Wang Kaiping, a 54-year-old restaurant owner in Yibin, Sichuan province, sells 4,000 to 5,000 bowls of iced cake made of glutinous rice a day.

Despite the summer heat, lots of tourists visit Yibin, the first city on the upper reaches of the Yangtze River, and many try the iced cake, a famous local snack.

According to Hu Xiaoping, an information officer with the Yibin government, the huge influx of tourists has much to do with the environmental upgrades in the city.

A decade ago, many ships serving as restaurants were anchored in the Yibin section of the Yangtze River, polluting the river with its litter. Sand dredgers wrought havoc, and shanties on both sides of the river discharged sewage directly into the water.

The city has spent nearly 10 years relocating shanty residents and banning the sand dredgers and ship restaurants, Hu said.

After relocating nearly 2,000 households in 2013, the city restored nearly 67 hectares of land to build Yangtze Park.

The park, costing nearly 600 million yuan ($87 million), has attracted a daily average of over 10,000 tourists - nearly 100,000 people on a peak day - since it opened in 2015.

Environmental upgrading has drawn not only tourists but also Wang, the iced cake seller.

"My daughter and I were migrant workers in Guangzhou, Guangdong province. When we saw many tourists in our home city, we returned to sell iced cakes," Wang said. "It is nice to work at home, and we can earn about 300,000 yuan a year."

Each bowl of iced cake is sold for 2 yuan, and I earn much more than I did when I was a migrant worker in Guangzhou, she said.

To build an ecological screen on the upper reaches of the Yangtze, Sichuan stresses protection of both the river and its tributaries.

Minjiang, an important tributary of the Yangtze, flows through Meishan, which has witnessed booming economic development in recent years. Although Meishan is only a small city, 32 of the Fortune 500 firms have settled there.

The city requires all firms to be located in industrial parks to ensure centralized treatment of sewage, providing 10 square meters of wetland for each ton of sewage to ensure it can be further treated, according to Wu Haijun, an information officer with the Meishan government.

Sichuan has resorted to legislation to protect the tributaries of the Yangtze. The Regulations on Water Environment Protection of the Tuojiang River Basin, which will come into effect on Sept 1, is meant to safeguard the basin's water environment.

The basin, a core area of the ecological screen in the upper reaches of the Yangtze, boasts more than 25 percent of Sichuan's population and 30 percent of its GDP. But it is also Sichuan's most polluted river, said Hou Xiaochun, deputy head of the Standing Committee of the Sichuan Provincial People's Congress.