Definition of "runnel"

Spring, is ye comen in, / Dappled larke singe, / Snow melteth, / Runnel pelteth, / Smelleth wind of newe buddinge.

1892 March, “Mother Talks—A Spring Walk”, in Cora L. Stockham, Andrea Hofer, editors, The Kindergarten Magazine […], volume IV, number VII, Chicago, Ill.: Kindergarten Publishing Company, page 471, column 2

Every little runnel in the bay was astir, and yet the land around him was as dry as flax, and no drop of rain had fallen.

1902, John Buchan, The Outgoing of the Tide

[…] great chambers in the rock where all sorts of plants were growing, under windows which had been cut to let in the sun, and glazed to adjust his warmth, and where runnels of water ran between fruit trees and seedlings, pumpkin plants and herbs.

1998, A. S. Byatt, Elementals: Stories of Fire and Ice, Chatto & Windus

Not all saltmarshes are suited to habitat modification, but where they are, runnelling provides long-term and cost-effective control with minor non-target impacts.

2009, Neil Saintilan, Australian Saltmarsh Ecology, page 176

The people who settled here weren’t farmers. They hunted. Yet they built a large amphitheater of mud, a platform carefully runneled to carry liquid—possibly blood.

2014, Paul Salopek, Blessed. Cursed. Claimed., National Geographic (December 2014)