recycling water to save money

San Diego is in a tough spot when it comes to water.  It’s at the far end of the pipeline when it comes to imported supplies from the Colorado River and the California aqueduct, and the Metropolitan Water District (MWD) subsequently charges the San Diego County Water Authority extra for pumping over the extra distance.  It gets less annual rainfall than the LA Basin (10.3 inches in San Diego, 15.1 inches in LA) and has no significant natural rivers (the San Diego River has a flow an order of magnitude lower than the two biggest rivers in the LA Basin, the Los Angeles River and the San Gabriel River), so in some ways it needs imported water even more than Los Angeles.  On top of that, its main wastewater treatment plant, Point Loma, is likely to have its waiver from Secondary Treatment requirements of the Clean Water Act not renewed.  The cost of the required Point Loma upgrades for a 2015 permit could be $1.2 billion.

So a new study for the City of San Diego proposes a way to kill two birds with one stone: recycle treated wastewater into the drinking water supply.  The wastewater discharged to the ocean would decrease, as would the delivery of imported water.  The idea seems to be amenable to the public – a 2011 survey found that two-thirds of the respondents favored adding highly treated recycled water to the drinking water system – and depending on rate increases from MWD, the cost could eventually be lower than imported water.

Water reuse also requires infrastructure, with costs of $2.7 – $3.4 billion over 50 years projected by the report, but the cost savings in required Point Loma upgrades (cost scales with the volumetric flow rate of water treated) could result in a very favorable cost-benefit ratio.  If San Diego pursues this strategy, it could be on the cutting edge of water management in the US.

How not to conduct a public workshop

As I mentioned the other day, there is a lot of frustration and denial on the part of farmers when it comes to nitrate pollution in the Central Valley.  Recently, the UC Davis researchers who wrote the massive report on nitrates in groundwater held a public workshop to formally present their results.  When pressed on the 96% figure for nitrate coming from agricultural sources, one of the scientists acknowledged that the figure may not be “precise”.  Oh dear, you just admitted uncertainty – surely it only went downhill from there.  Where were the error bars in the original study?  If you admit uncertainty, then error bars at least constrain the uncertainty.  An admission of imprecision suggests to the public that it all might be crap.

Turns out that the farmers may have some reasonable issues with the study methodology, partly because the study had to estimate nitrogen fertilizer application rates over the past ~60 years.  Nitrogen prices have gone up significantly, which already presses farmers to be highly efficient in their applications.  Plus there is more and more use of low-water irrigation (e.g., drip irrigation), which further decreases the rate of nitrogen leaching into the groundwater.  The scale of the UC Davis study simply did not permit inclusion of these trends, which suggest that farmers are already mitigating the nitrogen issue as much as they can.  Based on the above article, I doubt that the researchers satisfactorily explained why they conducted the study in the way that they did.

That said, legacy contamination is still an issue, and I don’t think there’s any way that fertilizer application was not the cause of the groundwater nitrate contamination.  So who should pay to clean it up?  I would still argue that nitrogen fertilizers and irrigation water are the easiest things to target, even if it is a burden on the farmers.  The fees would provide a cost-benefit incentive for all farmers to engage low-water irrigation and efficient nitrogen use, plus there is some talk of using contaminated groundwater as irrigation water, letting the nitrates be consumed by crops.  Think that’s unfair, farmers?  Talk to the chemical industry about joint and several liability for Superfund sites under CERCLA…

don’t mind me with my head in the sand

Recently the California State Water Board hired UC Davis to perform a $2 million independent study of groundwater nitrate contamination in the Central Valley, specifically the Tulare Lake Basin and Salinas Valley.  Surprisingly for a government project, the study was completed on time, but not surprisingly the results have already generated some controversy.  UC Davis estimates that 96% of the nitrate in groundwater comes from agricultural  sources, with sources like wastewater treatment plants, septic systems, and manure lagoons minor on the basin scale but potentially significant on a local scale.  Since no one measures basin-wide nitrogen inputs to croplands, the UC Davis researchers had to derive the agricultural data from historical land use per crop, plus a crop-specific nitrogen mass balance.  The approach looks pretty sound to me.

 Two months after the release of data, Tulare County Supervisors are about to strike back.  They voted last week to send a letter of concern to the State Water Resources Control Board, which is coming up with what to do about the nitrate contamination.  The UC Davis report suggests that nitrogen fertilizers should be taxed to cover groundwater remediation for drinking water sources.  This scares the Tulare County agricultural interests, and the Tulare County Supervisors will claim in their letter of concern that the UC Davis report did not consider sources of nitrogen, but rather assumed that the source was agricultural.  Further study is necessary!

I find this very confusing.  In looking at the UC Davis approach, they did consider the source of nitrogen contamination, and in fact Figure 1 of the Executive Summary shows their breakdown of the nitrogen sources.  So what gives?  I think this is a last-ditch effort of agricultural interests to resist the reality of numbers staring them in the face.  After all, these are some of the most productive agricultural lands in the world (including 10% of US milk production), so anything that might decrease productivity is a threat.  But the number of drinking water wells with elevated nitrate in these basins is only increasing with time, and for agriculture to refuse to acknowledge complicity in the problem is to live with their heads in the sand.

Loopholes and Desert Springs

Making the rounds in the California news these days is a ploy by the owners of water rights in the Mojave Desert near Cadiz, to mine groundwater and sell it to utilities in southern California.  Currently, rainfall in the basin enters the groundwater table, traveling slowly underground to two dry salt lakebeds, where the water resurfaces and evaporates away.  The business group Cadiz, Inc. thinks that this is a waste of perfectly good water resources, and wants to extract the water just upstream of the lakes, deliver it just 50 miles to the Colorado River Aqueduct (map here), then make lots of money from the water sale.

There are a couple of problems with this approach.  First, the groundwater in question supplies natural springs in the Mojave Natural Preserve, and the actual impact of pumping on the springs is likely to be different than the “no impact” that the businessmen assume.  Secondly, the exraction plan is completely unsustainable.  The Cadiz group has estimated the annual recharge of the basin for the past 50 years, and assumes that this will continue for the coming 100 years.  They then intend to extract 100 years’ worth of recharge in just 50 years.  The second 50 years will allow the basin to rebound from the intensive extraction.  Third, even with such an odd plan, independent scientists suggest that the actual natural recharge rate is 10-50% of the rate that Cadiz assumes, meaning that it will take many centuries for the basin to recover.

I saw the Cadiz scientists present their data monitoring plan in Sacramento a couple of weeks ago at a Groundwater Resources Association of California legislative symposium.  It was a terrible presentation, in my opinion — lots of figures with tiny writing and too many slides, so that we never got the full message of each slide.  It felt like they were trying to sell us on something bogus.  There were many questions from the professionals in the room, ranging from the impact of extraction on local rainfall to the potential of the dry lakebeds to turn into environmental hazards in the way that Owens Lake has. (Owens Lake’s inflow was diverted to the Los Angeles Aqueduct nearly 100 years ago, but the dry lake sediments that have been exposed are a huge dust and air pollution problem, and LA has been forced to cut back on its diversions to keep the sediments wet.)  Theoretically this would be addressed in the Environmental Impact Report, but Cadiz is trying to get away with the minimum impact assessment because they’re on former railroad territory, which gets an exemption from much of the state and federal environmental legislation.

The issue that they didn’t cover that day, and haven’t covered in any subsequent press, is why on earth they would devise such an intense extraction plan.  If they were to withdraw groundwater at roughly the recharge rate, they could deliver water indefinitely, which would be years upon years of profit.  Instead, they are focused on a 50-year time window for their sales.  Maybe it would require that much in water sales to make the rest of the capital costs for the 50-mile pipeline come out in the black.  But to me, it all reeks of short-term profit-seeking.  What will the southern Californian water utilities do when the 50-year extraction is over?  They’ll have just delayed the inevitable, and let more people get used to unsustainable water resources.  It just sounds like a bad idea.

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.