Qualidade de água em um reservatório na região semiárida

Abstract

Oros reservoir is the second largest in the state of Ceará and is used for human supply for the population of the Lower and Middle Jaguaribe and the Metropolitan Region of Fortaleza, besides being used for food production, aquaculture, tourism and irrigated fields. Due to the importance of this reservoir in the context of management of water resources in the state, this work aims to investigate the water quality of the reservoir to adapt an water quality index to the physical, chemical and biological conditions of the reservoir, and calculate the intake and balance of nutrients in its waters. The total period of study comprehended the months from April 2008 to December 2012, where water sampling were performed in a total of nine points in the reservoir, for monitoring of attributes pH, temperature, dissolved oxygen, biochemical oxygen demand, total phosphorus , nitrate, total suspended solids, turbidity and fecal coliform, to adapt the quality index, using principal component analysis; and seven points with monitoring of the concentrations of total nitrogen and total phosphorus to calculate balance and nutrient input. When obtaining adapted water quality index, it was concluded that the reservoir has water classified as regular to good quality and there is no effect of seasonality on water quality. With respect to intake and nutrient balance, the reservoir is storing the nutrients nitrogen (176 tonnes during the study period) and phosphorus (230 tonnes). Moreover, we could infer the same trend of intake of nutrients in the reservoir for both nutrientes and there was increase in the intake over time.