Seasonal quality changes in waters from Edson Queiroz dam, Acaraú basin, in the semiarid of Ceará.

Abstract

The Edson Queiroz Dam (251 hm3) is located in the Acaraú river basin of Ceará State, in the semi-arid Northeast of Brazil. During December 2002 to December 2003 monthly samples were taken for analyses of 18O, CE and Cl- in the water released for irrigation, captured at the bottom of the reservoir. After the rainfall period, a strong stratification has been observed caused by submerging recharge waters that are colder than those stored. Stratification persisted for about five months due to weak winds and reduced daily thermal amplitude during this season. Even though salinity (with maximum EC observed of 460 µS.cm-1) is low by regional standards, the phenomenon imposes a large amplitude on seasonal water quality changes for irrigation.