mixing zone

https://doi.org/10.1351/goldbook.14860
Area where an effluent discharge undergoes initial dilution and is extended to cover the secondary mixing in the ambient water body.
Note: A mixing zone is an allocated impact zone where water quality criteria can be exceeded as long as acutely toxic conditions are prevented.
Source:
PAC, 2009, 81, 829. (Glossary of terms used in ecotoxicology (IUPAC Recommendations 2009)) on page 916 [Terms] [Paper]