hydraulic performance of water level regulators and off-take structures in zayandeh rud and doroodzan networks

administrative regulations for water flow decrease distribution efficiency and effect the economical operation of irrigation networks. complications in distribution systems and the decrease in availability of water require study of the hydraulic performance of existing flow control structures. control systems designed by neyrpic (zayandeh rud network) and usbr (doroodzan network) were investigated and suitable hydraulic structures were considered. the neyrpic modules and cho gates were used as intakes. amil and avio gates, static weir and sliding gate were chosen as water level regulator structures. the delivered flow rate and energy loss were analyzed for these systems and the nominal and actual flow rates to farmers were compared. energy loss in the flow control structures (xx2, l2, c2, c.h.o, amil, avio, static weir and sliding gates) were measured at different flow rates and compared with allowable loss values calculated using energy loss-flow rate relationships. this analysis combined with the relative error(er) and x2 allowed assessment of the most accurate and suitable system for delivering water from off-takes and water level regulators. a significant difference (p £ 0.05) was found for the flow rate in doroodzan network, but not in the zayandeh rud network. considering these results and the low error values for zayandeh rud network, the xx2, l2, c2 gates are recommended for discharge regulation. amil gates and duckbill weirs are also recommended because of the minimum error and insignificant head loss in these structures.