The good thing about kelpies and heelers - they can be a handful at the start, but they are so smart and keen to train that with a little bit of work you can get a whole lot back
I currently have kelpies, they're going to be on a suburban block for about the next month and they haven't worked a sheep in 4 months. They get about half the exercise in the OP but they've been asleep all day even though they haven't been walked. They weren't always like this, so I'll put down a few things that helped:
- Clicker training. Smart dogs need their brains worked as much as their bodies. Everyday training of tricks, household chores, obedience, agility, whatever, just 5 minutes or less a few times a day. Shaping exercises like 101 things to do with a box (on google) keep that brain active too.
- Reinforcing calm. Lying relaxed on their bed will be rewarded. Frozen kongs are good for this too.
- Teach a "quiet" "inside" and "on your bed" to interrupt the barking when it starts and redirect to something else. The "quiet" cue I taught by holding a treat in front of their face until they shut up to look at it, then marked and rewarded that behaviour, then increased the time they had to be quiet before I rewarded.
- If you have any herding training near you it's a great outlet for them and heaps of fun
Punishing might stop the barking, but she's barking for a reason. Make sure you give her another option to release that energy or it might be digging or chewing next! I grew up with a heeler x kelpie so have a huge soft spot for them