Pump pumps out water overnight

Question
Hello,

I have 2 ponds, one large and one small (the plastic ones from home depot), sitting next to each other and have had them for about 3 years now.  I have a pump with a bell shaped fountain running 24/7.  I take a look at my ponds every morning so this problem happened overnight.  The pump looks fine in the morning and afternoon, but for some reason pumps out water overnight.  By this, I mean the pump spits out water over the edge of the pond.  So I wake up to find my pond with only a foot of water left.  My poor fish!  This only happens in the small pond.  I am assuming that since the large pond is huge, no matter how far the water spits overnight, it still falls within the pond.  This does not happen everyday and it is the first time it has happen in 3 years.  I've tried changing the fountain to a fish spitter.  In the morning I found evidence (wetness in the area) that the spitter was not spitting far enough into the pond, so the water never makes it back into the pond.  I'm at a loss.  Does it have to do with the climate casuing more pressure in the pump or something?  Thank a bunch!

Answer
OK this is a head scratcher at best. Two things does the area get windy at night or is there an intruder who diverts the water? Fiirst off where do you live ? I am betting on a prevailing wind. Do you live in the country or the city?
 If you answer these question I may be able to find a solution.


              Keep Ponding
                Leigh