Table 4.

Confusion matrix of modelled and observed BOD concentrations (all European monitored dataset) divided in classes of water quality based on European and global guidelines.

Predicted BOD class	Observed BOD class (mg O2/L)						User's accuracy
	High	Good	Moderate	Poor	Bad	Total
	< 2.5	2.5–5	5–10	10–15	> 15		%
High	2027	432	98	11	13	2581	78.5
Good	257	186	79	12	12	546	34.1
Moderate	32	31	37	18	8	126	29.4
Poor	3	8	5	3	3	22	13.6
Bad	0	3	5	2	2	12	16.7
Total	2319	660	224	55	38	3287
Producer accuracy %	87.4	28.1	16.5	5.4	5.3		68.6