Water can add to the attractions of a garden in several quite different ways. Still water acts as a mirror and provides the gardener with a texture sharply contrasted with that of soil, grass or plants. Moving water is exciting to the eye and pleasant to the ear. And in addition to all this, water is a medium in which a new range of plants can be grown: water plants, or full aquatics. In the deep water and bog plants, or sub-aquatics, in the very shallow water or the wet ground around the pool or stream.
Water can be used as a purely formal feature in pools of circular, oval, rectangular or other geometric formation with or without ornamental fountains, or it can be used informally as streams, waterfalls, cascades and pools of irregular shape. The formal pattern is appropriate when water is used near the house or in conjunction with rose gardens, terraces,, patterned beds and other places in which design is important. By contrast water can be used more effectively in informal ways in rock gardens, wild gardens and woodlands where the intention is to achieve a natural appearance.
Scum and blanket weed are less troublesome in shade than in full sun but, nevertheless, it is usually best to site a pool in a fairly sunny and certainly a very light place since good light adds so much to the sparkle of the water andmay refuse to flower if they get no sunshine.
Methods of Retaining Water
However water is used, it must be effectively contained. Leaky pools and streams are a constant source of annoyance and are usually very difficult to repair effectively.
There are four main ways in which water can be retained in pools and streams. One. The traditional method, is to cover bottom and sides with wet, beaten clay, a process known as ‘puddling*. In gardens it is seldom practised today partly because of the difficulty of acquiring suitable clay in adequate quantity, partly because the puddling itself is a rural art not easily imparted to those who are unfamiliar with it.
For reasons just stated, concrete, a modern material the ingredients for which are readily available and which can be prepared by rule-of-thumb methods. Took the place of clay, but it is itself now being challenged by. Two even newer techniques: the use of plastic sheets and of resin-bonded fibre-glass.
Concrete can be prepared at home with all-in ballast (a mixture of sand and gravel). cement and water, or in many districts can be purchased ready mixed and delivered to the site (a very convenient labour-saving method). Ballast is sold by the cubic yard, often referred to simply as the yard, or by the cubic metre, and cement is sold by the hundredweight or ton or in 50kg bags or metric tonnes. A suitable mix for pools is to allow 5cwt of cement to each yard of ballast (or 250 kg cement to each cubic metre of ballast).
As a rule a layer of concrete at least 4 in (10cm) thick is required for the bottom of a pool and at least 3 in (8 cm) thick for the sides and it will be wise to increase these thicknesses to 6in (15cm) and 4m (10cm) for large pools and further strengthen them by embedding special reinforcing wire mesh in the concrete. This can be purchased from any dealer in building materials as can the ballast and cement.
Whether one mixes concrete oneself or purchases it ready mixed, the site of the pool must be ready excavated to receive it. Formaloften have vertical sides and informal pools usually have sloping sides but there is no rule about this. It is largely a matter of convenience and personal taste. Though it should be observed that very shallow pools with a large surface area are more likely to suffer weed problems, particularly from green scum and blanket weed. Than those that are deeper. This is because bright light and warmth encourage these growths of algae and the shallow pool heats up more rapidly on sunny days than the deeper pool.
Sometimes shelves are made around the sides of the pools to take plants that like shallow water. Few plants need, or indeed like, more than 2 ft (60cm) depth of water and I ft to 11 ft (30 to 45 cm) is sufficient for most water lilies. A great many marginal plants like to have theirjusi covered with water but an inch or so is quite sufficient.
If a pool has shallowly sloping sides. Well-made concrete can be spread on them without slipping, but for steep slopes or vertical sides, shuttering will be needed. This means pieces of plank temporarily fixed to hold the concrete in place while it is drying.
If reinforcing wire is to be used it should be laid in the bottom and around the sides of the pool before the concrete is put in. Then the wet concrete will completely surround the wire which will become embedded in it and give it greatly increased strength.
Cement contains chemicals which are dissolved out by water and can be harmful to plants and fish. For this reason it is wise to fill a new concrete pool with water, leave it for a week or so and then empty and refill it before planting. An alternative is to paint the surface of the dry concrete with bituminous paint to keep water out of direct contact with it. This helps to ensure that the pool will be waterproof. Though this can also be done by adding special waterproofing powders or liquids to the concrete when it is prepared. Ready-mixed concrete can be purchased with a waterproofing compound incorporated.
Clearly, the making of a concrete pool involves a great deal of labour. Much of this can be avoided by using plastic sheets or fibre-glass in place of concrete.
Special sheets of P.V.C., sometimes strengthened with nylon, or liners of butyl rubber, can be purchased for pools and they are pre-welded by the supplier so that one sheet covers the whole interior of the pool without the need for joints. The plastic or rubber has some elasticity and the weight of the water on top of it makes it conform closely to the contours of the soil beneath. Care should be taken to gel the bottom and sides of the excavation as smooth as possible and lo remove any large or sharp stones that might puncture the plastic. Sand can be spread over the bottom and sides to give a smooth, slightly resilient surface for the sheet to lie on.
When the sheet arrives it should be placed across one end of the pool and carefully unrolled or unfolded across it. It must be large enough to cover bottom and sides. With at least 9 in (23cm) overlap all round. Water is then run in and the plastic sheet will settle itself snugly in place. Any raw edges can be concealed with stones, soil. Turves or creeping plants.
Resin-bonded fibre-glass is a much stiffer material and is only used to make pre-fabricated pools. This means that the purchaser is restricted to the sizes and shapes available and, having selected one, must dig a hole to accommodate it. The fibre-glass pool need not rest firmly on the soil at every point but the nearer one can get to this the better: in other words the hole must be shaped to fit the pool which, fortunately, is very light to handle and can be tried infrom time to time as the hole is being prepared.
Plastic sheeting, butyl rubber and fibre-glass contain nothing that is harmful to plants or fish so that stocking can commence immediately the pool is completed.
Making Streams and Cascades
Streams and cascades can be made in the same way with concrete, plastic sheeting or preformed fibre-glass components. The water can be recirculated from the pool either with small submersible pumps, the simplest way, or with pumps situated outside the pool and drawing water from it through a pipe. Either type of pump can also be used to operate a fountain. It is much better to recirculate water than to draw direct from a mains supply which may be too cold and will, in any case, upset the chemical balance in the pool.