(Ecology of Jacaré Pepira River : Basin water major ions (São Paulo State of Brazil)

Abstract

The Jacaré Pepira River Basin is part of Paraná Basin which is the biggest hydrographic basin of Southern Brazil. It is located in the central part of São Paulo State in a region where the climate shows two seasons: warm and rainy where the climate shows two seasons: warm and rainy (October-March) and cold and dry (April-September). The basin area has 2,612 km and the main channel arises in the city of São Pedro, 960 m of altitude; after l74 km, the discharge occurs on Tiete River at approximately 400 m of altitude. A monthly study undertaken during two years (October/1978-September/1980) showed that Jacaré Pepira River water quality can be defined by median values of electrical conductivity (25.8 µS/cm) and ionic content (48.81 mg/L), distributed by 57.2 HC0₃, 21.0 Si, 5.2 Ca, 4.7 Cl, 3.4 Fe, 2.5 Mg, 2.4 K, 2.0 Na, 1.0 N-NH₃ and 0.3 N-NO₃ %. The major ions proportion showed the relation 42.0 Ca, 33.7 Mg, 14.3 Na and 9.7 K (%) to a total of 0.300 meq/L cations corresponding to 5.91 mg/L and 87.6 HCO₃, 12.4 Cl (%) to a total of 0.525 meq/L anions (30.31 mg/L). The method sensibility used was not enough to detect SO₄ ion. This paper discuss thus the relation between monovalent and divalent cations