The Namal Dam and canal was opened on 2nd December 1913 by His Honors the Lieutenant-Governor Sir Michael O' Dwyer. An interesting description of the dam and canal was contained in a speech made by Colonel R. S. Maclagan, C.B., C.S.I., at the opening ceremony and is reproduced below:-The dam closes up a narrow gorge of limestone rock, thus forming a large lake above it, the water i.e of which, with the normal rainfall, will, it is calculated, stand at R. L. 1,l60, i.e 20 feet below the crest of the weir, and will contain 630 million cubic feet of water. This will suffice to supply a small canal with an average discharge of 42 cusecs for the Rabi. The crest of the dam is built at R. L. 1,180, which is 20 feet above the normal water level and at the two sides are waste weirs, which are calculated to carry off the highest probable floods. The main supply of water in the reservoir is obtained from streams on the northern slopes of the Salt Range.The dam is designed of what is known as the gravity section.
The geology of the Dhak Range can be very conveniently studied in a gorge at the eastern end of which the Namal dam has been constructed. Here there is a Tertiary series, consisting of alternations of soft grey and greenish grey sandstone, and red and brown clays, overlying Nummulitic limestone. This limestone varies greatly in character in different bands. At the site of the dam the limestone dips at 65 to the north-east. The dip, however, decreases in height: in fact, the beds are the eastern arm of an anticline, the top of the arch occurring near the western end of the gorge. Close to the limestone ridge, the Tertiary sandstone and clay has been denuded away, thus forming a longitudinal valley parallel to the ridge. Hot water and sulphureous springs emerge at numerous points in the gorge and are not confined to any one particular formation. There are a number of these just below the site of the Namal dam. Hot water and sulphurated. hydrogen gas issues from numerous cracks in the rock. In some cases hot water rushes out in considerable quantity with a large escape of gas while others issue quietly. The water is covered with a thin film of gypsum and at the bottom of the pools is a deposit of thick black mud.(Ref: Gazetter of Mianwali 1915)
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