The theme of this article are hydronyms which can be explained by chronologically earlier names: first of all by the names of towns and villages and less often by the primary forms of water names. The author presents two types of relations between water names and place names. The first group includes the hydronyms identical with place names; the second the hydronyms derived from water names with simple structure (generally, although not exclusively, from older names of these formations) or from the names of places where these water bodies are situated. The last group is most frequent. Here, one can find, first of all, the derivatives with the suffix '-ka' (as well as '-anka') and rather rarely adjectival formatives '-n-' and '-sk-'. The suffix '-(an)ka' in newly created names has two functions: diminutive one and, first of all, the structural one.