The flow of the Chang Jiang is some 20 times greater than that of the Huang He. As much of 40% of China's total grain production, 70% of rice output, and more than 40% of the population are associated with the Chang Jiang's vast basin that includes more than 3,000 tributaries. With its numerous tributaries, the Chang Jiang drains nearly 20% of China's total area. Its upper reaches tap the uplands of the Tibetan Plateau before sweeping across the enormous and agriculturally productive Sichuan Basin that supports nearly 10% of China's total population. It is in the middle course of the Chang Jiang that the controversial Three Gorges Dam is being constructed.