author = "Santos, Jana{\'{\i}}na A. and Marins, Rozane V. and Aguiar, 
                         Jos{\'e} E. and Chalar, Guillermo and Silva, Francisco de Assis 
                         Tavares Ferreira da and Lacerda, Luiz D.",
          affiliation = "{Universidade Federal do Cear{\'a} (UFC)} and {Universidade 
                         Federal do Cear{\'a} (UFC)} and {Universidade Federal do 
                         Cear{\'a} (UFC)} and {Universidad de la Republica} and {Instituto 
                         Nacional de Pesquisas Espaciais (INPE)} and {Universidade Federal 
                         do Cear{\'a} (UFC)}",
                title = "Hydrochemistry and trophic state change in a large reservoir in 
                         the Brazilian northeast region under intense drought conditions",
              journal = "Journal of Limnology",
                 year = "2017",
               volume = "76",
               number = "1",
                pages = "41--51",
             keywords = "Reservoir, semiarid, trophic state index, eutrophication.",
             abstract = "The study shows changes on physical and chemical water parameters 
                         and of trophic state in a large reservoir in the Brazilian 
                         semiarid region following decreasing reservoir volume due to 
                         rainfall shortage during four consecutive years. The monitoring 
                         period, between November 2011 and May 2014, assessed approximately 
                         50% water volume reduction and 10 meters' decrease of reservoir 
                         water level that degraded water quality. Decrease in reservoir 
                         volume, strong evaporation and the permanent influence of 
                         anthropogenic activities, favored the concentration of salts and 
                         accumulation of nutrients and of increasing pH. Thermal 
                         stratification of the water column occurred when volume was 
                         maximum and lead to a significant reduction in dissolved oxygen in 
                         the hypolimnion (0.07 to 2.62 mg L-1). Diminishing volume resulted 
                         in mixing of the hypolimnion nutrient-rich and oxygen-poor waters 
                         in the entre water column and changed the initial oligotrophic 
                         condition to eutrophic. However, the temporal scale of the 
                         response of the reservoir's trophic state differs in the different 
                         areas of the reservoir. Whereas deeper areas accumulating 
                         nutrients from aquaculture and agriculture progressively became 
                         mesotrophic and eventually eutrophic; shallower regions far from 
                         direct anthropogenic influences, changed their trophic sate much 
                         later, but rapidly turned into super-eutrophic conditions, 
                         probably due to more intense sediment resuspension and water 
                         mixing. Trophic State Index followed nutrient increase during most 
                         of the period. However, it also responded to an increase in 
                         chlorophyll a concentrations when the reservoir achieved its 
                         minimum volume, in particular in the shallower areas. The results 
                         suggest that this type of reservoir systems are vulnerable to 
                         eutrophication during extended drought periods and that a better 
                         assessment of the maximum support capacity for reservoir 
                         activities, particularly aquaculture, must be re-assessed taking 
                         into consideration worst case scenarios forecasted by global 
                         climate change.",
                  doi = "10.4081/jlimnol.2016.1433",
                  url = "http://dx.doi.org/10.4081/jlimnol.2016.1433",
                 issn = "1129-5767",
             language = "en",
           targetfile = "hydrochemistry.pdf",
        urlaccessdate = "14 abr. 2021"