It’s great to see you thinking about the practicalities of your design in relation to the context of Yirrganydji Country!
The nursery is not something that exists at the moment, rather it is an aspiration for Dawul Wuru. As such, it will be up to you to make recommendations on the size of the nursery and its water needs. If you haven’t already read it, this question in the discussion forum addresses some of your concerns about water needs for the nursery. I’d also recommend taking a look at the page Vision of a Collective Hub on Country regarding Dawul Wuru’s aspirations for the Hub (which include the nursery), as well as the interactives which show three potential sites for the Hub, so you can get an idea of the size the nursery could be.
I hope this helps, please let me know if you have any other questions!