Group decision-making (i.e., multi-expert) is an important subject in planning water resources. The inherent complexity and uncertainty of real world urge many experts to be involved in decision-making processes. This paper presents an application of the linguistic-label aggregation method in a real-life case study. The case was taken from a foresight exercise in Colombia (South America) concerning environmental and water resources planning in a river basin. The group decision-making problem is solved using a four-step approach based on (i) the evaluation of experts’ opinions, (ii) the aggregation of opinions for each alternative, (iii) fuzzy ranking, and (iv) final assessment. Two main issues that are new in our work is that we consider temporal linguistic labels and a fuzzy ranking procedure that is able to include the mean, the standard deviation, the fuzzy membership function and the frequency of experts’ opinions for each alternative. The approach is developed and implemented on a computational tool. Results show an efficient decision-making process, that is, the tool demonstrated to deal with shortest time frames and to increase the efficiency of the planning resources, mainly because allows the decision manager to focus on the establishment of criteria. The latter also leads to objectivity and eases the identification and discussion of elements of consensus in decisions that otherwise may be embedded in individuals’ interests.