河川

1. Origins, structure, and basic meaning

• Structure: 河川 is read as かせん and is a noun for rivers and waterways, especially as a collective term in administrative or environmental contexts.
• Basic usage: Patrolling local waterways after rain appears in 地域の河川を見回る, while testing river water quality appears in 河川の水質を調べる.

2. Common pitfalls and similar expressions

• Management and environmental study
  • It readily appears in public-management contexts such as patrolling waterways or testing water quality.
• Difference from 川
  • Compared with the everyday word for an individual river, this is a formal collective term used for classification and management.