From a surface of sixteen square feet, about a bucketful of water escapes every day by evaporation and transpiration of the plants. Stagnation is prevented by having a few fish and some submerged plants like Cabomba or Myriophyllum. It is therefore very easy to care for a garden up to six by twelve feet, even with only a bucket to supply water.
On the other hand, a large pond fed by a natural stream will often be in danger from floods. Unless the stream be very small in proportion to the lake it will be necessary to have means of diverting it into a culvert or sluice on occasion.
Floating parts of plants have very remarkable powers of accommodation to the depth of the water. Water-lily leaves may be entirely submerged in the evening, and by next morning their stalks will have grown just enough to spread them on the surface again. But on all considerations, it is desirable that the water level should not vary more than four inches at the most; even this amount may bring into view ugly strips of mud or masonry. An outlet of ample size is as necessary as an inlet for the regulation of the water supply.
Small ponds on level or gently sloping ground may be allowed to overflow their sodded margins. If fed by a continuous open stream, it may be most artistically led away in a similar manner, either directly, or by a waterfall, or through a bog garden.