The South American Atlantic rainforest is a one-of-a-kind ecosystem considered as a biodiversity hotspot; however, in the last decades, it was intensively reduced to 7 % of its original surface. Water resources and water quality are one of the main goods and services this system provides to people. For monitoring and management recommendations, the present study is focused on (1) determining the nutrient content (nitrate, nitrite, ammonium, and phosphate) and physiochemical parameters (temperature, pH, electrical conductivity, turbidity, dissolved oxygen, and total dissolved solids) in surface water from 24 rainforest mountain rivers in Argentina, (2) analyzing the human health risk, (3) assessing the environmental distribution of the determined pollutants, and (4) analyzing water quality indices (WQI(obj) and WQI(min)). In addition, for total coliform bacteria, a dataset was used from literature. Turbidity, total dissolved solids, and nitrite (NO2-) exceeded the guideline value recommended by national or international guidelines in several sampling stations. The spatial distribution pattern was analyzed by Principal Component Analysis and Factor Analysis (PCA/FA) showing well-defined groups of rivers. Both WQI showed good adjustment (R-2 = 0.89) and rated water quality as good or excellent in all sampling sites (WQI >71). Therefore, this study suggests the use of the WQI(min) for monitoring water quality in the region and also the water treatment of coliform, total dissolved solids, and turbidity.