IRRIGATION PATTERN IN IMPROVED BRANCH CANALS

The objective of this study is to verify the actual irrigation pattern in improved distributary canals which are operated under continuous flow. The study was applied in Dakalt canal, which is an improved canal in Mit Yazid command area. The study analysed water levels at different locations of the canal for six seasons from summer 2005 to winter 2007/2008. In addition, the study analysed the intensive collected water levels, actual supply discharges, actual withdrawal discharges during two field experiments which were conducted during winter 2006/2007 and summer 2007. The results illustrated the filling and the emptying periods in the canal during the day and the influence of the change in withdraw density on the fluctuation of water levels. The study showed that the irrigation hours were between 6:00 am and 7:00 pm during summer season and between 8:00 am to 7:00 pm for most of the reaches during winter season. During some summer periods, and when withdraw was continuing during the whole day, the withdraw ratios from 7:00 am to 7:00 pm were about 81.7 % and 80.5 % of total withdrawal volumes in the first and the second reaches respectively. The study also showed that average actual water levels were below the design water levels for most of the time during summer season due to the overcrowding of irrigations. Low water levels may make farmers dissatisfied and always complainant especially at end reaches. Supply discharge values were not allocated by equitable manner along the canal reaches and this is likely because there was no internal rotation between lifting points. The current study helps achieving the required design water levels in the next phases of the improvement project by applying internal rotations between single point lifting stations on the canal and its sub branches based on actual pattern of irrigation, which was illustrated in this study. That will enhance operation of improved canals and maximize the benefits of canal improvements.