Evaluation of a distributed parameter ecohydrological model (TOPOG-IRM) on a small cropping rotation catchment
1997
Dawes, W.R. | Zhang, L. | Hatton, T.J. | Reece, P.H. | Beale, G.T.H. | Packer, I.
A biophysically based distributed parameter ecohydrological catchment model TOPOG IRM, is described which predicts the dynamic interactions between soil-vegetation-atmosphere systems over a catchment. The physiological control on transpiration is formulated using canopy resistance defined as a function of the net assimilation rate, the relative humidity and CO2 concentration at the leaf surface. Rainfall infiltration, runoff and redistribution are simulated with the Richards equation and evapotranspiration is calculated using the Penman-Monteith equation. Two innovative features of the model are (1) coupling of the vegetation-atmosphere system by changing the value of the vapour pressure deficit of air in the canopy, and (2) the plant carbon balance, which allows the simulation of plant growth using a saturation rate kinetics formulation The model was validated using evapotranspiration. soil moisture and leaf area index measurements from Wagga Wagga, N.S.W., Australia, for a period of 1992-1993. The calculated evapotranspiration was in good agreement with the observations. The soil moisture content at various depths was well simulated for two typical sites. The model also reasonably reproduced leaf area index of wheat and canola for two growing seasons. The success of the model simulations was due to the reasonably realistic treatment of the soil and canopy processes. The sensitivity analysis indicated that (1) the maximum assimilation rate of carbon affects canopy transpiration significantly, and (2) the total drainage is sensitive to the lower boundary conditions and the saturated hydraulic conductivity. TOPOG IRM is a valuable tool in studying catchment responses under different land management practices. However, the application of the model is limited by the large amount of data required regarding soil and vegetation properties, and their spatial distribution.
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