poster - International Conference of Agricultural Engineering

Simulation of water flow with root water uptake proposed the new
software SWMRUM
Abstrat
Sina Besharat 1 *
1 Water Engineering Department, University of Urmia, Urmia, Iran
* s.besharat@urmia.ac.ir
Soil water simulation models require a description of root water uptake. In this study, water
flow model including proposed model (SWMRUM) software were compared based on field
measurement under the same condition in Lysimeter. Tube-time domain reflectometry (TDR)
was used to measure soil volumetric water content. Root water uptake model includes root
density distribution function, potential transpiration and soil water stress-modified factor. The
root water uptake model was developed, and linked into a soil water dynamic model to
enable simulation of water movement in soil via numerical solution of Richards’s equation.
The outputs from the model are compared against the measured water content data.
Simulated and measured water contents were in excellent agreement. Analysis of residual
errors, differences between measured and simulated values, can be used to evaluate model
performance. These are root mean square error (RMSE), modeling efficiency (EF), and
coefficient of residual mass (CRM). Results show that maximum root water uptake was 0.023
m3m3d-1 at depth 15-25 cm and minimum was 0.003 m3m3d-1 at depth 60 cm.
Key words: Numerical solution, Richards’ equation, Root distribution, SWMRUM software,
Water flow.
1. Introduction
Rooting patterns have traditionally been analyzed by means of root weight density or root
length density. Root length density is often used to characterize the root system. However, it
is a difficult and time-consuming undertaking to measure and determine root length density
distributions accurately, especially in the field, because the distributions change with different
soils, plant species, growing seasons, climate conditions, and others.
There are some investigations on the root morphology of trees, including the spatial
distribution of roots under localized water application (Kjelgren et al. 1985; Meyer and Peck
1985; Roth and Gardner 1985; Sakovich and Post 1986; Clausnitzer and Hopmans 1994).
Information to date on the spatial and temporal distribution of root water and nutrient uptake
is limited, especially for partially wetted soils (Clothier 1989; Kramer and Boyer 1995). Root
water uptake models that can describe spatial and temporal patterns were developed by
Coelho and Or (1996) and Vrugt et al. (2001).
Understanding the physical processes in the soil which govern water and chemical entry into
the root zone, is a necessary step towards developing more efficient and environmentally
sustainable strategies of root zone management. However, it is also important to understand
the biological processes that operate in the root zone to govern subsequent uptake of water
and chemicals by the roots. The movement of soil water, and of any water-borne chemicals,
is frequently a direct result of the action of plant roots. If we are to understand better, and to
model effectively, soil and plant processes we need at least a quantitative means of
describing the process of uptake by the roots (Green and Clothier 1999).
The objectives of this study are to test SWMRUM model used for root water uptake and to
develop such as empirically spatial distribution model of an apple tree roots. This model
established based on the soil properties.