Experimental Study of Drainage Water Salinity Changes at Intervals and Various Depths of Drain in the Presence of Saline Groundwater

The purpose of this study was to determine the trend of agricultural drainage water salinity changes in outflow of the different spacings and depths, during the study time periods. In this research, an experimental box model was used with dimensions of 1.8×1×1.2 meters. The Drains at the depths of 20, 40 and 60 cm and spacings of 180, 90 and 60 cm, were installed in the box model and examined for the discharges of 0.14, 0.11 and 0.07 lit/sec. Groundwater and irrigation water salinities were chosen as 65 and 0.32 dS m-1, respectively. The results showed that in all drains the outflow water salinity was changed with time in a decreasing trend. With increasing the drains spacing, the amount of output water salinity increased and this increased the time to reach balance. The results showed that when the spacing, depth and discharge flow rate of drains were decreased, the effect of ground water on drain water was decreased.