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Abstract
Scarcity of water in Egypt is becoming a problem due to limited water resources, increasing population and increasing consumption of different sectors of the society. Therefore, the Egyptian government is integrating activities towards optimizing benefits for saving water resources. One of the most important efforts of the Egyptian government in this regard is the conservation of water and reducing water losses. Therefore, all canals in the newly reclaimed areas must be lined to reduce the water losses due to seepage. Seepage of water from irrigation canals is a serious problem. Not only is the water lost, but also drainage problems are often aggravated on adjacent or lower lands. Therefore, evaluation of actual seepage losses in lined canals needs to be studied.
The main objective of this study is to evaluate the seepage losses from lined canals in the West El-Nubaria region, where all canals are lined with concrete. Seepage occurs mainly from badly executed expansion joints. The effect of shut off periods on the rate of seepage losses was also investigated. To carry out this study, two lined branch canals in the West El-Nubaria region were chosen. These branches, No.11 and No.18, are fed from El-Nassr main canal.
The ponding method was used to measure seepage losses from these canals. Field measurements were carried out to investigate the rate of seepage at different reaches and at different conditions. Evaporation losses were not allowed during field works by covering canals by plastic sheets.
Different relationships between rates of seepage losses, time and wetted perimeter were developed and analyzed. It can be concluded that the rate of seepage losses decreases with the increase of time, decrease of wetted perimeter and water depths. It can be also concluded that good execution of expansion joints has a great influence to reduce the seepage losses. Moreover, the rate of seepage losses increases with the increase of shut off period.
It was found that the average percent of seepage loss per unit length (km) of the tested canals ranged from 0.06% and 1.07%
A comparison between the measured seepage losses obtained in this study and estimated seepage losses using some empirical formulae showed great difference because these formulae ignored the seepage from joints.