downgradient

Etymology
From.

Adjective

 * 1) A position down along a gradient from a starting position.
 * 2)  a location that receives groundwater from another location; similar to downstream.
 * Monitoring wells are installed downgradient of a contamination source to detect a contaminant plume.

Adverb

 * 1) The direction along a gradient.
 * 2)  a direction that groundwater flows toward.