In a new book, a geographer-hydrologist examines in detail the problems of the Crimean yails associated with their karsting and the possibility of their afforestation. The rivers flowing from the Yailin mountain ranges and the possibility of improving their water regime through forest plantations on the Yailin plateaus are characterized. The recent problem of deterioration of the ecological state of the yail is mentioned. The text is accompanied by photographs, maps and graphs.