Urban, industrial and agricultural non-treated effluent discharges, as well as other sources of diffuse pollution resulting from the use of pesticides and fertilizers, create situations of eutrophication in the aquatic environment, which results in the deterioration of water quality and can lead to high toxicity levels.
In addition, the presence of livestock near watercourses leads to an increase in the levels of microbiologic pollution and increases in the suspended organic load in the water through the deposition of excrements and trampling of the riverbed sludge, further contributing to the reduction of water quality.
Pollution has its greatest impact on the least tolerant and most threatened species, like the saramugo, during the driest times of the year.
The deepest parts of watercourses are refuges used by many animal species and are particularly important for fish species that survive in them until the precipitation of the following year allows the reestablishment of surface runoff and the recolonization of other fluvial sectors.
