At any rate, you should try to
minimize run off going into your pond to avoid sudden water chemistry changes
(and you wouldn't want your prize fish to end up in swimming in a puddle at
Haight-Ashbury when the pond overflows). Considering that you live in SF, you
shouldn't have that much run off anyway, unless you are watering your garden
very often.-

I can minimize runoff, but what about rain? Sure it is dry around
here for most of the year, but our winter in SF is just a rainy
season. It can downpour like a fiend. Should I prepare the pond
somehow to get rid of excess water? I can easily imagine the pond
overflowing.

Thanks for your answers...