Passage: The main northwest part of the region is flat, a rarity in Kyrgyzstan. This is the valley of the Chu River. The valley's black soil is very fertile and is largely irrigated with water diverted from the Chu River. The region's Agricultural production includes wheat, maize, sugar beets, potatoes, lucerne, and various vegetables and fruits.

Question: Which body of water helps the land be so prolific?
Chu River