Snow Globe from London

I love snow globe...and I love collecting them. But at times when I find the water in the globe reduce, I will be annoyed and at loss because I have no clue how to get it fix. Just the other day I found one of my favourite (the biggest) snow globe from London was going through the same fate (T.T).

I hardly shake the snow globe, I do not place them near the window and I'm always careful when handling them. Regardless how careful I am, it will still come to this stage >.< Although I have found some useful idea on the internet to restore the water...but I just don't have the guts to do so...as I'm afraid I will make it worst. *Sigh*  

I guess I have to stop myself from buying them at the moment....till I figure out if there is anyway to solve this problem?