The intention is for the tank to be stored in their Hub (see https://ewbchallenge.org/challenge/dawul-wuru-aboriginal-corporation/vision-of-a-collective-hub-on-country/). Dawul Wuru are interested in having a space where they can host researchers and record traditional knowledge about different species which Elders can’t normally go and see in the field.
The size of the tank will be up to you to determine – what do you think is an appropriate size given its location and purpose? It’s also important to keep in mind the contextual information about Dawul Wuru, particularly regarding land tenure in Yirrganydji Country. How can you make the tank mobile if it needs to be relocated?
Dawul Wuru and the rangers are definitely key stakeholders in your project. There will likely be additional stakeholders, and as your design proposal progresses, these will become clearer; you can think about who are the end users of your design, who might be impacted by it, what permissions you might need etc to identify who your stakeholders could be.
Hope this helps!