The paper reports on the methodology and findings of a recent project on behalf of the Austrian Federal Ministry of Agriculture, Forestry, Environment and Water Management. The Ministry is seeking procedures for combining ecological and economic criteria to assess which technical urban water alternatives shall receive funding. To this end the current decision making process (DMP) for implementing urban water alternatives in Austria has been analyzed and compared with the situation elsewhere, e.g. in Sweden. The DMP entails specific requirements on assessment, whence the most common decision aid methodologies, ranging from LCA-based to multi-criteria methods, have been described and evaluated from an environmental, economic, legal and practical point of view, turning out recommendations to the Ministry. Their main points are: First the DMP should be kept as simple as possible in order to make it transparent. Second the aggregation of different criteria groups should and can be avoided. Therefore the stakeholders should not be allowed to make trade-offs. Finally clear objectives need to be stated.