溝
コウ, みぞ, どぶ

gutter, ditch, sewer, drain, 10**32

JLPT1 G7 S13 F1736

As per 冓# (symmetry) + 水 water → symmetrical constructions that conduct water → *ditch*; *gutter*; *sewer* → *groove*.

[Full Kanji Etymology List]