Limnology of Borba Reservoir. Pindamonhangaba. SP. Brazil. I í Water quality

Abstract

The Ribeirão do Borba Reservoir is less than 4 m deep and is located at 22°55'55"S and 45°27'22"W, in the southeastern region of Brazil. The climate is tropical and shows only two climatic seasons: warm and rainy (October to March) and cold and dry (April to September). During one year, monthly samplings were carried out at two established stations. The water parameters were determined at the surface and bottom. The obtained values show that pH, electric conductivity, alkalinity and dissolved carbonic gas, bicarbonate, calcium, chloride, orthophosphate, nitrite and nitrate concentrations did not present any definite pattern of seasonality; other parameters, like transparency, increased in the cold and dry season, and temperature, color, turbidity and the concentration of oxygen, soluble silica, total iron, and ammonia in the water increased in the warm and rainy season. The Ribeirão do Borba Reservoir is a polymictic environment, where diurnal stratification is common in both climatic seasons. In relation to others reservoirs of the State of São Paulo, the studied reservoir shows, as a consequence of the localization in an agriculture area, a high trophic degree.