Hidrogeochemical comparative study of the Ja and Jacar-Guau River watersheds, So Paulo, Brazil

The main subject of the present work was to carry out a hydrochemistry comparative study between two river basins in Sao Paulo State: the Jacare-Guacu Basin (21°37'-22°22'S and 47°43'-48°57'W) and the Jau Basin (22°09'-22°28'S and 48°16'-48°47'W). Nine sampling points in the Jacare-Guacu River and eight in the Jau River were established. The water sampling was performed once each two months from March/95 to September/95. The following variables were analyzed: temperature (°C), pH, conductivity (mScm¾1), dissolved oxygen (mg/L) and ionic water composition. Comparatively the Jau River showed higher spatial variability, less oxygenated water and higher mineralization, due to high pedological and geological substrate richness, point sources existence and less riparian forests. The Jacare-Guacu River showed less spatial variability, more oxygenated water with lower ionic concentration due to the lower geological and pedological watershed richness, absence of pollution from point sources and higher riparian forest protection.