Water temperature variations during one year in a small lake at Piracicaba - SP, Brazil

Abstract

Thermal variations of water at four depths (0.10; 0.30; 0.60 and 1.20 m) in a small lake of the Piracicaba county, São Paulo State, Brazil, were measured during the period of August 1978 to August 1988, as a subsidy to the aquaculture and the husbandry of amphibia in captivity. During a day, the thermal fluctuations of water were small, independently of the air temperature amplitude; in the daytime fluctuations were greater at the depths of 0.10 and 0.30 m, mainly in the period August-January. In clear days the temperature of water was greater than that of the air in most of the day, while in cast or rainny days this fact occurred all day. Consequently, daily mean temperatures of water at the four depths of measurement were greater than the daily mean air temperatures, except for a few days. Thermal stratification was more pronounced in the period August-January. The relationships between thermal fluctuations of water and meteorological elements are discussed, and the daily and annual absolute minimum and maximum temperatures of water are presented.