Surplus water refers to an excess amount of water that goes beyond the capacity a particular area or system can hold. In various contexts, the term is interchangeable with other synonymous expressions like excess water, glut, overflow, inundation, abundance of water, inundation, excess fluid, inundation or deluge of water, and spare water. In agricultural fields, the term "runoff" may also be used to describe surplus water, while in environmental settings, it may refer to wastewater, effluent, or discharge. Synonyms for surplus water are often used in different contexts for various reasons, including irrigation, drainage, safety, and conservation, amongst others.