Size and Depth -First dig out a sufficiently large hole to the size of the water garden required, plus about six inches in floor depth, and at least four inches in width for each wall. This space allows for solid construction. The floor of the pool should be made sloping, partly to enable the water to be run off easily, but more particularly to allow differing depths of water for the fish which are normally kept in such water gardens. Shelter should be provided for them by an overlapping edge; by a few rocks built into a cave-like structure under the water; or solely by the use of water plants.

If fish are to be introduced, the bottom of the pool should be a least fifteen inches deep at the Shallow end, to eighteen inches at the deep end. This is hardly enough depth .for plant growth, however, so if the pool is no deeper than this, pits must be made in the bottom for planting; nine inches square by nine inches deep being a useful size. These must obviously be made as the building of the pool progresses, otherwise much more complicated constructional work will be necessitated later.

If water gardens are two feet or more in depth and Lilies are desired, these should be grown in pots or tubs, and stood on the floor of the pool. This simplifies the task of renewing the soil and replanting.

Children's water gardens should be shallow for safety. If they are to be

just paddling water gardens, they could be from three to six inches at the shallow end, to nine or twelve inches at the deep end. Here the importance of the inlet, outlet and overflow is particularly apparent, as it will be necessary to keep these water gardens scrupulously clean.

A tap at the side (with a key which can be removed), will greatly facilitate this work. Care must be taken to keep such water gardens filled with water, for it evaporates quickly where there is little depth, and dry concrete may crack in the summer and cause leakages.

Fixing The Plumbing- All pipes should be laid before the pool is concreted. For the inlet a length of water pipe is run from the garden line into the pool, and a control tap is placed in a box in a handy position. The water may be run in at the side of the pool, or the pipe fitted with an extra vertical length, and a spray nosel placed at the top of it, making a simple fountain In the centre. If It Is cut to appear an inch or so over the surface Of the water, At will be quite satisfactory. Or one or more Sprays may be placed at the edge of the pool,and allowed to play on the surface of the Water. If, however, a high spray is wanted, then some device must be worked out to camouflage the pipe. For instance,- it could be set in stone or, as is often done, constructed to run through some piece of statuary. In the informal pool at the edge of the rockery, the water can be made to splash and fall down in a miniature waterfall.

The overflow is made by inserting a piece of three-quarter-inch piping one inch below the surface of the pool. This pipe takes a downward bend, and runs into the lawn or garden bed, where it discharges its water, which gradually drains away. Better still, it can be run into the nearest agricultural drain, or into the storm water pipe. It is illegal to run any garden pipe into the sewerage system.

The outlet is made by setting an ordinary kitchen sink plug, with strainer, into the bottom of the pool at the lowest corner. The plug chain is connected to the wall of the pool near the surface. so that it may be removed without any difficulty. A one-inch galvanised iron pipe is set to run the water away, and is usually connected with the overflow pipe, so that only one length is needed from this point.

Brick and Cement -There are. several methods of constructing a pool. The simplest is to dig a straight-sided, even-. floored hole to the depth required, allowing space for construction. The soil of the floor should be well rammed before further work commences so as to overcome any danger. of a subsidence later.

Build a brick well, laying the bricks, with cemented joints. Make the floor first, and build up the walls on this. The bricked area should reach to within about two inches of the surface, so that a stone slab edging can be laid on top level with the lawn. When the brick work is completed, it should be given a half-inch coating of cement and a waterproofed finishing.

Concrete Water Gardens.-A concrete pool, reinforced with rubble, is quite satisfactory. It is not essential to make the sides of this pool vertical; they may slope to the centre of the bottom, something like a shallow bowl.

Line the bottom with rubble to several inches deep, but do not ram it in, as the mixed concrete should be poured on and allowed to fill the interstices. If it is possible to reinforce with steel rods, so much the better. The rods should be long enough to go across the bottom and up both sides, and naturally they must be bent to the shape of the pool, and embedded in the rubble.

Concrete the bottom first. It will be necessary to build boxes to hold in the walls of the pool. The cement mixture should be made up of one part cement to two parts sand mixed with the smallest amount possible of water; one part should be sufficient. This Must be run over the bottom of the pool and rammed well in between the rubble to make sure that no air spaces are left. The walls, which are not vertical, will have already beep lined with stone and steel rods, and boxed. Run the concrete mixture in, and finish off the pool by well mixing together two and a half parts sand, one part cement, and the prescribed portion of water proofing, with one part water. Surface the sides and the bottom of the pool with the mixture. Waterproofing should be used according to the directions given by the maker.

The edge of the Water Garden -If the pool is of a formal type the edge is finished with one to two feet wide stone, or concrete slabs, set in a bed of concrete to form a path.
If the pool is an informal one, it can have rock pockets around it, with small spaces left for the setting of stepping stones. The rocas nearest the pool are beat concreted in posttibn, but in such a way that no part of the concrete is visible.

Maturing the Water Feature -The pool should be filled with water as soon as the surface has hardened, and Should thereafter be kept full., But it is not yet ready to support life, new concrete gives off chemicals poisonous to t or fish life. To overcome this, the 001 - la filled with water, left for a week or so, and then emptied and the walls and floor scrubbed with a stiff broom. This should be done three times before any plant life is Introduced. If the plants do not seem to suffer, it is sate to release fish in the pool as the water should be sufficiently pure.

The matured pool will develop certain algae on its walls and floor of value to fish. This growth helps to keep the correct balance between plant and fish life, and must be allowed to grow within reason. Any surplus growth, which spoils the beauty of the pool, should be removed, by scrubbing the sides.