Within the wetlands of the semiarid region of Central Chile, The Yali wetlands complex is the most important because it is protected as a RAMSAR's wetland. However, information about their hydro-geomorphological characteristics is almost non existent. In this study, the hydrochemical characteristics of 20 sampling sites, surveyed in July 2008 and which include coastal lagoons, estuaries, streams, saltmarshes, and reservoirs, were analyzed. The hydrochemical complexity stands out in relation to the water salinity (range = 320 - 58 800 mu S/cm) and ionic composition of the studied wetlands in relation to the relative importance of the dominant water flow that sustains these wetlands. In relation to trophic state, most of the studied wetland systems are eutrophic or hypertrophic (medium values for total nitrogen = 4.7 mg/l; and soluble reactive phosphorus = 0.4 mg/l) due to the existing use of land (eucalyptus forests, cattle farms and wastewater inputs).