Waters from dams, rivers, creeks, and deep and shallow wells in an area of 3370 km2 around Iguatu (Ceará) have been analyzed. Samples were taken in January and August 1978 from a total of 35 locations. Carbon-14 ages of deep wells range from about 17 000 years to modern with seasonal variations, indicating a mixture of a deep old component with modern waters. This conclusion is confirm ed by the 18O results. Shallow wells show a strong rainwater influence. The chemical character of waters from wells is the same as that of the Orós dam. A classification of suitability for domestic use and irrigation is given.Waters from dams, rivers, creeks, and deep and shallow wells in an area of 3370 km2 around Iguatu (Ceará) have been analyzed. Samples were taken in January and August 1978 from a total of 35 locations. Carbon-14 ages of deep wells range from about 17 000 years to modern with seasonal variations, indicating a mixture of a deep old component with modern waters. This conclusion is confirm ed by the 18O results. Shallow wells show a strong rainwater influence. The chemical character of waters from wells is the same as that of the Orós dam. A classification of suitability for domestic use and irrigation is given.