Water deficit
"Cumulative difference between potential evapotranspiration and precipitation during a certain period in which the precipitation is the smaller of the two." (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