Runnel
/ˈrʌnl/
Definition 1 of 2
Pro Tip 1/3Natural Settings
Use 'runnel' to describe natural water flow in outdoor landscapes. 
Hiking along the path, we listened to the murmur of runnels weaving through the meadow.
Pro Tip 2/3Size Matters
'Runnel' implies a very small, narrow waterway, smaller than a creek. 
Children jumped across the shallow runnels searching for pebbles and shells.
Pro Tip 3/3Visual Imagery
Use 'runnel' to evoke imagery of serenity or quiet movement in literature or descriptions. 
The runnels glittered under the moonlight, threading silver through the dark forest.