My 350+ pond is losing about 50% of water everyday since the weather became cold. If the filter is running, the pond then loses about 75% of water in the course of 24 hours? What could be causing this? I can see no visible sign of damage. It was the same story last year when the water got cold, but during the summer…nothing. Does water truly evaporate at an increased rate in cold weather? Or is there something truly wrong here, a phenomenon perhaps?