Ducks need water; their beaks will gunk up from shoveling mud, and their breathing depends upon open nostrils, which are on the upper beak. If you have two or three, they may live quite happily with access to a regularly changed five gallon bucket, but their complete well-being calls for a swim. We have ten ducks and a goose at the moment, so there are in the poultry yard several kiddie pools which, believe it or not, have to be changed out and washed twice a week. The water becomes quite brown and rich within minutes of the first swim, and in high summer also supports an explosion of algae. The mixture is too rich and questionable to apply directly to vegetables, but can be dumped around the roots of fruit trees, and is a boon in drought. This is why you have an orchard.