Given the fact that it's a north facing slope (the cool side of the hill in your Great White North environment), I'd be curious how much water you really need on the site.
What are you growing? How wet is wet enough? Is this to enhance the growth of grass for livestock or for putting up hay/fodder for the winter?
Would swales unconnected to any other water feature (like a pond) be enough to slow, spread and sink enough water to keep the entire property hydrated? If you want to build ponds, I'm assuming you have a vision for using that pond for something—growing fish, keeping ducks, sailing little boats . . . something. But if the desire is just to hold more of that water on the land before it washes off, and to build soil and bio-mass on site, then multiplying the number of swales could be less expensive and more effective.
But if you are intent on ponds, I'd agree with the folks above: using natural materials on site seems more of the permaculture way. I don't think you need to import anything other than a couple of pigs and some food for them to eat. If you haven't seen this thread on using pigs to gley a pond (in horribly rocky soil without any clay to speak of), it's fascinating. Take some time and read through it. I'm always amazed with the creativity of some people on this site.
https://permies.com/t/38201/Progress-Gleying-Pond-Pigs
Stealing a line from the hippocratic oath, first of all, do no harm. You don't want to do anything to your land that you will then have to undo and try to repair or remove in 10 years when the full extent of the harm is revealed. Measure twice, cut once --- take your time and really think it thought (which you seem to be doing) before you start moving dirt.
Best of luck with your project.