Great Tamil Kings promoted the constructions of a network of wells, ponds, lakes and rivers. In fact, the famous king Mathurantaka Chozha constructed largest artificial lake. But very few folk know of the automatic de-sluicing system. Besides, the kings had such a system installed in most of the lakes in olden times. Let us see how these de-sluice systems applied the Venturi principle
Engineer craftsmen placed large a stone box at the bottom of a lake. And, irrigation canals lead out lake water through the stone box. Besides the craftsmen created two kind of holes in the stone box. They made larger hole for the one at the top of the stone box. Subsequently, they covered this hole by a stone sphere. Two or three smaller holes were made at the bottom surface of the stone box to carry the sluice from the bottom of the lake into the stone box.
De-Sluicing with the Venturi Principle
A worker periodically removed the stone ball covering the top surface to allow lake water to gush into the stone box. The gushing water lowered the pressure within the stone through the principle of Venturi. In turn, the lower pressure pushed the sluice from the higher pressure at the bottom of the lake. The sluice could thus enter through the smaller holes at the bottom of the stone box. Craftsmen who created the stone box aimed to achieve a 4:1 ratio of fresh water to muddy water through the stone box. Metal/bamboo/stone pipes carried this rich mix of soil and water from the stone box to the fields from the lake.
Most of the older lakes have disappeared today. Shrubs surround strange looking stone contraptions which were once cherished for their practical use.
குமிழித் தூம்பு மதகு – the tamil name for the mechanism to described above
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