Abstract
This study evaluated the trophic conditions of the reservoir located in the urban perimeter of the town General Sampaio, semiarid region of the Ceara State, Brazil and its relationship with seasonal variation in rainfall between 2010 and 2011. It was obtained data for Secchi disk transparency, total phosphorus, and chlorophyll a to calculate the Trophic State Index (TSI), as well as rainfall data. The Trophic State Index (TSI) proposed by Carlson (1977) and modified by Toledo Junior (1990) was used to test the influence of the seasonal variation in rainfall on hydrological variables and on trophic conditions of the reservoir in 2010 and 2011. There was seasonal variability in variables analyzed between climatic periods (rainy and dry) and trophic conditions determined through the trophic index indicated conditions ranging from oligotrophic to eutrophic during the two years analyzed in this reservoir. Under these circumstances, one may conclude that the trophic status is related to seasonal fluctuations in the hydrology of the system controlled by rainfall, which is a common feature of semiarid regions.
Highlights
Large reservoirs have a horizontal spatial distribution and temporal fluctuations, with their own dynamics, balancing the input/output (TUNDISI et al, 2004)
According to Blenckner (2005), the seasonal distribution of limnological variables in a reservoir is related to the following factors: i) advection flows generated by the entrance of rivers caused by rainfall; ii) streams due to the horizontal flow, consequence of water
Temporal fluctuations generated by seasonal variations in rainfall lead chemical, physical and biological modifications in the reservoir water (TUNDISI et al, 2004)
Summary
Large reservoirs have a horizontal spatial distribution and temporal fluctuations, with their own dynamics, balancing the input/output (TUNDISI et al, 2004). These authors have reported a temporary compartmentalization depending on the horizontal flow in the surface. It is influenced by the distribution of water masses with different densities and wind action. Biological Sciences masses outflow at several depths and iii) surface flows due to seasonal wind action. Temporal fluctuations generated by seasonal variations in rainfall lead chemical, physical and biological modifications in the reservoir water (TUNDISI et al, 2004)
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