davis R. Horton. “An experimental study of coupled heat and water transfer in wettable and artificially hydrophobized soils”. In: Soil Sci. Soc. Am. J. 78.1 (2014), pp. 125–132.
MichaelaDanácˇová, Peter Valent, and Roman Vy` “Evaluation of Surface Runoff Generation Processes Using a Rainfall Simulator: A Small Scale Labo- ratory Experiment”. In: IOP Conference Series: Earth and Environmental Science. Vol. 95. 2. IOP Publishing. 2017, 022016(1–8).