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Land-use/land-cover (LULC) pattern influences water quality, however, this relation may be different for various spatial scales. We evaluated the LULC effects on water quality of tropical low-order streams, comparing watershed and riparian zone models. Water quality parameters were analyzed separately and together using linear mixed and multivariate models. The results indicate that the forest cover plays a significant role in keeping water clean, while agriculture and urban areas lead to water quality degradation. Pasture land had mixed effects, but in general was not correlated with poor water quality. Dissolved oxygen, phosphorus, sediment, and fecal coliforms were influenced by LULC pattern at the watershed scale, while nitrogen and organic matter were more affected by the riparian zone composition. The water quality also varies with seasonal changes in streamflow and temperature. The overall water quality variation is explained better by the LULC composition within the watershed than in the riparian zone. [ABSTRACT FROM AUTHOR]