We have had the 'same' water in our pool in Corfu for 4 or 5 years.
At the end of October we take the pump out to stop it from corroding too much (pump house underground - BIG mistake - NEVER do it!!), then empty about 2 feet of water and chuck in half a dozen chlorine tabs and leave it.
The winter storms usually means that someone has to go and take more water out 2 or 3 times in the winter and they also put in some more chlorine tabs as necessary.
Result is that at the end of April the pool looks filthy with leaves and dirt etc on the bottom but the water is clear.
We put the pump back in, top the pool up, vacuum and backwash 2 or 3 times over the next few days and it is as good as new. First time I saw the pool after the winter I panicked, but now I know it will recover in no time at all.
Plus bear in mind everyone is talking about a water shortage this year after the mild winter so as much water than can be saved the better.