Indicators can be defined as qualitative or quantitative parameters used to describe parts of the water resources system under consideration often in ecological, social, or economic terms. In the context of decision making in water resources, indicators are used to assess the performance of the system under current and anticipated future conditions (human-induced and natural). 


For example, the annual generated hydropower per catchment, region or country is an indicator that shows how much hydropower is generated on annual basis. This indicator can be used by decision makers to assess the position of a country, for example, against a national or a regional target. Similarly, the number of households with clean water and proper sanitation at the continent level is an indicator that can also be compared against, for example, the Millennium Development Goals (MDGs).