This interdisciplinary research programme, aimed at determining the conditions required to control water quality in groundwater areas, was prompted by a question put forward by a mineral water production company. The underlying hypothesis of the programme is that water quality is related to how agricultural systems function, i.e. interactions between all participants and their activities in the area. Two analytical models were favoured: a crop field and a spring catchment basin. A nitrate transfer model was designed and revealed that the mean winter nitrate concentrations recorded at the spring were dependent on the sum of prior mean nitrate transfers under each crop field, multiplied by the surface area of the field within the spring catchment basin. An analysis of solutions of soils obtained from under plant roots, revealed higher nitrate concentrations under maize and rapeseed (1989-1992 means: 126 and 120mg/l), and lower levels under alfalfa, hayfields, pastures and forests (23, 19, 31 and 2 mg/l, respectively). The results indicate that spatiotemporal aspects of how technical systems function on farms in the catchment area, as well as the hydraulics of the spring catchment basin, are essential factors to be considered for controlling effluents from farming systems. Nevertheless, separate decisions made with respect to farms within the wathershed should be compatible with the overall objectives for the area. It could be interesting to consider this whole area as a water territory for the purposes of collaborative water quality control.