Question: Barscobe Castle used stone taken from a castle in what Scottish river?

Context paragraphs:
Anaguma castle: The Anaguma or Bear In The Hole (穴熊 "anaguma", lit.  "hole-bear") is a castle used in shogi.  (An anaguma is a Japanese badger.)  It is commonly used in professional shogi.

Carse: In Scottish geography, a Carse (the modern form of older Scots "kerse") is an area of fertile, low-lying (typically alluvial) land occupying certain Scottish river valleys, such as that of the River Forth.

Gorenji Podšumberk: Gorenji Podšumberk (] ) is a small settlement in the Municipality of Trebnje in eastern Slovenia.  It lies at the foot of the hill on which Šumberk Castle used to stand (the name "Podšumberk" means 'below Šumberk' in Slovene).  The area is part of the historical Lower Carniola region.  The municipality is now included in the Southeast Slovenia Statistical Region.

Dauphin County Veteran's Memorial Obelisk: Inspired by the classic Roman/Egyptian obelisk form, Dauphin County Veteran's Memorial Obelisk was originally erected in the middle of a park located at the North Second and State Streets intersection of downtown Harrisburg, Pennsylvania from 1866 to 1876 as a tribute to Dauphin County’s Civil War soldiers.  It stands 110 feet (33.5 meters) high, weighs over 600 tons, and was cut from stone taken from the banks of the nearby Susquehanna River.  A stone plaque is inscribed: "To the soldiers of Dauphin County who gave their lives for the life of the Union in the suppression of the rebellion 1861-1865.  Erected by their fellow citizens."

Mino castle: The Mino castle (美濃囲い "minō gakoi" or 本美濃囲い "hon minō gakoi") is a castle used in shogi.

Barscobe Castle: Barscobe Castle is a 17th-century tower house in Balmaclellan, Kirkcudbrightshire, Scotland.  It is a typical house of a country laird, and according to a panel above the entrance, was built in 1648.  The L-plan tower was constructed using stone taken from Threave Castle.  The main block is three storeys high with the stair wing one storey higher.  The gables have a modification of crowsteps found only in Galloway.  It is a fine example of a mid-17th-century house which was unoccupied for many years until 1971 when it was restored.  It has a modern byre (barn) attached, which has been converted into a garage.  Barscobe Castle is a category A listed building.

Purbeck stone: Purbeck stone refers to building stone taken from a series of limestone beds found in the Upper Jurassic to Lower Cretaceous Purbeck Group, found on the Isle of Purbeck, Dorset in southern England.  The best known variety of this stone is Purbeck Marble.  The stone has been quarried since at least Roman times up to the present day.

Threave Castle: Threave Castle is situated on an island in the River Dee, 2.5 km west of Castle Douglas in Dumfries and Galloway, south-west Scotland.

Koz Castle: Koz Castle (Turkish: "Koz Kalesi"), or Kürşat Castle is a castle in the Altınözü district of the Hatay Province of Turkey, built on a small hill where the Kuseyr Creek starts.  It was built by the Principality of Antioch out of ashlar.  The castle used to have a gate to the north, but this gate no longer exists and the eastern side of the castle has been leveled, with some original barns left.  Some bastions of the castle stand to this day.

Rivers and Fisheries Trusts of Scotland: The Rivers and Fisheries Trusts of Scotland (RAFTS) (also known as the Association of Scottish River & Fishery Management Trusts) is a waterway society, an unincorporated association, a Scottish charity, and an umbrella organisation for river trusts in Scotland, based in Edinburgh.

Supporting paragraphs: Barscobe Castle Threave Castle
Answer: Dee