This network of rivers and aqueducts are fed by reservoirs to the north of the city. The Miyun Reservoir, the largest in the municipality, is created at the confluence of the Chao and Bai Rivers, which forms the Chaobai. The Yongding, before entering the municipality in Mentougou District, is dammed to create the vast Guanting Reservoir of Hebei Province. Despite these reservoirs, the city of Beijing faces chronic water shortages due to water-intensive agriculture, industry, and population growth. Under the South-North Water Transfer Project, the city plans to draw water from the Yangtze River through the Grand Canal, which was built 800 years ago for transportation, but now is being upgraded into a major aqueduct.