English abstract
This research was conducted to study the factors leading to the uniform distribution of water from a subsurface irrigation system using porous lubes. The factors included the depth at which the tubes are installed, operating pressure, depth of impermeable layer, and a gravel envelope surrounding the tubes. A laboratory soil tank was constructed to determine the effect of these factors. The tank was filled with sand and fitted with porous tubes. The tank and the tubes represent a section of soil profile. The results of this study showed that the depth of the impermeable layer affected significantly the water-table rise in the soil profile. The gravel envelope did not show any advantage over tubes without an envelope in sandy soils. A separate experiment was conducted to compare the characteristics of the flow from the porous tubes with the specifications given by the manufacturer. The results of the experiment showed that porous tubes do not work efficiently either under low pressure (below 80 kPa) or very high pressure (i.e. above 150 kPa).
