Stratification

"The existence or formation of distinct layers in a body of water identified by differences in thermal or salinity characteristics, or by oxygen or nutrient content." (United Nations Publications, 2013) 

Sources

United Nations Publications. "Glossary of Shared Water Resources (English-Arabic): Technical, Socioeconomic and Legal Terminology." (2013). DOI:https://dx.doi.org/10.18356/70b462ce-en