looking at the end of the pipe sticking into the pond, I wish I had better news for you, but that will have to be replaced, and waiting much longer to do it could be counter productive, I've replaced a few that were in that condition.
When you say you have water trickling out of the end, is it coming out of the pipe or around the pipe?
The reason your pond is lower then normal, which is really obvious in the picture, is because you way more then likely have a hole rusted into the pipe below the current water level, but still inside the pond, that is allowing water to escape 24/7.
It is, however, much cheaper to replace it now when your water is a bit low, then it will be if you have a huge rain event and have a much bigger failure, like washing out a sinkhole, or a good portion of your dam, than you will have to import clay to replace the missing dirt in your dam.
Either way, Good Luck! hopefully it wont be too expensive to replace.
