A waterladder pump, water ladder, dragon spine, dragon wheel or rahad is a low lift pump which is composed of sprockets that moves a chain with paddles over a trough

Trough

Trough may refer to:* Trough , the lowest turning point of a business cycle* Trough or manger, a container for animal feed* Watering trough, a receptacle of drinking water for domestic and non-domestic livestock...

. Water is pumped as the paddles push the water up the trough.

Application

The water ladder, as many low lift pumps, is commonly used for irrigation purposes and for drainage of lands. It is currently still used by farmers in south-east Asia.

Advantages

The water ladder was built as an alternative to the paddle wheel

Paddle wheel

A paddle wheel is a waterwheel in which a number of scoops are set around the periphery of the wheel. It has several usages.* Very low lift water pumping, such as flooding paddy fields at no more than about height above the water source....

to get around the problem that to lift water to a greater height, a bigger wheel is needed. Despite the emergence of new pumps that operate on other principles, the water ladder remains an important tool as some of its other benefits are that they can be built and repaired easily at a very low cost. This is possible as all the components can be built from local resources, such as wood; which can be obtained and shaped into the desired form easily.

Disadvantages

As mentioned before, the pump only allows the lifting of water over a small height. This makes it unsuitable to water drainage or irrigation over larger height differences or many other pumping applications besides drainage and irrigation.