The Amazon Basin has a large amount of water that must be conserved to meet the needs of this and future generations. This study evaluated evidence of the effects of human disturbance in the Tapajos National Forest and its surroundings using physicochemical and biological variables in surface waters as indicators. In order to accomplish this, we first analyzed the data series of precipitation in the region. Samples were collected from the Tapajos River in areas influenced by land use and occupation. We made on-site assessments and collected samples for laboratory analysis. Rainfall in December 2012 was higher than the climatology indicated. The results of the Water Quality Index (WQI) indicated the predominance of the "good" to "great"; its values ranged between 70 < WQI < 90 and 90 < WQI < 100, in 70.0 % of the samples collected. The balnearies Alter do Chão and Pindobal had the highest levels of fecal coliform, possibly due to anthropogenic effects that could be mitigated by adequate tourist practices. The highest WQI and greater transparency of the water near Tauari, showed minimal effects of human activities in nearby surface waters. It is concluded that water bodies are sensitive to changes in land use and those changes may threaten the maintenance of conservation areas.
conservation unit; water quality