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|Above Stronachlachar, looking eastward along the length of the loch|
|Lake type||freshwater loch, reservoir|
|Basin countries||United Kingdom|
|Max. length||13 km|
|Max. width||1 km|
Loch Katrine ( listen (help·info); Scottish Gaelic: Loch Ceiteirein or Loch Ceathairne, pronounced [lˠ̪ɔx kʲʰeʰtʲəɾʲɛɲ]) is a freshwater loch in the district of Stirling, Scotland. It is roughly 8 miles long by 2/3 of a mile wide and runs the length of Strath Gartney (Gaelic: Srath Ghartain). It is a popular destination for tourists and day visitors from Glasgow and other nearby towns. The loch derives its name from the term cateran from the Gaelic ceathairne, a collective word meaning cattle thief or possibly peasantry. Historically this referred to a band of fighting men of a clan; hence the term applied to marauders or cattle-lifters, the most notorious of whom was Rob Roy MacGregor who was born at Glengyle House at the northern end of the Loch.
Loch Katrine is owned by Scottish Water and is the primary water reservoir for much of the city of Glasgow and its surrounding areas. The water level has been artificially raised by around 6 feet - the Loch can be drawn down by a maximum of 7 ft in order to provide gravitational flow to the Milngavie water treatment works via two 26 mile long aqueducts and 13 miles of tunnel. Milngavie itself is situated at almost 400 ft above sea level - sufficient to provide adequate water pressure to the majority of Glasgow without the need for pumping. The system can deliver up to 50,000,000 gallons a day. Construction was started in 1855 and the works was opened by Queen Victoria in 1859. The aqueduct project was built under the guidance of the eminent Civil Engineer John Frederick Bateman (1810–1889), an example of his engineering prowess that can still be seen working today. The second aqueduct was opened in 1901.
Water levels are supplemented via a dam and short tunnel from Loch Arklet, a reservoir located between Loch Katrine itself and Loch Lomond, beside the road to Inversnaid, this project was completed in 1914. A longer tunnel beneath Ben A'an which brings water from the Glen Finglas Reservoir was completed in 1958, with dam being completed in 1965.
Oil-fired vessels are not permitted to sail its waters due to the danger of pollution to the drinking water of Glasgow. Instead a biodiesel fueled, steam-powered boat named the SS Sir Walter Scott offers local tourist transport between Trossachs Pier and Stronachlachar during summer. Robert Roy MacGregor was born at the head of the loch.
The main access points for Loch Katrine are either via Trossachs Pier at the loch's eastern end or Stronachlachar (Gaelic Sròn a' Chlachair "the headland of the stonemason") towards the western end of the loch. Trossachs Pier essentially consists of a parking space, pier, gift shop and cafe (Katrine Cafe) which are open from the first to the last sailing of the cruise boats, (normally 6pm The Loch Katrine Experience).
On the northern shore are the Brenchoile hunting lodge and the farms Letter (Gaelic: Leitir), Edra (Gaelic: Eatarra "between them"), Strone (Gaelic: An t-Sròn "the nose"), Coilachra, Portnellan (Gaelic: Port an Eilein "port of the island") and Glengyle (Gaelic: Gleann Goill "glen of a lowlander"), on the southern are The Dhu (Gaelic: An Dubh "the black") at the western end of the loch, Stronachlachar, the Royal Cottage, Culligart and Glasahoile (Gaelic: Glas-choille "greywood").
The roads and paths do not circle the loch completely, as the southern road stops at Glasahoile.
There are several small islands in Loch Katrine such as Ellen's Isle (Gaelic: An t-Eilean Molach "the shingly isle"), the Black Isle and Factor's Island (Gaelic: Eilean a' Bhàillidh).
Other information 
Loch Katrine is the namesake of The Athole Highlanders' Farewell to Loch Katrine.
See also 
- Newton, M. Bho Chluaidh gu Calasraid Acair 1999 ISBN 0-86152-265-6
- Loch Katrine tourist brochure produced by the Scottish Tourist Board
- BBC 2, Britain's Lost Routes. Griff Rhys-Jones, Documentary about Highland Cattle Drovers
- Birmingham Museum of Art (2010). Birmingham Museum of Art : guide to the collection. [Birmingham, Ala]: Birmingham Museum of Art. p. 215. ISBN 978-1-904832-77-5.