This is an old fashioned wind-powered water pump that is pulling water from the pond in front of it. I remember seeing lots of these devices around when I was a child and we drove out to the country, but to a very large extent, these have been replaced by electric powered pumps.
Yes it was raining when I took this picture and I hurried back for shelter and got there a few minutes before a real cloud-burst. A tripod and a slow shutter speed show motion of the windmill.