Been fascinated by this for years. The hydraulic calendar theory has been knocking around for a while but most mainstream stuff still pushes the ritual/astronomical angle pretty hard.
What's your weird evidence though? That's the bit I want to hear. Because I've read Maria Reiche's work and then the later stuff challenging her astronomical interpretations and honestly neither side fully convinces me.
What gets me is the sheer scale of the thing. If it was purely ceremonial you'd think smaller would do the job just as well. The fact that some lines point directly toward underground aquifers - that's not nothing. David Johnson's research on that is worth a look if you haven't seen it.
I do think these things often served multiple purposes at once and we're too keen to pin it down to one clean explanation. Could absolutely have been calendrical, ritualistic AND practical water management all wrapped up together. Ancient peoples weren't less sophisticated than us, just differently sophisticated.
What specifically triggered your post - did you come across new research or something you found yourself?