Garden pond leaking

[Jim]

My garden pond has suddenly drained. Its a concrete one and I have found a hairline crack which may have been caused by movement or maybe a tree root. I am not keen on putting a liner in and wonder whether there is a special form of cement that would seal up the crack for now anyway. Any ideas please.
Jim

 

[nstreet]

see here http://www.mywatergarden.co.uk/leak-in-pond-pool.htm and here http://www.pond-doctor.co.uk/bradshaws_ponds_pumps_0036.htm