What is a water surplus?

A water surplus occurs when the supply of water exceeds the demand for it in a particular area. This situation is significant for understanding resource management and environmental planning. In regions with a water surplus, there is typically enough rainfall and available water sources to meet the needs of the population, agriculture, and industry without leading to scarcity or depletion of resources.

In contrast, the other options do not accurately define a water surplus. The equal demand and supply would indicate a balanced situation, rather than a surplus. Poor quality water availability pertains more to issues of water management and safety rather than the quantity of water. A method of conserving water refers to practices aimed at reducing water wastage, which does not relate to the concept of surplus as defined. Hence, the definition provided by the correct choice clearly aligns with the basic principles of hydrology and resource management.