It is dry here in Baja. You may have noticed that all plants in my photos are cacti. I have not worried once about rain, and Baja’s cities average below 10 inches of rain per year. Where does the water come from that flushes the toilets in these firehouses?

   In southern Baja, almost all the water comes from underground aquifers. Two locals, Daniel and Fernando, drove me around La Paz yesterday and showed me where pipes go many tens of meters beneath the ground to find freshwater. Pipes also lead out of the town, where they draw underground water from farther away. In Ciudad de Constitución, where I was a few days earlier, the corn fields and grapefruit orchards also get their water from underground. The goat that I watched get slaughtered ate alfalfa watered from this source. Loreto, where I spent Christmas night, also relies on underground water.

    All these water sources sit close to the ocean, and, somewhere beneath the ground, there is a boundary between ocean saltwater and freshwater. If water is pumped faster than rain recharges it, saltwater gradually creeps landward, and, eventually, the well draws saltwater and becomes unusable, a common phenomenon known as salt water intrusion. This has already happened to a number of wells in La Paz, as well as all the wells in Loreto. Loreto now pumps all of its water from a valley far away.

    With climate change, the ocean is going to rise due to the melting of glaciers as well as the fact that water expands when warmer. It is expected that with a 2 to 3 degree Celsius warming this century, the ocean’s surface will likely rise half a meter this century, and much more in the following centuries (the rising oceans will be another entry here). If the ocean level is higher, the underground boundary between salt and freshwater will move inland, increasing the risk of salt water intrusions. Also, in a warmer earth, the crops near Ciudad de Constituión will require more water because evaporation will increase, thus requiring more water to be drawn from beneath the surface.

    But, with a changing climate, you may say, there might be more rainfall. This is possible. The climate models are not good at predicting future rainfall, especially on a scale as small as Baja California. For the general region of Central America and Mexico, however, the models seem to show, in general, a decrease in precipitation toward the end of the century. More likely, we will see more extremes — both more droughts and more floods, making it more difficult to predict water resources from year to year.

    Unfortunately, the water sources of Baja will probably be subject to overuse long before climate change has a large effect. It seems that the water is already being used unsustainably — one study shows that Loreto has only a few years left on its second aquifer before the water runs out. And the population is growing rapidly. Whether it is second homes in Loreto for foreigners or a huge influx of people from the Mexico mainland to La Paz, the population growth will result in need for more water. Cabos San Lucas, the town on the southern tip of the peninsula (which I am not visiting), already has an expensive desalination plant to provide water for visiting tourists. Factors other than climate change currently have a much bigger effect on Baja’s water, and these problems need to be addressed now. It is likely that people are simply wasting water and not paying the full price of water. Nonetheless, climate change will only worsen the problem.

    While it may be economic to run desalination plants for tourists, it is unclear how the people of La Paz, and especially its poorer citizens, will fair once they have to pay for water. It is also unlikely that agriculture will be economic with expensive water. I wonder what the future of Ciudad de Constitución, a city built on agriculture and not tourism, will be once the wells turn salty. I wonder if future cyclists will see goats at the roadside or enjoy fresh grapefruits. And, to read more about climate change and agriculture, you will have to wait until later in Mexico….

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