In terrain.ruleset, doc for "integrates" says "graphics are drawn accordingly", but that only seems to work right for roads/rails/Maglev. Not working for integrating with rivers. Requires custom ruleset to repro, so I cloned the 3.0 sandbox ruleset, hacked it the minimum required, re-named to "CanalDemo". Put the attached file CanalDemo.zip in ~/.freeciv/3.0 and unzip it, then should be able to start a game and choose CanalDemo ruleset, which needs its CanalDemo.tilespec to get the canal graphics. Don't need to actually build a canal with workers, can just use "Editing mode" to play with adding canals and rivers. Rivers and rivers, or canals and canals link up OK, but rivers and canals don't.
I suspect this has just never been implemented, so could maybe be seen as an enhancement request instead of a bug.
ddeanbrown 
Seen in 3.0.0-beta2 and in 2.6.4
In terrain.ruleset, doc for "integrates" says "graphics are drawn accordingly", but that only seems to work right for roads/rails/Maglev. Not working for integrating with rivers. Requires custom ruleset to repro, so I cloned the 3.0 sandbox ruleset, hacked it the minimum required, re-named to "CanalDemo". Put the attached file CanalDemo.zip in ~/.freeciv/3.0 and unzip it, then should be able to start a game and choose CanalDemo ruleset, which needs its CanalDemo.tilespec to get the canal graphics. Don't need to actually build a canal with workers, can just use "Editing mode" to play with adding canals and rivers. Rivers and rivers, or canals and canals link up OK, but rivers and canals don't.
I suspect this has just never been implemented, so could maybe be seen as an enhancement request instead of a bug.