[Marianne]

we found a great way to stop water from freezing.
if you have power to your run hang an infra red light over the drinker .
these are used for heating chick incubators and are available from most agricultural suppliers .
a timer can be used if needed these can be bought from most supermarkets cheaply
remember to  keep  out of the rain
hope this helps
marianne

[arugula]

Nice idea Marianne! Beware though, as pointed out recently, of using electricty outdoors:

http://chat.allotment-garden.org/index.php?topic=69101.msg790007#msg790007