永定河
The Guanting Dam on the Yongding River in the West is unable to provide drinking water to Beijing since 1997 because of pollution. However, the reservoir still provides water for irrigation and for industrial uses that do not require high water quality. The quality of the reservoir's water has improved slightly in the 2000s, when it was reclassified as class IV from class V of five water quality categories, I being the best and V being the worst. The government aims to improve the quality to class III.