Study of Variation of Saturated Hydraulic Conductivity with Time

The variation of the saturated hydraulic conductivity with time, as a function of temperature, has been studied involving field measurement at the College of Aboureyhan Research farm. The College of Aboureyhan is a part of the University of Tehran and the above-mentioned farm is located in the lowland of the southeast of Tehran, Iran. For the purposes of this research study it was planned to measure and record the field data in a plot of 18 m2 . The hydraulic conductivity data were measured in 18 test points inside the study area using the inverse auger-hole method. Experiments were carried out from August 16, 2005 to June 14, 2006. The recorded filed data were then used to calculate the saturated hydraulic conductivity data using Excel software. The relationship between soil temperature, water temperature, and also water’s viscosity with hydraulic conductivity, respectively, were determined. The results of the statistical analysis involving SAS software demonstrated that the variation of temperature can considerably affect the saturated hydraulic conductivity values. The results showed that the lowest values of Ks were obtained in the winter when the water, soil, and air temperature were minimal and these values increased when the temperature increased. The effect of the means of daily K values (values measured in each sample date Kd ) and their corresponding soil temperature adjusted values on drain spacing was determined compared with the average of total K values. The maximum over- and underestimation of drain spacing was 19.1 and 23.3%, respectively, for measured values. These estimations were 9 and 16% for adjusted ones. Also, using the average values of K measured in the soil temperature range of 17–23°C resulted in a lower over- or underestimation of drain spacing.