To manage risk,  the uncertainities must be defined and addressed. These are listed below and are all relevant to the hydrology of river basins.

Aleatory Uncertainty: Unavoidable unpredictability about the future, also known as chance, randomness or luck. Uncertainty regarding things that nobody knows.

Epistemic Uncertainty: Uncertainty due to your lack of knowledge, things that are known but not by everybody.

Ontological Uncertainty: When we are uncertain about the whole conceptualization of a problem; what the possibilities are, what the important influential factors are, what the terms mean. Essentially what are we actually dealing with?

Direct Uncertainty: an expression of numerical or verbal uncertainty about an object

Indirect Uncertainty: A qualitative statement about the strengths and weaknesses of the evidence underlying a claim about a fact, including gaps in potentially influential information.

• A - Atmospheric Sciences
• GC - Global Environmental Change
• PP - Paleoceanography and Paleoclimatology