The Tridaine spring was born in the XIX century when miners dewatered a Pb-Zn exploitation located in karstified Frasnian limestones. Its water was soon used for water supply. In the middle of XX century, both a quarry and a brewery installed their activities in the same region, one targeting stone, the other water. Both activities were gently coexisting until the end of 2006 when an extraction below the water table was intended by the quarry and solutions must be searched for replacing gravitational water supply, while preserving water quality. The concerned aquifer is included in a Geopark and it is under regulation due to the Water Framework Directive. Safeguard zones have also been fixed for spring protection. Several detailed hydrogeological studies were achieved since then, aiming at conceptualizing the functioning of this “already no more natural” karst system, but nevertheless the efforts to reduce uncertainties could never guarantee the environmental/economic competition outcome until the present days. In this paper, we consider the value of data acquisition and objectivity for helping in the decision making and we underline the ubiquitous difficulty of prediction of impacts on the long term in karst systems.