Resumo

RAMIREZ R., John J.. Daily and seasonal behavior of optical and thermical structures in a Colombian tropical reservoir (La Fe reservoir). Rev. acad. colomb. cienc. exact. fis. nat. [online]. 2015, vol.39, n.150, pp.77-90. ISSN 0370-3908.

The objective of this research was to find out about the temporal variation of optical and thermal structures in La Fe dam both in daily and seasonal scales. Our hypothesis on the optical structure was that there would be little variation in both time scales. As for the thermal structure, we predicted that it would vary more on a daily basis that in the seasonal scale. In order to corroborate these assumptions, we took ten nictemeral samples in the water column of the dam at four hour intervals during 10 months (December 2002 to November 2003). We evaluated the following variables: air and water temperature, wind direction and speed, Secchi depth, mixing depth, apparent color and turbidity, and profiles of electrical conductivity, dissolved oxygen, total CO₂ and pH. The optical shape presented slightly significant differences on the daily scale and non-significant differences in the seasonal scale. Given its intense color, littoral belt of Egeria densa, algal blooms, allochthonous inputs, and the atelomictic pattern of the system, its shape may be considered as being a GA type. As the wind didn't work long enough to destabilize the water column, it remained stratified all along the sampling period and mixture was present only in the first few meters as can be expected in an atelomictic reservoir in which the mixture is mainly due to convective forces. Consequently, bottom temperature varied very little, the pH profile tended to decrease, and the electrical conductivity and total CO₂ to increase.

Palavras-chave : Tropical dam; optical and thermal structures; diurnal and seasonal dynamics.

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