What I Do

A friend sent me an article today that described how many of the world’s major cities are sinking due to pumping of water from the ground under them. He asked if this was related to the work I do. This got me thinking. I wonder how many of my friends actually know what I do, or what a hydrogeologist does? So, I’ve posted my response to him in hopes of shedding a little light on the subject.
(For those of you that I know through work, please feel free to ignore this and head over to the Comedy Central site to watch video clips from the Daily Show.)

Subsidence is only a symptom of a much greater problem. The world today is facing a shortage of fresh water, and we as humans aren't going about addressing this crisis in a very intelligent fashion.
The above photo is from the San Joaquin Valley in California, and is quite famous amongst we hydrogeology types. It shows the elevation of the valley surface at various times over the last century. It's an incredible change to the area's topography in a very short time period.
The reason for this rapid subsidence is groundwater pumping. Downhole water pumps were only invented a little over a century ago. Before that, our choices were to lower a bucket down a well, or use surface water. As a result, we tended to live and farm where there was plenty of surface water.
Downhole pumps revolutionized how we manage (or mismanage) our water resources. They were initially used for agricultural irrigation, enabling crops to be grown in previously unsuitable locations. (I've got a great idea. Let's grow cotton in the desert!) The volume of pumping carried out far surpasses the natural recharge and we end up with dropping water tables.
That's the story of the inland valleys in California. They have pumped down the water table so far that the ground compacts, thus subsidence like in the picture above. Imagine that kind of subsidence in an urban area, and you see how various cities around the world are "sinking". It's potentially devastating, because the subsidence tends to be very uneven, resulting in buildings toppling over and so on.
Now, groundwater pumping isn't necessarily responsible for all of the "sinking cities" discussed in the article. Many of those cities are coastal, and are at least partially built on mud flats. For example, New Orleans was sinking while they were building it. (Who would build a city on a muddy delta below sea level anyway?) And Venice has been sinking for centuries, long before we knew how to get water out of the ground with anything but a bucket.
However, in many cases subsidence is still a striking indication of how our use of fresh water is out of balance. We're using far more than nature can replenish.
And, there's a lot more to it than just pumping of groundwater. Man has created other complicating issues, only one of which is dams. In feeding our ever increasing energy needs, dams have been constructed on almost every major waterway in the world. Dams prevent flooding and restrict water flow; both crucial to the natural recharge process. Dams, water rights and groundwater pumping are why today the rivers in Los Angeles are made of sand.
The bottom line is simply that there's not enough fresh water for the earth's population unless we drastically change our way of doing things. Even Canada isn't safe. Our water is primarily surface water that comes from glacial run off. Last I checked, the glaciers aren't going to be around for much longer. What then?
The US is experiencing a major population shift as more and more people move to the southwest. But how sustainable is that? There are no rivers to speak of in any of the southwestern states, and the supply of groundwater is diminishing at a rate that resembles George W's popularity rating. Yet, the southwest boasts the 5th largest population center in the US (Phoenix), and the fastest growing city in the US (Las Vegas). Both are located in the middle of the desert for crying out loud! So, not only do we have a shortage of water, but we're further complicating the problem by setting up shop in places where there really is no water in the first place.
From sinking cities to population shifts and global warming - it's all connected to fresh water, our most precious resource. Trying to manage the world's water is an incredibly complicated task. But hey, if it wasn't complicated, I wouldn't have a job!