Some other suggestions would be the two may be unrelated - occasional white smoke does not equal losing half coolant reserve tank in 2 hrs.
If you are low on oil , coolant can get very hot and leak out of a weak point on coolant pipes etc. If pipes are ok see above comments. ( if you run coloured and sented coolant you should be able to locate a leak. )
Occasional white smoke is usually humidity condensing in the exhaust , slow head gasket leak or water of combustion. With your location I would say humidity.
Check when it happens eg after rain.
.....Unless you have a slow gasket leak at low revs that becomes a faster one at higher revs.