The Royal Water Gardens use water channeled from Tissa's Reservoir to a series of smaller tanks, and from there to the gardens themselves. Settling pits, like the one seen here, trap debris and sediment from the water by the action of gravity; in addition, since the intake channel (right) is narrower than the exit channel (left), then according to Bernoulli's Principle this design would also reduce the speed of the water as it flowed out of the chamber.