Chu River

From the Naryn Region, the Chu River travels along the eastern border of the Kyrgyz Range, via the Boom Gorge, past Bishkek, and into Kazakhstan's deserts. The river is said to come out of Issyk-Kul, however it really travels through the highlands, missing the lake by many kilometers (though water from the lake may feed the river through deep underground passages).

The Chu River, as well as other rivers that run through the region, water the valley surrounding Bishkek extensively. The water pollution index of the Chu River in the Chu Valley varied from 0.25 to 0.7 units in 2004–08, according to the Kyrgyz State Agency for Hydrometeorology, indicating Class II contamination. The lone exception was a monitoring station downstream of Vasilyevka hamlet, where the water pollution index varied from 0.4 to 1.2 units and the water quality was rated Class II(Clean)/Class III.

According to Kazakhstan Hydrometeorological Service (Kazhydromet), the Shu (Chu) River in Kazakhstan's Jambyl Region had a water pollution index of 2.01 (Class III, "Moderately contaminated") in 2008 and 1.83 (Class III, "Moderately polluted") in 2009. Biochemical oxygen demand, nitrites, copper, and phenols all surpassed the maximum permitted quantities in the water.

Length: 221 km