In the somewhat amusing video below a guy checks to see if his water tank survived the winter.
Essentially the message I want to get across here is that every April you should be checking the status of your water tank to see if there any damage to it, any leaks, any repairs that are needed, whether it is tipping in any direction (it could happen...) and the overall status of the water tank.
In the above video they used a tarp / rain water collection system, wherein the rain hits the tarp, flows into the water tank and is then stored. In theory if they ever needed more water capacity, they should simply add more tarps / a larger tank. The water is then filtered before using.
Back in the Autumn we can also assume that you took steps to make sure your water tank survived the winter in the first place. If you did not, sucks to be you.
Along with checking the water tanks you will want to check the pipes - to make sure there is no blocks or leakages.
And lastly, check your water filtration system. You may need to clean or replace any filters.
And as they say in the video: "You never miss the water until the well is dry."
In which case you we could paraphrase that to:
"You never miss clean water until the water filter breaks."
Below are some sample off grid water systems other people have done.
The last one I really like as it is using water from a source further uphill and could potentially be used to provide electricity too.