A surface pump may be used to draw water from the pool for delivery to the top of the cascade, waterfall or the beginning of a stream. Flexible plastic liners are very useful in developing a pool and short water course. They allow one a lot more flexibility in the design of a water garden compared to preformed metal, fibreglass, or plastic liners. The flexible synthetic rubber or plastic provides a waterproof barrier between the soil and the water. These flexible liners are available in a wide range of sizes, and can be cut to fit any shape of pool.
Butyl rubber is probably the best pool-lining material.
It is stronger than either polyethylene or PVC, with a life expectancy of about 30 to 40 years. PVC liners are reasonably strong and some are guaranteed for 10 years. After several years of exposure to sunlight they may harden and crack. Polyethylene is by far the cheapest of the lining materials. It is prone to tearing and cracking after constant exposure to sunlight.