Water's Turn

Water’s Turn is a local festival for the village of Dunkelbild in Middenland. Held on the first week of Plough-Tide, the village sits on the edge of a large, boggy lake that provides the populace with their fresh water. A few days after the Spring Equinox (Start Growth), the lake “turns”—the cooler water at the bottom swaps with the warmer water on top. This churns up a tremendous amount of algae and scum from the bottom, giving the top of the lake a sickly green colour and horrible smell. To celebrate the coming of spring, the townsfolk bathe in the lake and fill large barrels full of the scum-filled waters. This water is scattered over the newly planted crops and tossed onto barns and houses by the local Priest of Taal. The lake is said to have curative powers and the sick, lame, and elderly travel from miles around to have the priest anoint them with this blessed water. Those travelling into town can tell that the festival is underway by the pungent odour in the air, which can be smelled from miles away.

Source

 * Warhammer Fantasy RPG 2nd ED -- Tome of Salvation pg. 146