Yes, that's how I made the center clear of grass for the park version here: https://steamhost.cn/steamcommunity_com/workshop/filedetails/?id=413442330 . I like leaving some grass around the edges though, since it looks kind of like reeds.

As for the other issue, you don't usually find ponds on the side of hills, do you? That would really be more of a waterfall :P. But in seriousness, yes I have been looking for a way to make it work on rough terrain. I'll be sure to update it if I come up with anything.

I loved using this for my Florida park. I found a solution for the grass that sticks up through the water. Put "ruined ground" underneath the water squares... One side issue: it seems to require the park to be absolutely flat, otherwise the water will pool to the lower side lol. Very realistic, but I wonder if there is anything that can be done?