ABSTRACT: This paper suggests basic methodology for expression of relationship between calculated exploitable groundwater supplies mainly in C category and groundwater qualitative parameters. The proposal includes different technique for the evaluation of single sample collection as well as monitoring of groundwater quality whereas single sample collections are of lower reliability than results of monitoring. Final evaluation is visualized through simple cartographic representation of determined categories in point and surface forms and clearly divides parts of hydrogeological structure according to qualitative criterion for groundwater treatment.