4.2.2 Suspended Solids
As for suspended solids, the highest values were recorded in T1
treatment (Figure 3C) compared to T2 (Figure 3D), in February all values
were bigger than 100 mg l-1 (milligrams per litre), with an average of
252 mg l-1 for that month. The same happened with the values of
October 222 mg l-1 and in December with an average of 416 mg l-1. In T2,
the values were more uniform, with averages of 126, 163 and 107 mg
l-1, only with a peak of 696 mg l-1 observed in October 2012 (Figure
3D), however, it was still below the peaks recorded in the T1 in October
2006, which was 884 mg l-1 and the peak observed in December 2003 with
1850 mg l-1 (Figure 3C).
The results of suspended solids for the rainy season were lower than
those described by Setzer (1985) who evaluated soil losses and their
relation to turbidity and water parameters in several watershed in the
state of São Paulo and inferred that the averages annual rates for
suspended solids in the rivers of São Paulo are slightly less than 150
mg l-1, rising to almost 300 mg l-1 in the rainiest months and lowering
to less than 50 mg l-1 in the driest months.
The results of the work show that there was a significant decrease in
suspended solids after the adoption of conservationist practices and the
rehabilitation of agricultural properties. Rodrigues et al. (2015)
evaluated that the runoff coefficient was low in the presence of
vegetation resulting in bigger infiltration and better flow regularity
and that erosion and carried sediments increased on unprotected soils,
changing the dynamics of water on the soil.