I have a quite large, fairly shallow pond that is about 65 years old, and the
cement finally cracked after about 60 years. I drained it a few summers ago,
and cemented up the cracks.

All was fine for a year or so, when all of a sudden I started losing water
again. I haven't located the leaks, and suspect that the best thing will be to
drain it and apply either a skim coat of cement over the entire surface, or
perhaps consider a liner. This will also give me the excuse to knock a large
hole in the bottom and dig a section down a metre or so for more depth for
lilies and fish.

As an interim measure I have just been topping it up this year, but that is
always a hassle wondering if you've forgotten to turn the hose off etc. As it
happens, I just had an automatic watering system installed in the main garden,
and it gave me the idea of using a small timer that attaches to the hose bib to
turn the hose on regularly for a certain time to top up the pond every day. I
should have done that long ago.

I also gave in to a sudden urge when at the garden centre picking up the timer,
and also bought a gargoyle fountainhead for all of about $20, which I stuck on
the end of the hose I use to top up the pond. The look on my wife's face when
we were sitting by the pond and the timer turned on and the gargoyle,
previously unnoticed, started spewing was worth it. She cheered up considerably
when I told her I hadn't spent a bunch of money and wired a fountain pump in -
it was just a fancy hose end that worked every day for an hour or so.

Next year - concrete work!