Hydrographic basin

1. The area between watersheds traversed by a main river and its tributaries. From an institutional perspective, the administration of this area falls to the River Basin Authorities. 2. For the purposes of Royal Legislative Decree 1/2001, of July 20, a river basin is defined as “the area of land whose surface runoff flows entirely through a series of streams, rivers, and possibly lakes to the sea through a single mouth, estuary, or delta. The river basin, as a resource management unit, is considered indivisible.”.