river in Shandong province
菏 is a rare kanji used primarily as a proper noun for a river in Shandong province. Its standalone meaning is tied to that specific geographic name.
菏 combines the grass radical 艹 with 河 (river), likely as a phono-semantic compound where 河 provides the sound and the river meaning, while 艹 may indicate a plant or place name. The exact historical development is uncertain.
Grass 艹 growing along the river 河 marks the He River in Shandong. Picture reeds and plants lining the banks of this specific river.
For カ, imagine a car driving along the grassy riverbank of the He River: car -> カ, and the river is lined with plants.