Wild Duck Lake National Wetland Park in suburban Beijing's Yanqing district is an essential stopover for migrating birds on the East Asia-Australasian Flyway. [Photo provided to China Daily]

The Guishui River has been diverted to supplement the marshlands. They, in turn, help purify the water on its way to the Guanting Reservoir.

Surrounding farmland has been reclaimed and hosts such water plants as reeds and bulrushes.

"It's important to raise public awareness of wetland protection and the fact that good ecology benefits humans," Liu says.

That's why management built the Wild Duck Lake Wetland Museum in 2007.

Exhibits of birds and plants, plus photos and videos, reveal how the wetlands change throughout the year.

About 20,000 primary and middle school students visit annually.

"Environmental protection is about action," Liu says.

"Students learn about the beauty of nature."

The best period to visit is between the reopening of the park and Tomb Sweeping Festival (mid-March to early April).

Visitors must follow such rules as staying on designated paths and out of fenced-off core zones, remaining quiet and refraining from barbecuing.