1. Introduction to Surface Water Testing

Surface water refers to the general term for various liquid and solid forms of water existing on the Earth's crust and in the atmosphere, including rivers, lakes, glaciers, marshes, channels, reservoirs, and other water bodies. It is formed through the accumulation of natural precipitation and snowfall over time and is naturally lost to the ocean through runoff, evaporation, or seepage into the ground.

Surface water testing involves sampling, testing, recording, or signaling the condition of surface water with functional use.

2. Classification of Surface Water Bodies

Based on environmental functions and protection objectives, surface water bodies are classified into five categories in descending order of function:

Class I: Primarily applicable to source water and national nature reserves;

Class II: Primarily applicable to first-level protection zones of centralized drinking water surface sources, rare aquatic habitats, spawning grounds for fish and shrimp, feeding grounds for fry and juvenile fish, etc.;

Class III: Primarily applicable to second-level protection zones of centralized drinking water surface sources, wintering grounds for fish and shrimp, migration channels, aquaculture areas, fishery waters, and swimming zones;

Class IV: Primarily applicable to general industrial water use areas and recreational water use areas without direct human contact;

Class V: Primarily applicable to agricultural water use areas and general landscape requirement waters.

Corresponding to the above five categories of surface water functions, the basic standard items for surface water environmental quality standards are divided into five classes, with different functional categories implementing their respective standard values. Higher functional categories have stricter standard values than lower ones. If a water body serves multiple functions, the standard value corresponding to the highest functional category shall be applied. Achieving the water body’s function and meeting the standard for its functional category are synonymous.

3. Relevant Standards

"Environmental Quality Standards for Surface Water" GB 3838-2002

"Technical Specifications for Monitoring Surface Water and Wastewater" HJ/T 91-2022