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Of the numerous hydrogeochemical river‐water transformations provoked by intense and irrational soil practices, heavy metal contamination by agrochemical usage is the most worrisome. Long‐term metal accumulation can be transported by rainwater, during storms, contaminating rivers. Data on this type of contamination are still scarce, principally in developing countries, such as Brazil. This paper aims to evaluate the influence of agricultural activities on the hydrogeochemistry of the Paracatu River's sub‐basins.

From a total of 77 points along three sub‐basins, water samples were taken for heavy metal and trace element analyses using spectrometry of atomic emission through plasma (ICP‐OES, Spectro Ciros CCD). The principal water‐quality parameters, such as pH, turbidity, conductivity, oxi‐reduction potential, total dissolved solids (TDS), temperature and dissolved oxygen were measured in situ.

By incorporating a small drainage area at the monitoring points, it was possible to perceive agriculture's influence (in the form of heavy metal contamination from fertilizers and pesticides) on the water courses.

Although the research was carried out at a total of 77 points for water collection, data are from just one wet season, and need to be repeated.

The results demonstrate a need for monitoring the areas involved with agricultural activities, not only along the main river, but also along small streams that compose the Paracatu Basin.

There is no published literature on this subject regarding the three studied basins.

The purpose of this research was to identify the major environmental impacts occurring in Melo Creek, Minas Gerais, Brazil, especially as regards to its water quality.

Initial evaluation was based on aerial photograph interpretation. All the small creek catchments were delimited and 12 stream segments were chosen for sampling and analyses. The segments had their water discharge calculated and channel pattern described. Also determined for these segments were the physical and chemical parameters of the water, as well as the microbiological content. Both water and sediment samples were analyzed for metals and trace element quantification. Meanwhile, an environmental inquiry was conducted in all the small villages along the creek.

Data show a decrease in water discharge during the last decades, related to the increased destruction of the Atlantic Forest, especially at the riverheads and in permanent preservation areas (PPA). Most of the native vegetation was cut down to create farmlands and pasture. The water quality is also diminishing because for most of the properties, the main activities are pig raising and sugarcane liqueur production, which discharge their untreated effluents, along with domestic wastewater and sewage, directly into the creek. The results indicated that during its passage through the catchment, stream water became significantly contaminated with fecal coliform bacteria. As a consequence, the area possesses a high endemic disease index for water transmitted parasitism, especially for Schistosomiasis mansoni.

This was the first study done in the Melo catchment, a small rural basin without basic sanitation and with a highly prevalent schistosomiasis rate.