expanse of water, lake, pond
潢 centers on a broad, still body of water: an expanse of water, a lake, or a pond. The meanings all point to a large, open water surface.
潢 combines 氵 (water) with 黄, which likely contributes the sound and may suggest a broad or expansive quality, fitting the idea of a wide water surface.
The water radical 氵 beside 黄 (yellow) suggests a vast, still lake reflecting a golden sunset, making the whole scene an expanse of water.
For コウ, imagine a calm lake so wide it seems to go on forever, like a long, drawn-out 'kooooou' sound echoing across the water: コウ.