Of or pertaining to hydrology.

having to do with the flow of water. Immune system: The complex system of organs, tissues, cells, and molecules that fights against potentially harmful organisms (like viruses) or substances (like pollen).

Pertaining to water flow.

Relating to the properties, distribution and circulation of water.

The scientific study of the properties, distribution, and effects of water on the earth's surface, in the soil and underlying rocks, and in the atmosphere.