Source: The Great Interpretation of Dreams (Ibn Sirin)
A canal in a dream indicates a man through whom sustenance flows. The flow of water in it indicates the continuity of sustenance.
Source: Perfuming Humanity in the Expression of Dreams (Al-Nabulsi)
A canal indicates a servant or a messenger. Whoever sees himself digging it will gain sustenance.
Source: Signs in the Science of Expressions (Ibn Shaheen)
A canal is interpreted as goodness. Whoever sees water flowing in it will attain goodness.