THE STUDY OF PERMEABILITY OF SUB-SURFACE IRRIGATION POROUS CLAY PIPES UNDER WARER QUALITY AND SOIL TEXTURE POINT SOURCE

The clay pipe sub-surface irrigation has been considered due to reduced evaporation from the soil surface and effective use of water in arid and semi-arid regions such as Iran. Due to the ambiguous dimensions of this method of irrigation in different soil texture a two-year study was conducted aimed to investigate the effect of two water qualities with electrical conductivity of 0.346 87 and 3.78 dS/m on emission of clay pipes respectively, under laboratory and field conditions with three types of clay loam, sandy loam and loamy texture at two meters hydrostatic pressure. The laboratory results of emission measurements resulted in a multivariate model for predicting long-term final pipe emission. Also, water salinity significantly changed the parameters of the equation, hence confirming the effect of salinity on pipe emission reduced. The field results of pipe emission were significantly affected by two water qualities. The significant point in this study is the significant reduction in initial emission in saline water use compared to low salinity water. On the other hand, a mathematical regression relationship was found with high correlation between initial and final pipe emission in both water qualities under field conditions for total water volume. Also, the emission reduction rate over time was identical in pipe with different emission follows the regression model with high coefficient of determination in laboratory and field. The study of emission of clay pipes in laboratory and field showed the susceptibility of these pipes to reduced emission even in low salinity water use, even showed that the amount of pipes in the long run will be significantly reduced, which should be replaced according to the salinity of water, irrigation and soil type.