The Iser, Bober, Aupa, Zacken, Queiss, and a great number of smaller streams also rise among these mountains or on their skirts; and small lakes and tarns are not unfrequent in the valleys.
A little above Brandeis it picks up the Iser, which, like itself, comes down from the Riesengebirge, and at Melnik it has its stream more than doubled in volume by the Moldau, a river which winds northwards through the heart of Bohemia in a sinuous, trough-like channel carved through the plateaux.
The Iser rises among the mountains on the south.
Bohemia belongs to the watershed of the Elbe, which rises within the territory and receives on the right the Iser and the Polzen, and on the left the Adler; the Eger with its affluent the Tepl; the Biela and the Moldau.
Its principal affluents are the Adler, Iser and Eger, and, most important of all, the Moldau.