Document Type : Research Paper

Authors

• Mina Shakiba ¹
• Abdolmajid Liaghat ²
• Farhad Mirzaei ³

¹ M Sc. Graduated of Irrigation Eng., University of Tehran;

² Professor, University of Tehran

³ Assistant Professor, University of Tehran;

Abstract

Effluent disposal and its harmful impacts on environment are an important challenge in drainage projects and environmental problems in Iran. Therefore, by analyzing the flow net and determining the flow paths, efforts must be made to reduce the amount of effluent and improve its quality. This study aimed to observe the mixing depth as an effective parameter affecting the salinity of effluent. In this experiment, a plaxiglass model was used to investigate the effect of water table head on mixing depth. Mixing depth is the  farthermost flow line below the drainage pipe installation depth. At first, KMnO₄ and NaCl were added to groundwater supply to increase the salinity of groundwater to 20 dS/m. Then, by using different input discharge and water table head, the variety of mixing depths was determined with photography. Results showed that with increase in the amount of irrigation water, the water table head and mixing depth increased and caused high salinity of the effluent. For instance, by increasing water table head from 8 cm to 23 cm, salinity of the drainage water raised about 80 percent. Finally, the mixing depth was determined as a function of outflow discharge, hydraulic conductivity, depth of impervious layer, and head in the middle of the drainage water. In the next step, the model was validated using observed experimental field data collected from sugar beet development projects in Amirkabir unit located in Khuzestan, Iran. The comparison was done between the salinity that was simulated by the model and the measured value. The results showed the effect of mixing depth on salinity of effluent. 

Keywords

• Environment
• Salinity of effluent
• Water table head