The purpose of my note was not to suggest ways to reduce CO2 emissions. It was to counter the assertion that desalination is impractical because it necessarily increases them. The scope of this discussion was limited to addressing that assertion, not to list ways to reduce CO2 emissions in general.
Rainwater collection is not a substitute for desalination because in many years there is little or no rain. The author's principal position is that there is no drought because once every 10 or 20 years there is (or was) a wet one; of course, to conclude this he includes the extremely wet 2004 and excludes the extremely dry 2013-2015. Even if we ignore his cherry-picking, that position is not a sensible one; it is equivalent to asserting that with an infinitely large reservoir, California would always have enough water regardless of the consumption rate. The reality is that consumption exceeds the long-term average supply by a considerable margin and has increased due to population growth even as the likely future supply is shrinking. Furthermore, large quantities of water cannot be stored forever; it evaporates, seeps into the ground, or both. The wet years, rare even in the past and likely to be moreso in the future, don't come often enough to keep reservoirs full. There's also the problem of the inland cities, where even historical average rainfall is far below 14 inches a year, which the author conveniently ignores.
Rainwater collection and recycling of treated sewage are therefore necessary but insufficient measures (at least in southern and inland California; they're probably sufficient for places like Eureka). In addition to those measures, additional sources will have to be found and/or large-scale reductions in consumption will be required. Desalination is perhaps the only plausible means of increasing supply (all Western river systems are already critically oversubscribed), and while it is costly, it does come without the political problems of forcibly reducing consumption. As such, I predict that solar-powered desalination will eventually become the central piece of the state's response to its water shortage. It does a good job of matching plentiful resources (solar energy, ocean water) to visible needs (more water for coastal cities). It does not address the needs of agriculture, but nothing can. The only policy options with respect to agriculture are in assigning the required curtailments. For political reasons, they'll probably also build more storage, but the practical benefits of that storage to agricultural users will be minimal as it will be empty or dead pool most of the time.
These aren't things anyone wants to hear, but they're reality. The author, like many others, is whistling past the graveyard. Anyone who believes that simple, inexpensive measures can address the problem is in denial of its true scope and scale.
I respect your opinion, but let me reiterate my two main points:
1. Storing rainwater (underground, with very little evaporation) is much more energy efficient than desalination. Could this alone fix all the problems of water supply even just for cities? Maybe not, but what it can do, it can do very efficiently. Even if it's not at all cheap and easy: I didn't run the numbers, but I'm pretty sure that building that kind of distributed storage capacity is much more expensive upfront than building an "equivalent" desalination plant. The difference is that the desalination plant will burn energy forever, while the water storage will use much, much, much less. Even if the historical average were say half the 14 inches quoted in the article, you would "just" need to cover a bigger catchment area.
2. We don't have infinite resources, and we can only build so much electrical power capacity from solar every year. As long as most of the electrical power generation emits CO2 (and worse), the more electrical power you use for desalination, the more CO2 you're going to emit.
Rainwater collection is not a substitute for desalination because in many years there is little or no rain. The author's principal position is that there is no drought because once every 10 or 20 years there is (or was) a wet one; of course, to conclude this he includes the extremely wet 2004 and excludes the extremely dry 2013-2015. Even if we ignore his cherry-picking, that position is not a sensible one; it is equivalent to asserting that with an infinitely large reservoir, California would always have enough water regardless of the consumption rate. The reality is that consumption exceeds the long-term average supply by a considerable margin and has increased due to population growth even as the likely future supply is shrinking. Furthermore, large quantities of water cannot be stored forever; it evaporates, seeps into the ground, or both. The wet years, rare even in the past and likely to be moreso in the future, don't come often enough to keep reservoirs full. There's also the problem of the inland cities, where even historical average rainfall is far below 14 inches a year, which the author conveniently ignores.
Rainwater collection and recycling of treated sewage are therefore necessary but insufficient measures (at least in southern and inland California; they're probably sufficient for places like Eureka). In addition to those measures, additional sources will have to be found and/or large-scale reductions in consumption will be required. Desalination is perhaps the only plausible means of increasing supply (all Western river systems are already critically oversubscribed), and while it is costly, it does come without the political problems of forcibly reducing consumption. As such, I predict that solar-powered desalination will eventually become the central piece of the state's response to its water shortage. It does a good job of matching plentiful resources (solar energy, ocean water) to visible needs (more water for coastal cities). It does not address the needs of agriculture, but nothing can. The only policy options with respect to agriculture are in assigning the required curtailments. For political reasons, they'll probably also build more storage, but the practical benefits of that storage to agricultural users will be minimal as it will be empty or dead pool most of the time.
These aren't things anyone wants to hear, but they're reality. The author, like many others, is whistling past the graveyard. Anyone who believes that simple, inexpensive measures can address the problem is in denial of its true scope and scale.