A sometimes poorly understood piece of the water story is the question of scale – the truly enormous quantities of water required to do human stuff like be a city or grow our food.
This is the shortcoming of well-meaning suggestions like building a pipeline to the Missouri River or a string of desalination plants along the coast, or a string of desal plants that connect up with big pipelines criss-crossing the country.
Writing in the San Jose Mercury-News last week, Stanford’s Leon Szeptycki and Newsha Ajami gave a nice explanation of the problem in the context of California’s ever-present desal discussion:
We withdraw approximately 42 million acre-feet per year from rivers, streams, and aquifers in California. We use up a net total of 33 million acre-feet of that. According to the 2013 update to the state’s water plan, even if every proposed ocean desalination facility were built (an unlikely scenario), they would produce a combined total of approximately 382 thousand acre-feet a year, less than 1 percent of the state’s existing water budget.
This doesn’t mean that desal does not have a place at the margins, in niches where there is no good alternative. But in general the scale of our water use is far too vast to have any impact on the overall problem.