Table 2. Classification scheme of the revised ESB and the recommendation of area control according to the environmental status and the water quality standard (Kong et al., 2018)

Class	Environmental status	ESB		Ecological description and area control recommendation
		TESB	AESB	Species richness	Water quality*	Area control
A	Very good	≥95	≥3.7	Very high	Ia	Priority protection
B	Good	≥70	≥3.1	High	Ib	Protection
C	Moderate	≥30	≥2.6	Moderate	Ⅱ	Monitoring
D	Bad	≥13	≥2.1	Low	Ⅲ	Restoration
E	Very bad	<13	<2.1	Very low	Ⅳ-Ⅵ	Priority restoration

90 percentile level.