We want solar now!

Apparently some picture of Indians using a photovoltaic (PV) panel above a water canal has gotten some Californians clamoring for PV all over California’s major aqueducts.  Someone ran a rough look at the numbers here.  It is true that harnessing solar energy would offset the energy footprint of moving all that water around, which is not trivial.  But there are a couple of reasons why any water manager should be skeptical of this option, which aren’t widely publicized.

  1. California’s aqueducts, open to the atmosphere, receive a high dose of natural UV irradiation as the water travels, which acts as a natural disinfectant to keep down microbial growth.  This means that the water quality would decrease if the UV rays were captured for energy purposes.  Drinking water utilities would likely need to spend more money (and energy) on water treatment to offset this natural treatment process. (As an aside, this is what concerns me about Christo’s art project in which he wants to drape fabric over six miles of the Arkansas River in Colorado.)
  2. PV panels get dirty, especially in the desert.  You know what they use to clean PV?  Water.  So you’d also lose some of the water to cleaning those hundreds of miles of panels, which at scale is also not trivial.
  3. Finally, there is the cost of PV itself.  Solar projects are notoriously capital intensive, which is one reason that they have a tough time competing with non-renewable energy projects like coal and natural gas, which have higher operations and maintenance costs.  The installation above the aqueduct channels would require new design and likely extra steel to straddle the wide channels, compared to normal solar arrays mounted on single posts.

My guess is, utilities like Metropolitan Water District of Southern California, which owns the Colorado River aqueduct, or the Los Angeles Department of Water and Power, which owns the Los Angeles aqueduct, have done enough cost analysis to determine that the benefits do not outweigh the costs (and the financial risks) in this case.  It’s understandable to me that they would be very conservative when it comes to anything that might disrupt their most valuable resource: water.

wasteful outdoor water use

When you look at the water balance for a municipality, at how much water is treated to high-quality drinking water standards vs. how much actually ends up in our wastewater treatment system, there is a striking imbalance.  Of the treated drinking water in the Los Angeles basin, for example, my numbers suggest that maybe 50-60% makes it to a wastewater treatment facility.  Assuming minimal use of off-grid septic systems, where is the other 40-50% going?

The short answer is outdoor water use.  Grass and non-native plants require a lot of water to stay healthy, and in our “I have a right to cheap water” mindsets, the water for our plants and cars is not a big deal.  Cinnamon McIntosh, a water conservation specialist for Casitas Municipal Water District in Southern California, recently stated that typical overwatered lawns in Southern California receive twice the amount of water as there is rainfall in Ireland.  Granted, there’s a lot more evaporation in SoCal than in Ireland, but surely we can do better than this.

Add water scarcity to the equation, and you can understand why water agencies have an interest in water conservation among the people they serve.  From paying customers to switch to native plants and grasses to implementing outdoor watering restrictions to price increases, various methods are being tried.  Los Angeles has been fairly successful in these techniques, and its per capita water use of 123 gallons per day is the lowest in any US city with a population over 1 million.  That said, the LA Department of Water and Power has noticed an uptick in water use this dry winter, especially among single-family homes…which likely points to outdoor water use.

I hesitate to say we should go so far as to jail those who water lawns or wash cars outdoors, but sometimes threat of penalty (the proverbial “stick”) reaches people’s minds more readily than this situation’s proverbial “carrot”: more efficient water use.