Experimental study of the temporal variation of drain water salinity at different drain depths and spacing in the presence of saline groundwater

Drain depth and spacing are two factors that affect drain water quality by radial flow of underground water. In this study, temporal variations of drain water salinity and groundwater salinity are evaluated using different drain depths and spacing installations. Experiments were performed in a flume of 1.8 m length, 1 m width and 1.2 m height. Drains were installed at 20, 40 and 60 cm depths at 180, 90 and 60 cm spacing. The salinity of the groundwater and the salinity of irrigation water at the study were about 65 and 0.321 dS/m, respectively. Irrigation water deliveries were 0.14, 0.11 and 0.07 l/s. The results show that increasing the drain depth and irrigation water increases the salinity of drain water. Also in all the cases, the trend of drain water salinity tends to decrease with passing of time. However, the leached salt increases with increase in the drain spacing. In addition, drainage water quality decreases with increase in the drain spacing for each drain depth and discharge. On the other hand, the degree of time stability increases with increasing drain spacing. However, it was noticed that faster removal of salt from groundwater can be achieved with increasing drain spacing, depth and discharge.