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Bridging climate science, citizens, and policy


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Water efficiency

I saw a tweet last night that I found interesting.

“The only thing that can.”  I hope Peter means water-use efficiency for all users.  The graphic he includes with this tweet suggests he’s focused on household toilet usage in California.  I’ll round the numbers used in the graphic: 1980 usage was 800,000 acre-feet per year; current use (no efficiency) is 1,200,000 acre-feet per year.  Current savings from efficiency improvements: 640,000 acre-feet per year.  Additional potential savings: 290,000 acre-feet per year.

The 640,000 AFY is laudable.  That’s a lot of water that Californians don’t have to use and thankfully aren’t.  That is a real accomplishment.  An additional 290,000 AFY is a good goal to work on – why waste a resource when you don’t have to.

But toilet water usage isn’t the primary usage of California water – and it’s that small point that troubled me when I saw the tweet.  Total water usage in California is 40,00,000 AFY.  That 640,000 efficiency represents just 1.6% of the total usage.  It also represents >50% reduction from what water usage could be without any efficiency measures.  What I want to know is what efficiencies water-thirsty California agriculture implements.  Agriculture is by far the dominant user of water – if we achieved just 1% sector efficiency, how much more water could California save because of the scale of industry usage compared to residential usage?

Agriculture is a sizable part of the California economy – $43 billion industry that generates $100 billion in overall economic activity.  Because of that, agriculture wields political clout in Sacramento.  This means that while physical scientists can inform policymakers on the ongoing drought, we need the social sciences to inform policymakers how to deal with it.  I would also like to see quantitative results of efficiency gains by sector.