Evaluation of Subsurface Drainage System in Unsteady FlowConditions (Case Study: Research Farm of Shahid ChamranUniversity of Ahvaz, Iran)

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IRRIGATION02_118

تاریخ نمایه سازی: 20 شهریور 1401

Abstract:

Karoon River is one of the most important water resources for irrigation of farming lands in Khuzestan,Iran, which its quality has decreased in early years. Due to increases in water tables and salts in soilsusing Karoon River for irrigation, a subsurface drainage system was installed at an agricultural researchfarm at Shahid Chamran University of Ahvaz to overcome these problems. The research farm containedseven laterals (diameter ۱۲۵ mm, length ۲۰۰ m, spacing ۳۰ m, and depth ۱.۵ m) and one collector(diameter ۳۰۰ mm). This study was conducted on this farm to evaluate above mentioned drainage system.To this end, (including outlet discharge from laterals and collector, outlet salinity from laterals andcollector, salinity changes before (B) and after (A) irrigation), relative groundwater depth (RGWD), saltexport indicator (SEI), and relative electric conductivity (REC) during three irrigation periods weredetermined. The result showed irrigation increased the drainage rate greatly. But it is notable this trenddecreased after ۵۲ hours. The drainage water salinity fluctuated during this study while high salinity wasfound in the first irrigation. The results also showed that drainage water salinity of the collector wasnearly constant, so the maximum salinity, determined during second irrigation, was only ۱.۰۴ and ۱.۰۳times more than maximum drainage salinity during first and third irrigations, respectively. Soil salinitydecreased after irrigation but it was increased after several days due to capillary rise. RGWD was in therange of ۰.۹-۱.۱ and showed that the drainage system had sufficient efficiency for the control water table.In addition, SEI, for each irrigation period was in the standard value but maximum SEI was obtainedduring third irrigation and it was ۱.۲۷ and ۱.۴۲ times more than first and second irrigations, respectively.Maximum REC was determined for a distance approximately ۱۵۰ m from collector before irrigationwhich this index was ۱.۲۸ and ۱.۲۶ times less than distance ۱۰۰ and ۵۰ meters, respectively. According tothe results, the installation of the drainage network had a good performance to control the water table andsoil salinity.

Authors

Soroush Mehrabian

Ph.D, Irrigation and Drainage, Shahid Chamran University of Ahvaz, Ahvaz, Iran

Abd Ali Naseri

Professor of irrigation and drainage engineering, Shahid Chamran University of Ahvaz, Ahvaz, Iran

Abdorrahim Hooshmand

Associate professor of irrigation and drainage engineering, Shahid Chamran University of Ahvaz,Ahvaz, Iran

Mohsen Ahmadee

Lorestan Agricultural and Natural Resources Research Center, AREEO, Khorramabad, Iran