A resource is said to be at “peak,” when it becomes so inaccessible that the extraction rate starts to decline. The Pacific Institute has published a paper, “Peak Water Limits to Freshwater Withdrawal and Use,” (.pdf; 32KB) finding that “peak water” was reached sometime around 1970 in the United States.
The paper’s authors, Peter Gleick and Meena Palaniappan, identify three classes of peak water:
- Peak renewable water: Where flow constraints limit total water availability over time. River basins and snow melt are the most common examples. No water from the Colorado River, for example, has reached the ocean since about 1960.
- Peak nonrenewable water: Where production rates substantially exceed natural recharge rates or where overpumping or contamination leads to a peak production followed by a decline (similar to peak oil curves). An example of nonrenewable water are aquifers. Aquifers in the US, China, and India are all being drained at a rate much faster than can be recharged. As these aquifers are depleted, use will drop to the recharge rate.
- Peak ecological water: The point beyond which the total costs of ecological disruptions and damages exceed the total value provided by human use of that water. Examples of ecological water are lakes and rivers.
While we’re not running out of water—use of which in the US paralleled gross domestic product (GDP) growth since the beginning of the 20th century until 1975 when it stabilized—we have reached the end of cheap and easy access to the resource.
The obvious, sustainable solution is to make more currently inaccessible water available by changing our dumping habits and cleaning up existing watersheds. But this is what’s called a “backstop” solution and, as Gleick and Palaniappan note, “the ultimate water backstop is still water.”
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