A Multicriterion Decision Making (MCDM) concept is applied to provide not only possible solutions for a hydro-ecological problem but also to shed light on the discriminating capabilities of criteria. The aim is to identify a subset of a given set of criteria used to seek a satisfactory solution among several possible water resource projects being designed for the Austrian part of the Danube between Vienna and the Slovakian border. In this section of Danube is still a free flowing river and possesses a high ecological value. There are three conflicting interests relative to this particular area, namely economic, ecological and sociological interests. The so-called Multicriterion Q-Analysis (MCQA) technique is applied to generate more effective discussions between conflicting groups than there had been in the past. The most preferred alternatives from among twelve possible projects, including several different hydroelectric power stations and National Park plans is to be identified. The MCQA procedure is implemented to analyze the water resource projects with emphasis on criterion evaluation. In order to facilitate ranking alternatives, criteria with discriminating power have to be defined. For this purpose, a new concept, MCQA-III, is developed and shown to be useful tool to distinguish between important and less important criteria. MCQA techniques are based on Q-Analysis, which describes the geometrical structure of the relationship between two finite sets, here the set of projects and the set of criteria. By using MCQA-I, MCQA-II and MCQA- III, a ranking of both alternatives and criteria is obtained. MCQA-III procedure is applied to find an order among criteria which should give us more information on their worth or importance for ranking alternatives, leading to a possible reduction of the number of criteria.