Modeling the crop transpiration using an optimality-based approach

Abstract

Evapotranspiration constitutes more than 80% of the long-term water balance in Northern China. In this area, crop transpiration due to large areas of agriculture and irrigation is responsible for the majority of evapotranspiration. A model for crop transpiration is therefore essential for estimating the agricultural water consumption and understanding its feedback to the environment. However, most existing hydrological models usually calculate transpiration by relying on parameter calibration against local observations, and do not take into account crop feedback to the ambient environment. This study presents an optimality-based ecohydrology model that couples an ecological hypothesis, the photosynthetic process, stomatal movement, water balance, root water uptake and crop senescence, with the aim of predicting crop characteristics, CO 2 assimilation and water balance based only on given meteorological data. Field experiments were conducted in the Weishan Irrigation District of Northern China to evaluate performance of the model. Agreement between simulation and measurement was achieved for CO 2 assimilation, evapotranspiration and soil moisture content. The vegetation optimality was proven valid for crops and the model was applicable for both C 3 and C 4 plants. Due to the simple scheme of the optimality-based approach as well as its capability for modeling dynamic interactions between crops and the water cycle without prior vegetation information, this methodology is potentially useful to couple with the distributed hydrological model for application at the watershed scale.crop transpiration, CO 2 assimilation, optimality, feedback, ecohydrological model

Overview of Ecohydrological Models and Systems at the Watershed Scale

“…Caylor et al [66] indicated that, in a region with limited water, the optimization mechanism of vegetation-hydrological interaction was to maximize the utilization of water resources and minimize water stress. In addition, Wang et al [67], Pauwels et al [68], and Lei et al [69] carried out related work.…”

Evapotranspiration Over Heterogeneous Vegetated Surfaces

“…However, this is also the most challenging issue in ET studies. Nevertheless, there have been numerous attempts on this issue, such as the thermodynamic entropy theory (Bobylev et al 2001), machine learning approach (Yang et al 2006;Sudheer et al 2002) and ecosystem optimality theory (Lei et al 2008). …”

“…During the past decade, various models have been developed to partition available energy at the soil-plantatmosphere interface and to simulate mass or energy movement in the soil. Examples include those developed by Wilson et al (2003), Lee and Mahrt (2004), Lei et al (2008) and Krobel et al (2010). A common SPAC model usually includes two parts, the below-ground part (soil) and the above-ground part.…”

An experiment to gauge an ungauged catchment: rapid data assessment and eco-hydrological modelling in a data-scarce rural catchment

“…The functional soil map is the result of a RS classification of the same Landsat 7 data; the five functional soil classes and three sub-classes as in Table 1. (Hundecha and Bárdossy 2004), (b) mechanistic representation of the major functionality in the water cycle (Tietjen et al 2009), (c) data-driven look-up table referencing (Güntner and Bronstert 2004), and (d) optimality-based approaches (Lei et al 2008, Schymanski 2008. Jackson et al (2009) underpin the strong link between hydrology and ecology and point out that in agricultural systems this link is very simplified and degrees of freedom are reduced.…”