Water balance
"Inventory of water based on the principle that during a certain time interval, the total water gain to a given catchment area or body of water must equal the total water loss plus the net change in storage in the catchment or body of water." (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