Hi Robin,
You can use the 2016 Census data to determine how many households/dwellings are in Cape York. However, I suggest you do not aim to provide every house in Cape York with a disaster resilient river pump system because they won’t all need one.
Instead, you should aim to design one system for one homestead or small remote community to share, as a pilot to test how effective your system is before scaling up. Or if you like, a few systems locally to test them first. Also keep in mind that only communities who are positioned nearby to a river might require this system.
Hope that helps,
Best of luck,
Grace