Whether or not to drain your pond depends on how cold it gets in your area, the size of your pond, and how much time you're able to dedicate to its upkeep. Typically, only the smallest ponds, or those in the absolute coldest environments, need to be drained for the winter. Even if you do drain your pond, melting ice or snow, rain, and runoff will all make their way into your pond anyway, even if you drain and cover it. The best way to completely avoid ice damage to your pond is to winterize it and prepare it for the freezing temperatures. However, if you're worried that *all* the water in your pond may freeze solid, it may be best to drain it. Deeper ponds are more likely to be able to keep a layer of water underneath the ice on the surface. If your pond does freeze solid, this will kill fish and plants and damage your liner.
Instead of completely draining your pond, it may be better to partially drain it in order to access the deepest parts easier. This will allow you to clean out debris, muck and slime, and any organic matter at the bottom of your pond. This also makes it easier to see and remove temperature sensitive plants and fish.
