Specifications of the lockstation

One lock with a lift of 2.2 m (7.2 feet).

The Construction of the lockstation

The contractors for this site were Ferguson and Wylie.

This site's original name was First Rapids, because it is the first set of rapids encountered in a descent toward Ottawa on the Rideau system."First Rapids" was used interchangeably with "Poonamalie" until the late 1850s, after which the latter name dominated. The name comes from Poovirundavalli, a town near Chennai (Madras) in India, which became Poonthamalli, that name anglized to Poonamallee. It was a garrison town for the British Army and tradition has it that the cedars at Poonamalie reminded one of the British military men of similar scenery at Poonthamalli, India.

Structures of the lockstation:

Lockmaster’s House: The defensible lockmaster's house at Poonamalie was built in about 1842. A frame second storey was added in 1893.

Engineering Structures: The1.8 kilometre artificial channel and lock chamber bypassed the original rapids. A natural depression was used to start the channel. The lock required no major repair during the 19th century.

Dam: The dam, however, has undergone extensive repairs since the mid-1800s. This structure is of great importance because it restrains the waters of the Big Rideau and Lower Rideau Lakes, and it controls the water supply from Poonamalie to the Ottawa Locks. The dam's location at the lower end of the Rideau Lakes makes it extremely vulnerable to the heavy spring runoffs common throughout the canal. In the spring of 1869 part of the embankment at the top of the cut was washed away. Local residents helped to repair the break and navigation was soon restored. Low water levels posed a problem in 1904 when a large sheet of ice broke part of the main timber dam. When the ice broke up in the spring, instead of flowing over the dam, it struck against the back of the dam and destroyed 3/4 of the structure. The break in the dam caused damage to roads and bridges in Smiths Falls and even as far downstream as Merrickville. A new dam of concrete replaced the old timber structure. That dam and weir was rebuilt in 1971 and an electric hydraulic gate installed to control the water flow.