This study investigates Arabic terms related to fresh water sources expressed in Oman's toponyms. It presents their classification and discusses the semantic and structural properties of both the place names and the hydrological lexicon. A description of oasis agriculture among the inhabitants is also given as necessary background for understanding the importance of locating water and its effect on landscape delimitation and categorization. In an environment without permanent water bodies, the significance of this resource is reflected in the way people conceptualize their landscape, minutely classifying its hydrological features and expressing them in toponyms. Historically, their knowledge of water sources has contributed to better land use management and sustainability of Oman's oasis agriculture.