There are certain situations which leaves the owner in (somewhat) control of what the newt does. If given a small swallow water area and a substantial land area the newt will most likely use both unless they are extreme (100% aquatic or terrestrial). If your newt does fine in the water than by all means increase the water, if it seems to avoid the water or does not seems comfortable then drop it. Given great choices of both will ultimately leading to the newt showing you what it prefers but depending on the species will also enjoy both without ill effects. Seeing that alpestris can be kept in both a semi-aquatic or completely means it is up to you. IMO 1/2" of water in any tank is not suitable for an adult aquatic newt which might lead to much more time on. I know my T. dobrogicus female would use the land almost exclusively if given a nice land area but stayed aquatic and would eat better if moved to a deeper aquatic setup with just a cork island. If it isnt the water volume it could be other factors like temperature, food, etc.
Have you tried different arrangements? And even if your newt does prefer mostly water it still is acceptable to make a land portion if you want it and the newt uses it. Please dont think I am being belittling or anything of the sort, I have many times asked this about different species and found out that as long as you meet the requirements the rest is up to you really. I say increase the water height/volume and obverse what happens, most aquatic newts should take well to a minimum of 4" in depth.
Hope this helps,
Mitch
