Unit U2: Water Management Without a Dam

The Min river comes off the mountains carrying a great deal of water and gravel. A long artificial spit called the fish mouth splits the river in two and sends a controlled share into an inner channel. A low weir beside it lets excess water and sediment spill back into the outer channel, and a narrow cut through a spur meters what finally reaches the plain. Each piece solves the problem the previous one creates.

A dam silts up and eventually has to be replaced. This system sheds its silt by design and needs annual maintenance, summed up in a six-character rule attributed to Li Bing: dig the bed deep, keep the banks low. The PreeChina page on Mount Qingcheng and Dujiangyan gives the full account.

1. Measure how the flow divides between the inner and outer channels.
2. Draw the water path from the fish mouth to the plain.
3. Argue the design against a modern dam: silt, maintenance, cost of failure.
4. Keep a log of the day: place, weather, what was measured, what was learned.

• IB DP Environmental Systems and Societies (water)
• IB DP Geography
• AP Environmental Science
• A-Level Geography, through the water and landform units

The school's coordinator confirms the fit against the current course documents.

Dujiangyan lies about sixty kilometres north-west of Chengdu, so it takes a morning or an afternoon of a Chengdu leg. See School Trip to Chengdu. No PreeChina student group has done this unit on site yet.

Fees follow the length of the whole trip, for groups of 10 or more (10 included): USD 100 per person for trips of up to 10 days, USD 150 for 11 to 20 days, and an individual quote beyond 20 days. Hotels, meals, transport, tickets and other trip expenses are separate unless the agreed quotation says otherwise. See the cost page.

Is a dam comparison part of the unit?

Yes. Students argue the Dujiangyan design against a modern dam as their final task.

Which courses does the unit connect to?

IB DP Environmental Systems and Societies, IB DP Geography and AP Environmental Science.