Ob suši se Pivka pojavi med Prestrankom in Rakitnikom, pri Zagorju pa je podzemna kraška voda deset metrov pod dolinskim dnom presihajoče reke Pivke. Visoke vode se prelivajo na površje in napolnijo strugo reke Pivke, ki v takšnih razmerah teče površinsko od Zagorja do ponora v Postojnsko jamo. Ko se gladina podzemne vode dvigne, so poplavljene tudi plitve kraške kotanje – uvale in pojavi se več kot 15 presihajočih jezer. Ključne besede: kraško presihajoče jezero, uvala, Pivka, Slovenija. At dry season the Pivka river appears between Prestranek and Rakitnik while near Zagorje the underground karst waters are about ten meters below the valley bottom of periodical Pivka river. High waters pour over the surface and fill stream valley of the Pivka river, which runs continually from Zagorje to the ponor of Postojnska jama. When the level of the underground water increases, also shallow karst hollows – uvalas are fl ooded and changed into more than 15 periodical karst lakes.