The Recharge Mechanisms in an Alluvial Aquifer Zone in Northeast Brazil

Abstract

Abstract The state government of Ceará has initiated a program of releasing water from dams in order to sustain a continual flow of water in the state's naturally intermittent rivers. However, river/ ground water connections in alluvial areas impose heavy losses on regulated discharges. Our study area, the “Ilha de Limoeiro” (Isle of Limoeiro), is located in the Lower Jaguaribe Basin and comprises an area of approximately 120 km 2 . We used environmental oxygen‐18 and deuterium, together with hydrochemistry, in order to identify the origin of ground water which is heavily exploited for intensive small‐scale irrigation in that part of the flood‐plain of the Jaguaribe River. This paper discusses the mechanisms of recharge for the different hydrogeologic systems: crystalline basement, thick alluvium, and alluvium/Agu.