The Kninsko polje, or Knin field, is the richest in water, with the spring of the Krka River at its edge, in a cave just under the Topoljski slap waterfall, at an altitude of 224 m.
The Krka River basin is made up of the basins of the Butišnica, Krčić, Kosovčica, Orašnica, Čikola, and Guduča Rivers as well as the basin of the Krka River, which is spatially the largest. In addition to these waters, the Krka River basin includes the waters of the sinkholes southeast of Grahovo in Bosnia and Herzegovina and the subterranean waters of the upstream reaches of the Vrba River valley, a tributary of the Čikola River.
There are three types of areas within the Krka River basin: mountains, fields and plateaus. The mountain region includes the northeastern part of the upper course of the Krka River. The fields include the middle course of the river, with four large fields: Plavno, Kninsko Polje, Kosovo Polje and Petrovo Polje. Kninsko Polje, or Knin Field, is richest in water, with the spring of the Krka River at its edge, in a cave under the Topoljski slap waterfall, at an altitude of 224 m.
The Krka River receives the majority of its tributaries in the first 4 km of its course, still in the Kninsko Polje. The first larger left tributary is the Kosovčica, and right tributary is the Orašnica. Downstream, after leaving Kninsko Polje, the Krka receives its richest tributary, the Butišnica. The Čikola River flows through Petrovo Polje, and becomes the final tributary of the freshwater part of the Krka River, draining just above Skradinski buk.
In the canyon part of the Krka River, the largest tributaries are Miljacka and Jaruga, while the Torak spring is an important tributary in the Čikola River canyon. The Miljacka spring, on the right bank of the Krka River, is a direct connection between the Zrmanja River and the Krka River, and is a unique hydrogeological phenomenon.
Downstream of Skradinski buk, the Krka River is under a maritime influence, and its springs are brackish. The only significant tributary in the lower, submerged part of the mouth of the Krka River is the Guduča River.