A long 3-wide water canal, with some rabbits flowing down it. The entire canal has only one source block, on the far left.
Lava flowing in a 3-wide lava canal. There are only 3 source blocks in this picture.
Canals filled with chocolate and honey from Create
Two ways to split a canal
On the left, the junction space is not "in a canal", so the water level falls further
Example of using canals to irrigate farmland
My other mod "Give Me Water Or Give Me Death" can change the max distance between farmland and water, allowing for wider spacing between the canals.