scientific advice. What are the elements of such advice and information? What principles should guide scientists in developing and rendering scientific advice? The remainder of this paper is devoted to a characterization and discussion of the elements of good scientific advice, particularly as it is applied to the management of water systems.
Principle # 1: Frequently, scientists compromise their effectiveness and credibility by failing to distinguish among scientific information, scientific interpretation and policy value judgments. There is an understandable resentment among policy makers about scientists who behave as if their scientific backgrounds make them especially qualified to make policy value judgments. Policy value judgments are inherently non-scientific and scientists are no more qualified to make them than anyone else. In addition, scientists frequently compromise their effectiveness by failing to be clear about what is scientific fact and what is an interpretation of that fact. The first fundamental principle that should govern the development of good scientific advice can be stated as follows: It is crucial to distinguish between fact and what follows logically from fact, on the one hand, and interpretation of fact and value judgment on the other. This is not to say that scientists should be restrained from rendering interpretations of scientific fact and value judgments about the formulation policy. Rather it is to emphasize that scientists must make clear when their advice contains elements of interpretation or policy value judgments.
Principle # 2: There are at least three distinct dimensions of scientific advice which can be offered either independently or in conjunction with each other. These are: 1) existing scientific knowledge; 2) interpretations of existing scientific knowledge; and 3) methods for acquiring scientific knowledge. Existing scientific knowledge is comprised of information that is known with certainty, information that is known probabilistically and information that is uncertain or unknown1. It is rare that scientific information is known with complete certainty and there are circumstances in which information is unknowable with scientific certainty. In rendering scientific advice, it is thus important to inform the decision maker of the relative degree of risk1 or uncertainty associated with specific pieces of knowledge so that risk and uncertainty can be accounted for in designing policies and management strategies. Similarly, interpretations of scientific information rest in part on what is known with certainty; what is characterized by risk and what is inherently unknowable and uncertain. Again, in making scientific interpretations, it is important that the scientists be very clear in describing the extent to which a given interpretation is based on hard knowledge and the extent to which it is based on probabilistic knowledge and/or judgments even where they are employed to reduce uncertainty.
There are other circumstances where scientific advice will not consist of scientific information at all but rather in the characterization and design of processes or methods for acquiring scientific information either on a one-time or on a continuing basis. Here again, reliability and accuracy are important characteristics of any system that generates scientific information. The task of the scientist in these situations is to provide knowledge not just about methods and processes for acquiring scientific information and their design but also to characterize ex ante the reliability of