Influência de eventos hidrológicos extremos na qualidade da água de reservatórios na região tropical semiárida
2015
Reservoirs are artificial ecosystems, intermediate between rivers and lakes, with
diferent morphological and hydrological characteristics that can provide many important
benefits to society. However, the use of this water for human consumption, watering livestock,
leisure, irrigated agricultural production and pisciculture development, directly influence the
increase loading of nutrients to aquatic environments and contribute to acceleration of
eutrophication. Furthermore, global climate models are predicting a higher occurrence of
extreme events such as floods and severe droughts, which will create hydrological stresses in
lakes. In the semiarid northeast we can see the occurrence of these events, the drought of the
years 2012, 2013 and 2014 was the worst drought in 60 years, according to the National Water
Agency (ANA). Thus, this study aimed to evaluate the quality of the semiarid tropical water
sources, identifying temporal patterns in periods with extreme hydrological events (floods and
severe droughts). The study results showed that Gargalheiras and Cruzeta reservoirs presented
significative changes in the limnological variables between rain and severe drought periods,
with better appearance and in the most of the water quality variables in the rainy season and
higher nutrientes concentrations and high electrical conductivity values in severe season,
indicating decay of its quality. However, we found diferent behaviors between the reservoirs in
severe drought. While Gargalheiras showed a typical behavior of the region, with high
concentrations of algal biomass, indicating the worsening eutrophication, Cruzeta demonstrated
a colapse in the total phytoplankton biomass, evidenced by the decrease in chla concentrations.
This fact occurred because the low depth and proximity with the sediment facilited the inorganic
solids resuspension and, consequently, resulted in turbid water column and light by limitation.
In addition, the different behaviors between the reservoirs indicate that the responses of these
environments problems such as extreme events must take into account factors such the region
climate, size, depth of the reservoir and the basin characteristics.
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