Pan evaporation rate was 2300–3700mmyear (Wen et al.,
2005). No perennial run-off originates from the area, and
the Heihe River has the only run-off flow through the area
(He and Zhao, 2006). The Heihe River, which originates
from the Qilian Mountain, flows through the Ejina Basin
and divides into two branches at Langxinshan (Wang,
1997). The two branches of the Heihe River flow into East
and West Juyan Lake, and the total length of these
branches in the basin are approximately 240 km