The identification, assessment and management of non-point source water pollution problems can be improved through better water quality monitoring program designs. The result is often more useful and reliable information for use by decision-makers. In this study of the Svart River Basin in south-central Sweden, the results of a modified monitoring program, designed to address non-point source inputs, were compared with the results of the ongoing program. Cost, validity (addressing intended objectives) and reliability (estimated level of uncertainty) were the criteria used to evaluate and compare the design and results obtained from the two programs. The study showed that choices of variables measured, station location and sampling frequency have a direct influence on the type and value of information obtained, especially when considering non-point sources. For a similar cost, the modified program produced more valid and reliable information for decision-making than the ongoing program.