The exponential growth of industry and population around
some of China’s central cities on the plains upriver from Xian meant that
age-old flooding and drainage problems were getting worse whilst a constant
water supply could never be sufficient.
So, back in the early part of this century it became necessary to find
ways to engineer the drainage, and also find some way to capture water on the
rainy south side of the Quinling Mountains and deliver it in a steady flow to
the north side.
The World Bank were asked to finance the drainage scheme …
and their preliminary report was a kind of geography lesson …
The bright idea that followed was to locate exactly the right point on the south side of the mountains where the most water flowing off the south side of the Qinling Mountains could be gathered from the upper part of the Hanjiang River system, and then to deliver all of it through one huge and more or less horizontal tunnel, back under the mountains to the area where the plains of the Weihe River and the Yellow River merge.
It turned out that the mountains were incredibly hard and
brittle as well as being waterlogged and so the tunnelling was fraught with
danger and it took thirteen years.
Here’s the news footage that celebrated the tunnel’s completion.
https://www.seetao.com/details/140235.html
And here's a sanitized view of working conditions for the labourers ...
https://www.chinadaily.com.cn/a/202102/20/WS60307896a31024ad0baa9e77.html
