Knockewart Loch or Loch Jargon was situated in a hollow lying area beneath Knockewart Hill in the Parish of Ardrossan. The old loch has been largely drained and become overgrown since the 19th century. The loch is recorded as Loch Jargon on the earlier maps, being then named after the prominent fort situated nearby. 

Once Knockewart Farm was established the maps use this name for it. The Ordnance Survey Map of 1897 is the first to show the loch as having been drained, through a deepening of the outflow. The reasons for the loch's drainage may be linked to the presence of the Busbie Muir Reservoir that was constructed in the glen beneath the loch, opening in 1903.

The loch's outfall waters still drain into the reservoir before continuing as the Rowanside Burn, joining the Stanley Burn, flowing over the aqueduct at the Parkhouse Cutting and finally running into the sea at Ardrossan South Beach. The reservoir is now redundant and is only used by the Ardrossan Eglinton Angling Club.

The word 'Jargoun' in Scots and refers to the twittering or chattering of birds. Knock is from the Gaelic, An Cnoc, meaning a small hill, and as such often fortified. A cairn and possible vitrified fort are located at North Hill in the Knockewart Hills and an enclosure is located near rising ground that has the appearance of having once been cleared of stone and cultivated. No field plots or clearance heaps are now identifiable. As stated earlier, a well preserved fort is present at Knock Jargon with the remains of two ramparts and ditches constructed upon the slopes, best preserved on the south-side where each is broken by an entrance.   Knockjargon is built upon a Neolithic hilltop burial cairn. The Victorian archaeologist John Smith records the name as 'Knock-Georgan'.

A map of 1654, dating from Timothy Pont's survey of circa 1604, clearly shows the loch. A dwelling named 'Jargan' is recorded and Herman Moll's map of 1745 marks, but does not name the loch. Roy's map of 1747 shows and names 'Loch Jargen', situated without an inflow burn. The 1854-9 Ordnance Survey map shows the loch as open water with small areas of woodland above and below^. In 2011 the drainage here remains inadequate and the area is dominated by marsh plants.

At one time reservoirs were also present at Whitlees, Parkhouse and Millglen. An aircraft is said to have ditched into the Busbie Muir Reservoir during WWII.