Abstract:
Reliability of water releases is of essential importance, as it is the
basis of water delivery scheduling as well as water resources
planning and management. This study was conducted in Abu
Ushar head regulator of Gezira Main Canal, Gezira Scheme (GS)
at 169 Km from Sennar Dam. The main objective was to study
reliability of water releases downstream Abu Ushar head
regulator. This regulator serves irrigation water operation of the
North GS. It consists of a number of canals namely Turabi,
North West Branch, Abu Ushar Major, Debaba Major, Baranco
Minor, Tatai Minor, Wad Elmagdi Minor and Abu Ushar Scape.
The field work was conducted by measuring water levels during
the period from 1st Oct. to 31th Dec. 2005 at the control structures
of the canals under study. Also, the openings of the gates and the
heads over weirs were daily measured to calculate the discharges
passing through the investigated canals by using the
corresponding equations. The study showed that the average
difference between the recorded discharge (QR) and the
calculated discharge (QC) was (0.4%) for Turabi, and (0.1%) for
North West Branch. The small differences between calculated
and recorded discharges were attributed to the adoption of
appropriate discharge equations by the irrigation authority. This
is also valid for Abu Ushar (4.6%) and Debaba (4.4%) majors. It
was found out that there was disagreement between the recorded
and measured discharges in the case of the minor canals. The
study gave differences in order of 25.6%, 23.6% and 16.7% for
Baranco,Tatai and Wad Elmagdi minor canals, respectivly. This
could be attributed to the deterioration of gates and weirs, which
led the irrigation authority to adopt constant daily rates of 10,000
m3 (Baranco and Tatai) and 40,000 m3 (Wad Elmagdi minor).
