At the beginning of the 18th century, the flow of the Crinchon (river of about twenty kilometers which flows between Bailleulmont and Saint-Nicolas before flowing into the Scarpe) is weak, irregular and its waters are of poor quality. The city of Arras needs healthy and abundant water for the inhabitants and for the drinking troughs of the cavalry barracks.
In 1723, at his request, the springs that gush out in Brétencourt, a hamlet of Rivière, were collected in a reservoir, it is a vast rectangular basin surrounded by brick walls now called "Carré des sources". Its dimensions: 33 m long, 11 m wide and 8 m deep.
The works were carried out by the Military Engineering on the orders of the king, who financed them, as recalled by a sandstone sealed in a wall: "In the year 1723, under the reign of Louis XV, the sources of the Crinchon were sought and enclosed in this basin at the expense of the king"
Le Carré des sources delivers 64 liters per second of water that is extremely fresh and remarkably clear. The stream thus formed crosses the park of the castle and joins the initial bed of the Crinchon, after a course of 500 m. The flow being capricious, the system was completed by the digging of a few artesian wells, from the end of the 18th century.