Simulation of Soil Water Movement in Sandy Soil under a Prairie Field with Hydrus _2D Model
Summary: One of the main characteristics of trickle irrigation system is that water leaving an emitter
enters the soil and moves both laterally and vertically. There has been much speculation on the shape and moisture
distribution within the wetted soil volume. This knowledge is important in the design, operation and management
of a trickle irrigation system. A simulation study of soil water distribution under a prairie field in Tripoli Libya, by
the use of the two dimensional model Hydrus 2D model was carried out. Sandy soil was irrigated using surface
point source with application rates of 1.5, 2, 2.7, 3, 3.5, 4.5, 4.8 and 6 l/h. The surface wetted radius, vertical
advance of wetting front and the distribution of moisture content in the soil profile were determined. Three
statistical criteria were used to compare the quality of simulation results, such as mean bias error (MBE), root
mean square error (RMSE) and Theil’s Inequality coefficient (U). Simulation positions of the wetting front were
in agreement relative to the observed measurements of the wetting front. Specifically, in the lateral, the
experimentally determined wetting front was closely estimated by the model. In the downward direction the
simulated wetting front advanced much slower than the observed especially at later stage of infiltration.
Considering the difficulties in estimating the dynamic water conditions in the field there was generally good
agreement (especially in the lateral direction) between the measured and simulated values. In the deeper
downward direction the simulated moisture content distributions were less than the measured. On the other hand,
the Hydrus_2D model described the water content distribution quite well at relatively high levels of moisture
contents; however, it did not do as well at lower moisture content. The discrepancies between the simulated and
measured values may be due to variation in the size of the surface source of water during infiltration and to the
natural variation of soil properties. However, due to the complex mechanisms of water movement under the
complicated boundary and initial conditions from a surface point source the results support the use of Hydrus 2D
as a tool for investigating and designing point source trickle irrigation system.
Keywords: Trickle irrigation, wetting front, soil moisture distribution, Hydrus _2D model
Ahmed Ibrahim Ekhmaj, M.S.M. Amin, Abdul Hakim Almdny, W. Aimrun, .M. Abdulaziz, (1-2006)
Publisher's website
