Mexico City and Salt Lake City share many similarities. Both are high-altitude urban areas that sit on ancient lakes; increasing temperatures plague both; and over-pumping of groundwater has lowered both water tables. In addition, each has a spiraling population. Salt Lake residents, then, should be concerned about the recent news that Mexico City is sinking ("Mexico City, Parched and Sinking, Faces a Water Crisis," New York Times, Feb 18).
Desperate attempts have been made to bring water to Mexico City’s 21 million residents by pumping groundwater. This has depleted this water source and caused the sinking of the city. As pore-filling water is removed, the pores collapse, and the land sinks. Mexico City is now exporting wastewater and importing fresh water to its high-elevation location through canals. But even the canals are failing to flow properly because of the sinking land. The cost of moving water to and from the city is becoming unsustainable
Consider Salt Lake City with its growing population, expected to nearly double by mid-century. We live in a desert and must face the fact that the only water available to us comes from the sky in the form of rain and snow. Precipitation either runs off into the Great Salt Lake (becomes salty and no longer useable), evaporates, or soaks into the ground. The vast majority of our water for domestic, agricultural, industrial use and for watering our lawns is pumped out of the ground. The more we build and pave over the surface of our earth, the greater the runoff and the less soaks in. And with the increasing temperatures and drought conditions in Utah, we have less water coming down to replenish the groundwater.
Let me compare groundwater to an ore body. When the cost of extracting the commodity in the ore body gets higher than the price it can command, the mining town becomes a ghost town. When groundwater is being mined, wells must be drilled deeper to reach it. Someday the cost of extracting groundwater and the collateral costs of importing surface water may exceed what a growing community is willing to pay. Major desert cities will eventually become ghost towns. Is that Salt Lake City’s future?
We have already experienced land sinking in Utah (Utah Geological Survey). If we continue to pump groundwater here, will subsidence become an issue? Additionally, the depletion of our groundwater is affected by our warming Earth, resulting in increased evaporation. The average annual temperature in Utah has continually increased since 1895; the last few years have set records as the warmest, not only in Utah but nationwide.
Utah leaders are already moving water around and considering other major projects in order to bring water to growing cities (Bear River to Salt Lake Valley, Lake Powell pipeline to St. George). The collateral consequences of the Utah projects include drying of the Great Salt Lake, resulting in toxic dust and loss of habitat and depletion of the already overtaxed Colorado River.
For we who choose to live in desert cities, these concerns must be considered for long-term viability. The experience of Mexico City (and other major cities worldwide) should be carefully studied and public policies developed with their consequences kept in mind. Utah and Salt Lake Valley are desirable places to live. But, as with Mexico City, we may damage our environment beyond livability by wanting more than our desert location can supply. Let’s learn from Mexico City. Demand that our local and federal leaders create policy that preserves a healthy and safe community for our families!
L. Cameron Mosher is a geology instructor and author at Salt Lake Community College and member of the Citizens Climate Lobby.