Depth gradient of saturated hydraulic conductivity by Guelph permeameter method in research farm of agricultural faculty, Razi University, Kermanshah

Hydraulic conductivity (K) is one of the most important parameters in soil sciences, which has highly variation in different direction and depths. Information on spatial and temporal variations of soil hydraulic conductivity is essential to improve soil and water management. The purposes of this study are measuring of the saturated hydraulic conductivity and its depth variation by Guelph permeameter method in the research farm of agricultural faculty, Razi University, Kermanshah. In this regards, 30 boreholes with 8 cm diameter and three depths (60, 90 and 120 cm) were drilled in a grid of 5×5 m. Identification tests such as soil gradation, determination of the liquid and plasticity limits and specific gravity have been done on soil samples and indicated the soil texture was clay. After identification tests, Guelph Permeameter test for three fixed ponding depths of 5, 15 and 25 cm were conducted to determine saturated hydraulic conductivity of soil. The results of statistical analysis showed that hydraulic conductivity values at 60 cm depth have significant difference in 5% level with values about 90 and 120 cm depths and reduction of hydraulic conductivity from 90 to 120 cm was neglected. Between single depth analysis, Laplace’s analysis with 5 cm ponding depth and Richards’s regression basic analysis with 15 cm ponding depth have provided the highest and lowest saturated hydraulic conductivity respectively.