Tips to Get Water
The easiest way is dig out ice which turns into water after digging.
Also you can build water cleaning station.
All regions have at least 20% ice. Not sure what exactly that 20% means, certainly not the percentage of total slots because some regions have 66+% in one of the resources which makes the total above 100%. But it means that all regions with 20% ice are roughly similar, so you just need to find it.
If you go into planet view you can see % of resources in each region and they never get below 20%. There are also extra modes which allow you to see regions rich with ice or other resources when you choose where to land or where to expand later.
Here is an example of ice layer: