of the Cuzco Valley, Peru. 



13 



supplied from springs in the limestone gorges; the western 

 branches within this area contribute little. Within the city 

 of Cuzco the Huatanay receives two canalized tributaries, 

 Chunchullumayo 5 and Tullumayo, 6 which have played a prom- 

 inent part in the history of the city. The Chunchullumayo 

 receives its 'small perennial supply from a network of branches 



Fig. 7. 



Fig. 7. Oropesa Basin. View looking east from a point on the cliffs 

 at Angostura Narrows. 



issuing from glaciated valleys floored with till and occupied 

 by swamps. In its lower course along the border of the Cuzco 

 gravel fan the stream is supplied directly by ground water 

 which makes good in part for the loss from irrigation ditches. 

 During October 18 springs and seeps, many of them accom- 

 panied by landslides, were noted along the lower mile of the 

 Chunchullumayo, and it is probable that more than half of the 



5 The local name for the stream formed by the union of Rio Qquilque, 

 Rio Sipaspucyo and Rio Ayahuaycco. 



6 The lower portion of Rio Choqquechaca. 



