Class RunoffSurfaceCover
- All Implemented Interfaces:
net.simplace.sim.util.FWSimFieldContainer
This SimComponent calculates the surface cover fraction for runoff and erosion simulations. The algorithm follows the same formulations used in the APSIM (Agricultural Production Systems sIMulator) platform, which was adapted from the PERFECT model (Littleboy et al., 1992).
The soil cover fraction is expressed by the Beer-lambert law as a function of the leaf area index (LAI) and surface organic matter. Both variables can be obtained from a crop growth SimComponent (e.g., LintulBiomass) or prescribed in a management component. The calculation procedure for determining the surface cover fraction is described in the following equations:
\[ \begin{eqnarray} Cover_{Green} & = & 1 - e^{(-K_{Green} \cdot LAI_{Green})} \\ Cover_{Senes} & = & 1 - e^{(-K_{Senes} \cdot LAI_{Senes})} \\ Cover_{SurfOM} & = & 1 - e^{(-K_{SurfOM} \cdot LAI_{SurfOM})} \\ Cover_{Total} & = & 1 - [(1 - Cover_{Green}) \cdot (1 - Cover_{Senes})] \cdot CanHFac \\ CoverFraction & = & 1 - [(1 - Cover_{Total}) \cdot (1 - Cover_{SurfOM})] \\ \end{eqnarray} \]Where LAIGreen (iGreenLAI) is the green LAI (m2/m2); LAISenes (iSenesLAI) is the dry LAI still attached to the crop stems (m2/m2); SurfOM (iSurfOM) is the soil surface residues (t/ha); KGreen (cGreenK), KSenes (cSenesK), and KSurfOM (cSurfOMK) are the extinction coefficients for green LAI, for senesced LAI and SurfOM, respectively (all dimensionless); CoverGreen, CoverSenes and CoverSurfOM are the respective calculated cover fractions; CoverTotal is the total cover fraction of the canopy corrected by crop height; CanHFac is the correction factor (0-1) of CoverTotal as a function of canopy height (iHeight); CoverFraction (CoverFrac) is the final soil cover fraction (0-1) taking into account the crop canopy and soil surface residues. The CanHFac is calculated using an interpolation table consisting of canopy height (cCanopyFactorsHeight) and the respective reducing factors (cCanopyFactors). The effect of height is typically neglected (e.g., CanHFac=1) when the crop height is below 60 cm.
References
APSIM v7.1 source code. Last time accessed: Dec-14-2022. URL: https://github.com/APSIMInitiative/APSIMClassic
Littleboy, M., D.M. Silburn, D.M. Freebairn, D.R. Woodruff, G.L. Hammer, and J.K. Leslie. 1992. Impact of soil erosion on production in cropping systems. I. Development and validation of a simulation model. Aust. J. Soil Res. 30, 757-774.
Holzworth, Dean P., Neil I. Huth, Peter G. deVoil, Eric J. Zurcher, Neville I. Herrmann, Greg McLean, Karine Chenu, et al. “APSIM – Evolution towards a New Generation of Agricultural Systems Simulation.” Environmental Modelling & Software 62 (December 2014): 327–350. https://doi.org/10.1016/j.envsoft.2014.07.009