Towards the northeastern side, we find tributaries of numerous rivers formed by the glacial melting of the eastern side of Cordillera Blanca. Here, there are small streams which will irrigate neighboring valleys and will eventually contribute water to Marañon in its medium to high course.
On the central side of the mountain range area, the Santa River is the main body of water that follows the predominant direction (SE-NW) towards the Pacific basin, after crossing Cordillera Negra and forming an impressive fault known as Cañon del Pato. The Santa River emerges with this name from Lake Yanacocha, a tributary of Lake Conococha located at 4,020 m.a.s.l. (13,185 ft) gradually becoming deeper. The amount of water increases and becomes more turbulent after emerging from the western side of Cordillera Blanca. In addition, the Santa receives contributions from many valleys, which like delicate capillaries, drain water from beautiful, important lakes located at the foot of snowcapped mountains. The great contrast in the location of this natural resource (between the western side of Cordillera Blanca and the eastern of Cordillera Negra) is due to two reasons: the first is that the scarce watery mirrors present in the highlands of Cordillera Negra are found to the west of the water divider. The second is that the behavior of the water currents that cross the valleys towards the Santa River depends upon seasonal rains, making the water flow rather irregular.