Knowledge on hydrochemistry is very important to assess the quality of water for effective management of water resources or drainage water reuse. On this basis, an assessment of water quality was conducted in the Agoulinitsa district in Peloponnese (western Greece). Both drainage and irrigation channel water samples have been collected, treated, and subjected to chemical analysis. A characterization has been carried out using the Piper-trilinear diagram. Assessment of the water samples from the point of view of sodium adsorption ratio, Na(+)%, and residual sodium carbonate indicated that 60.0% and 83.3% of the drainage water samples during pre- and post-irrigation season, respectively, as well as the irrigation channel water samples, are chemically suitable for irrigation use. Moreover, assessment of the water samples by comparing quality parameters with the Food and Agriculture Organization guidelines indicated that 20.0% and 44.4% of the drainage water samples collected during pre- and post-irrigation season, respectively, as well as the irrigation channel water samples could cause slight to moderate problems to the plants. On the other hand, 80.0% and 55.6% of the drainage water samples collected during pre- and post-irrigation season, respectively, could cause immediate development of severe problems to the plants growth.