A recent story in the LA Times, China moving heaven and earth to bring water to Beijing, describes the Chinese massive water works project to bring water from the wet south to the dry north. It’s called the South-to-North Water Diversion. It’s pointless for me to regurgitate the LA Times article, but it is important to realize the scale of the project. It’s right up there with The Great Wall. $62 billion, three aqueduct branches totaling over 1,500 miles, hundreds of thousands of humans displaced, and 44.8 billion cubic meters of water diverted every year. In other words, the largest project of its kind in the history of mankind.
The reason is simple. The population of China is growing, and so are their cities. Beijing and the other cities in the north need drinking water. The Yellow river is too polluted, the Grand Canal is being used for agriculture, and groundwater is depleted. The Gobi desert is encroaching Beijing because of irresponsible groundwater use, and in general, China is no good at managing their water supply. The Yangtze river in the south has lots of water, so why not build an aqueduct to divert it to the water starved north? It seems like a good idea at face value, but take a longer look at it and the reality begins to come into focus. For a period of time the project will provide relief, but it will not last. The prevailing criticism deals with degradation of river ecosystems, displacement of people, and disparity in who gets the water, but there is something much more profound for the Chinese to worry about. Continued desertification.
It’s well known that China has desertification problems. This means that once fertile land is literally drying up and turning into a desert. This happens for two major reasons and many smaller reasons. The first major reason is the depletion of groundwater. Groundwater is hydraulically connected to surface water so as the levels go down, surface water moves in to take its place. This causes levels of rivers and lakes to go down. Vegetation that once dipped its roots into groundwater begins to shrivel up. The soil erodes away easier destroying more vegetation. Over time, a desert takes shape. The second major reason is unsustainable development. Forests are cut, and land is paved. In the case of China, this is happening at a startling rate. As impervious area increases, less water makes it into the soil, thus less to recharge the groundwater aquifers. Imagine what happens to rain in a parking lot. It hits the ground and almost immediately gets piped away. Essentially, the rain is hitting the ground and instead of replenishing the local supply of water it is divereted directly into rivers that empty to the ocean. Will diverting billions of gallons of water to the north from the south solve this problem? Not likely. it may make it worse.
Growing areas, like Beijing, have a growing demand for water. This demand exceeds the supply to such an extent that desertification is taking place. Instead of coming to a halt, the growth continues and water scarcity begins. Once water is imported to these growing areas there is no reason to believe the growth will end. The growth has a momentum we’re all familiar with. Growth is considered healthy in our modern world. This is exactly what happened to Los Angeles. (In case you don’t know, LA imports its water from over 600 miles away.) Instead of limiting development due to lack of water, importing water gives the impression of abundance and therefore encourages more development which creates more impervious area. This new impervious area whisks away even more replenishing rainfall to the ocean. Also, once the demand meets the new supply, groundwater pumping will begin again further depleting the groundwater levels. Fast forward to Beijing 2100. Once again demand has exceeded the supply due to “healthy” growth and pumping of groundwater begins again. This time it’s even worse. More people, more groundwater pumping. More impervious area, more rainfall conveyed away to the ocean and even less to replenish the groundwater. The desert is created even faster than before the aqueduct. Water is more scarce than it was before the aqueduct. Not good.
Even if development was limited, which it won’t be, they are still exporting water from three separate watersheds belonging to branches of the Yangtze river. Exporting water from a watershed creates a desert of its own. This desertification is a bit easier to understand. You take away water then the vegetation dies, the groundwater levels go down, more vegetation dies, soil erodes and slowly but surely a desert emerges from once fertile land. Unfortunately when China is once again in a situation of rapid desertification and water supply scarcity they won’t have many options. What could they do instead?
In the modern developed world, water is brought to the city. Before modern conveyance, cities were brought to the water. When deserts formed or rivers changed course the city would move to a new water source. Hydrologists and others realize the problems associated with moving vast amounts of water from one watershed to another and their voice needs to be heard. China’s South to North Diversion, The largest water works project known to man, is not much more than a quick fix which will exasperate an already devastating problem in the long run. There are better solutions.
There isn’t one magic solution to China’s problem or any other water scarcity problem. The solution is complex and must involve an understanding that the current growth is unsustainable. The solution must begin with a hard look at the local water supplies, the hydrological cycles associated with each and what the carrying capacities of those cycles are. The solution may involve limiting growth in some areas, encouraging growth in others. It may involve conservation measures and groundwater balance measures. It may involve rainwater harvesting and minimizing impervious areas. There are so many things that could be done that won’t be done. I sincerely hope that when the United States finds itself in a similar position we listen to the hydrologists and other water scientists and make the right decisions. Don’t think it will happen here? That’s another article. Water is the essence of life and we need to protect it.
Its All One Big Adventure 