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In this article, we study the performance of international water management at Lake Titicaca in order to assess the empirical applicability of a new concept for measuring policy performance. This performance measurement concept (PER) is a function of three variables: optimum performance (OP), actual performance (AP), and counterfactual performance (CP). In examining the joint management of Lake Titicaca by Bolivia and Peru we identify practical difficulties in applying PER and suggest extensions of the concept to assess uncertainty. We find that this measurement concept has several advantages: it takes into account counterfactual performance; the analysis can be performed in a structured, standardized, and transparent manner; and the formal framework allows for an assessment of uncertainty. Problems in applying the concept include: choice of attributes, identification of optimum performance, time-scale, and subjectivity of information. We conclude that, on balance, this approach is superior to other policy performance assessment measures developed to date.

Ecologically based criteria require an integrated modeling approach. Due to the complexity of the system, the stochastic nature of loads, and the model abstractions, many uncertainties are involved. In this study, a simple integrated model is applied, which Swiss engineers employ to assess the impact of urban stormwater discharges on riverbed stability. In the course of a case study, an uncertainty analysis is carried out focusing on parameter uncertainties. The underlying context of the uncertainties is evaluated, and a variance-based sensitivity analysis is presented estimating the local uncertainty contribution of each parameter. The results reveal that the largest contributions stem from the model components describing the natural system. An experimental design is proposed that manages to reduce the output uncertainty significantly. Finally, we discuss the benefits of following the proposed procedure.