Complex sentence: The canal was almost finished in 1774 but the inclined planes were not in working order, one problem being their steepness and also Farlough lake, one of the canal's water sources was providing insufficient water.
Split into simpler sentences: The canal was almost finished in 1774 but the inclined planes were not in working order. One problem was their steepness and another that Farlough Lake, one of the canal's water sources, was providing insufficient water.