Comments on the alleged megadrought

During the past few weeks, media have been hyping alarm about a new study  that claims that the Southwestern US is entering a megadrought and that the drought is made more severe by human-caused global warming. That claim is based on tree-ring analysis and computer modeling speculation.

Droughts have occurred due to natural cycles, but there is no physical evidence that carbon dioxide emissions play a significant role is controlling global temperature or precipitation. The new paper presents no evidence that alleged “human-caused” global warming is making the drought worse, it is just speculation. In fact, many droughts are associated with cooler periods.

Let’s put things in perspective. Here are the data for the past 1,200 years. It seems that “megadroughts” have occurred naturally, without any human influence.

These data show that the 20th century was wetter than normal. However, the next graph shows that there have been droughts. But, rather that entering a megadrought, we seem to be emerging from a dryer period according to NOAA.

The graph above comes from a 4-minute video posted by Tony Heller, on his “Real Climate Science” blog. This video destroys claims that the western United States is currently experiencing a nearly unprecedented megadrought. Video: https://youtu.be/W9xCWDZmUT4



Evidence that CO2 emissions do not intensify the greenhouse effect

The Broken Greenhouse – Why CO2 is a minor player in global climate

A Review of the state of Climate Science

Drought in the West

Desalination of Sea Water Can Augment Our Water Supply Without Harming Sea Life

Since the Colorado River may not supply us with all the water we need, we should turn to the oceans.

Desalination of sea water can produce the freshwater we need to augment our natural supplies. The most common method is reverse osmosis where the sea water is forced through a semi-permeable membrane which removes the salt.

However, the process is energy intensive which some environmentalists claim will put more dread carbon dioxide into the atmosphere if the electricity comes from fossil-fuels. That can be solved by powering the plants with small, dedicated nuclear generators. (Powering such plants with wind or solar energy will make freshwater production intermittent and unpredictable.)

The other claim by some environmentalists is that the effluent from the desalinization process, very salty brine, is harmful to wildlife. A new study shows this concern is overblown.

A seven-year study, jointly conducted by Southern Cross University and the University of New South Wales at the Sydney (Australia) desalination plant found that when the plant was in operation, fish population in the area almost tripled. Fish populations decreased to normal when the plant was not operating. The Sydney plant has a capacity of producing 74,000 acre-feet of water per year.

Lead researcher Professor Brendan Kelaher said, “At the start of this project, we thought the hypersaline brine would negatively impact fish life. We were surprised and impressed at the clear positive effect on the abundance of fish, as well as the numbers of fish species. Importantly, the positive effects on fish life also included a 133 per cent increase in fish targeted by commercial and recreational fishers. As to why fish like it so much, we think they might be responding to turbulence created by dynamic mixing associated with the high-pressure release of the brine. However, more research is needed.” (Source) The report mentions no detrimental effects on fish or other sea life. The research was published in the journal Environmental Science & Technology. http://pubs.acs.org/doi/abs/10.1021/acs.est.9b03565

I did try to find information on negative impacts to marine life of concentrated brine being pumped into the ocean, but all I could find was speculation, no actual physical evidence. Apparently harm is minimal. As noted by marine biologist Daniel Cartamil of Scripps Institution of Oceanography, intake water may contain tiny organisms (plankton), including the eggs and larvae of marine life. None of these organisms survive their journey through the plant. However, this entrainment typically accounts for only about 1 percent or 2 percent of plankton mortality in a given area. Cartamil says this about the salty brine discharge: “In theory, marine life (particularly plankton) could be harmed by prolonged exposure to salinity levels higher than those they normally cope with. The most common solution to this problem is to mix the brine back into the seawater with high-speed jets, a process so efficient that salinity levels are effectively back to normal within 100 feet of the release point.” (Source)

Perhaps Arizona, California, and Mexico will take heart and build more modern desalination plants near the Sea of Cortez and the Pacific Ocean to help ease our dependence on the Colorado River. Some of the salt could be recovered for industrial applications. There is a desalination plant in Yuma, built in 1992 to treat agricultural runoff and conserve water in Lake Mead. But its technology is outdated. There is also a desalination plant just north of San Diego with a capacity of 56,000 acre-feet per year. Building more and bigger desalination plants powered by nuclear generators is technologically feasible but politically problematic.

Articles on small nuclear reactors:

A New Type of Molten Salt Nuclear Reactor

Small Modular Reactor by Westinghouse

What are small modular nuclear reactors, and why are three provinces uniting to build them?

Advanced Small Modular Reactors

Forest thinning needed to save water

Dense forests suck up surface and groundwater and dump it into the atmosphere through the process of evapotranspiration. This means that there is less water for other uses.

“There are too many trees in Sierra Nevada forests, say scientists affiliated with the National Science Foundation (NSF) Southern Sierra Critical Zone Observatory (CZO).”

A new study supported by the National Science Foundation published in the journal Ecohydrology (see press release) proclaims “Billions of gallons of water saved by thinning forests.” The study of the Sierra Nevada Mountains in California notes that “excessive evapotranspiration may harm a fragile California water system, especially during prolonged, warm droughts.”

The primary methods of good forest thinning are fire and logging.

Forest Service policy exacerbated sound forest management. Remember Smokey the Bear, “only you can prevent forest fires?” But fire is nature’s way of managing forests. Logging was largely reduced for misguided environmental reasons such as saving the spotted owl.

From the NSF study:

“Forest wildfires are often considered disasters,” said Richard Yuretich, director of NSF’s CZO program, which funded the research. “But fire is part of healthy forest ecosystems. By thinning out trees, fires can reduce water stress in forests and ease water shortages during droughts. And by reducing the water used by plants, more rainfall flows into rivers and accumulates in groundwater.”

Using data from CZO measurement towers and U.S. Geological Survey satellites, researchers found that over the period 1990 to 2008, fire-thinned forests saved 3.7 billion gallons of water annually in California’s Kings River Basin and …17 billion gallons of water annually in the American River Basin — water that would otherwise have been lost through evapotranspiration.

Forest thinning has increased in recent decades in an effort to stave off disastrous wildfires fueled by dense forests. This study shows that restoring forests through mechanical thinning or wildfire can also save California billions of gallons of water each year.

Perhaps we should take guidance from the first land managers in North America, the Indians. In my article “The Pristine Myth” I note the following:

Archaeological and anthropological research during the last 25 years or so, shows that much of what we thought was pristine in the Western Hemisphere, even the Amazon rain forest, is actually human-formed landscape created by the first New World inhabitants, the Indians. It seems that American Indians, from North America, Mexico and South America, were the ultimate land managers, and they transformed the land to suit their needs. They constructed the world’s largest gardens.

American Indians built cities and civilizations, cultivated forests and farms, and developed more than half of the crops grown worldwide today. Indians, rather than subsist passively on what wild nature provided, instead survived by cleverly exploiting their environment. Their principal tool was fire. They did not domesticate animals for meat, but instead used fire to change whole ecosystems to raise deer, elk, and bison.

Related story:

Forest thinning may increase runoff and supplement our water supply

A new study (“Effects of Climate Variability and Accelerated Forest Thinning on Watershed-Scale Runoff in Southwestern USA Ponderosa Pine Forests” published October 22, 2014) conducted by The Nature Conservancy and Northern Arizona University recommends accelerated forest thinning by mechanical means and controlled burns in central and northern Arizona forests. The study estimates that such thinning will increase runoff by about 20 percent, add to our water supply, and make forests more resilient.

American Geosciences Institute’s Critical Issues program


The Arizona Geological Survey’s winter e-magazine features an article about the American Geosciences Institute’s Critical Issues program (www.americangeosciences.org/critical-issues).

The aim of this AGI program is to pioneer a new approach to sharing societally-relevant science with state and local decision makers. “Here in Arizona, we are sharing this with state and local decision-makers to help them wrap their heads around the complex issues involving groundwater, geologic hazards, and sustainable natural resource management.”

The program aims to support connections and communication between the geoscience community and decision makers. Although the program caters to decision makers at all levels, it particularly focuses on state and local decision makers because these stakeholders are commonly underserved by geoscience policy efforts.

The program convenes meetings, such as the AGI Critical Issues Forum, but its main interface is a web-based platform of resources that bring the expertise of the geoscience community to decision makers by offering a curated selection of information products from sources that include state geological surveys, federal and state agencies, and AGI’s member societies.

The Critical Issues program offers the following freely accessible information services:

Research database: Over 4,000 publications primarily from state geological surveys and the U.S. Geological Survey.

Webinars: Free webinars on a variety of topics that bring geoscientists and decision makers together to discuss potential solutions to challenges at the interface of geoscience and society.

Maps & Visualizations: 144 interactive maps and visualizations covering all 50 states and the District of Columbia.

Case studies: A new product that is coming online in Spring 2017. Specific applications of geoscience to societal problems.

Fact Sheets: A new product that is coming online in Spring 2017. Provide more in-depth information on the big issues.

Frequently Asked Questions: 105 questions on topics including: climate, energy, hazards, mineral resources, and water.

Read more at:


This AZGS e-Magazine also includes an article about groundwater use in the United States.


Implications of projected climate change for groundwater recharge in the western United States – paper review

A group of 17 researchers, led by Thomas Meixner of the University of Arizona, attempted to assess the possible response of groundwater recharge to global warming in eight basins in the western U.S. In this context, “recharge” means the replenishment of water in aquifers from some surface source.

Meixner recharge fig 1

The paper: Meixner et al, 2016, Implications of projected climate change for groundwater recharge in the western United States, Journal of Hydrology, Volume 534, March 2016, Pages 124–138.

You can download the full PDF.

The authors assume future climate conditions will be as projected in the most recent National Climate Data Assessment (2014) which itself is very speculative and lacks any supporting physical evidence (see links to my articles below).

The authors acknowledge that their study comes with a great deal of uncertainty. That did not stop Tony Davis from asserting in the Arizona Daily Star that “groundwater recharge in the San Pedro will decline faster than in any of seven other Western groundwater basins…” Tony apparently did not read the part about the Central Valley of California nor the part about the San Pedro in the paper itself.

Here is an excerpt from the paper’s abstract:

“Eight representative aquifers located across the region were evaluated. For each aquifer published recharge budget components were converted into four standard recharge mechanisms: diffuse, focused, irrigation, and mountain-systems recharge. Future changes in individual recharge mechanisms and total recharge were then estimated for each aquifer. Model-based studies of projected climate-change effects on recharge were available and utilized for half of the aquifers. For the remainder, forecasted changes in temperature and precipitation were logically propagated through each recharge mechanism producing qualitative estimates of direction of changes in recharge only (not magnitude).”

“Several key patterns emerge from the analysis. First, the available estimates indicate average declines of 10–20% in total recharge across the southern aquifers, but with a wide range of uncertainty that includes no change. Second, the northern set of aquifers will likely incur little change to slight increases in total recharge. Third, mountain system recharge is expected to decline across much of the region due to decreased snowpack, with that impact lessening with higher elevation and latitude.”

“Factors contributing the greatest uncertainty in the estimates include: (1) limited studies quantitatively coupling climate projections to recharge estimation methods using detailed, process-based numerical models; (2) a generally poor understanding of hydrologic flow paths and processes in mountain systems; (3) difficulty predicting the response of focused recharge to potential changes in the frequency and intensity of extreme precipitation events; and (4) unconstrained feedbacks between climate, irrigation practices, and recharge in highly developed aquifer systems.”

In other words, this paper is long on speculation and short on physical data.

Meixner mapHere is what they predict for each of the eight basins due to global warming:

High Plains Aquifer (aka Ogallala aquifer):

The paper projects moderate increases in recharge in the north and shifting to moderate decreases in the south or an overall net decrease in recharge depending on which data set is used.

San Pedro River:

The authors relied on two other studies which project a 30% and a 27% decrease in recharge over the next 100 years. However, the authors also note that depending which climate model was used, “Future recharge varied from a 100% decline in recharge to a 30% increase in recharge across the GCMs used.” That large range of uncertainty detracts from the value of the study.

Death Valley:

The paper predicts less recharge due to decreased snowpack in the surrounding mountains. That project is hedged: “Sources of uncertainty include potential increases in summer precipitation and winter precipitation intensity, which could lead to increased focused recharge. This source of recharge is currently so small that even large relative changes would result in negligible changes to total recharge.”

Wasatch Front Aquifers:

The paper predicts a general decrease in recharge (unless there is more snowpack).

Central Valley Aquifer:

Here, recharge is dominated by irrigation. Modeling projects decreases on anywhere between 5% and 60%.

Columbia Plateau:

There might be a modest increase in recharge if it rains more.

Spokane Valley-Rathdrum Prairie aquifer:

The authors don’t know because of the great uncertainty of the data.

Williston Basin aquifer system:

Some “considerations suggest that diffuse recharge to the Williston Basin may decline. However, model-based projections in multiple studies of future recharge to the northern HPA [high plains aquifer], located directly south of the Williston Basin, indicate that diffuse recharge will increase. Given these inconsistent outlooks, uncertainty in future diffuse recharge is high.” In other words, the authors don’t know about that one either.

The goal of this study was to provide information that would help planners form water policy for the future. Considering the high level of uncertainty, do you think this study will help?

Study funding: This study receive support from the U. S. Geological Survey and the National Science Foundation through a concurrent award (EAR-1328505). Additional support to several authors was provided by the USGS National Research Program and the USGS Office of Groundwater.”

Your tax dollars at work.


See also:

National Climate Assessment lacks facts, an analysis

National Climate Assessment = science fiction and politics

San Pedro River Geology – Implications for water law

How Tucson Water spends Conservation Fund money and a suggestion for a better way

If you are a Tucson Water customer, you may have noticed an item on the back page of your water bill listed as: “CONSRV FEE $.07/CCF.” This means you are contributing seven cents per cubic foot of water used to a conservation fund. That may not sound like much, but according to an article by Tim Steller, that added up to $2.95 million last year. By the way, this “contribution” to the conservation fund will rise to eight cents per CCF on July 15.

So, how is that money being used? The answer to that question is the objective of a Freedom of Information (FOIA) request filed last January by Mark Lewis, one of five members of the City’s Conservation and Education Subcommittee of the Citizens Water Advisory Committee.

Tucson Water has to date refused to provide the information requested by Mr. Lewis. According to Mr. Lewis, the information requested is “to gather the documentation and information necessary to ensure the funds collected from Tucson Water customers under the Conservation Fee program has been properly accounted for, audited, and expensed.” Mr. Lewis has expressed concern, in his role as an appointed advocate for the Rate Payers of Tucson Water, that the millions of dollars which have been spent through this fund have not been properly tracked or audited and that more recent uses of this fund are not consistent with the purpose of the fund: conserving water.

One conservation program promoted by Tucson Water is the replacement of old toilets with new low-flow models. Tucson Water will give you a $75 rebate toward the cost. According to Steller’s article, “water-wasting toilets remain in around 150,000 Tucson homes, and the program to replace them saved almost 11 million gallons in the first eight months of this fiscal year alone.” Mr. Lewis supports this program, but points out that the small rebate may be insufficient, especially for older homes which may have complicated plumbing issues that would make replacement more expensive.

Another conservation program is rainwater harvesting. Tucson Water will provide a rebate of up to $2000 for installing a system. Steller points out that “those rebates have mostly benefitted wealthier residents and so far have resulted in no measurable reduction in water use.” Mr. Lewis notes that the $900,000 in rain water rebates to date saved no water, but had the same money been spent on wasteful toilets it would have saved 173 million gallons of water to date.

You can read about the program in a brochure provided by Tucson Water: http://www.tucsonaz.gov/files/water/docs/Rainwater_Harvesting_Rebate_brochure.pdf

In that brochure, Tucson Water claims that “45% of the water we use goes to outdoor irrigation.” That number surprises me; I wonder if it is true. The brochure also notes that in order to qualify for the rebate, you have to take a free class. And here is where it gets interesting.

The qualifying class is run by Watershed Management Group, a consulting firm that, for a fee, will design a rainwater harvesting system for you. Three board members of Watershed Management Group, Catlow Shipek, Mark Murphy, and Amy McCoy, comprise three of the five members of the City’s Conservation and Education Subcommittee of the Citizens Water Advisory Committee. The classes are also given by a company that sells rain gutters according to Mr. Lewis. This situation has the appearance of crony capitalism and conflict of interest.

There is another scheme afoot. Tucson City Councilwoman Regina Romero has proposed that $300,000 be used to provide interest free loans to low-income residents so they can plant trees and have them watered by rainwater harvesting systems. Romero is concerned about the “unequal distribution of tree canopy in Tucson…” and its effect on the Urban Heat Island Effect (cities are warmer than surrounding countryside because all the asphalt and concrete absorb heat which makes nighttime cooling much slower). I see two potential problems with this scheme. First, we would have to cover a large part of the city with trees to have any significant effect. Second, all those trees will transpire water, losing moisture to the atmosphere rather than conserving water for reuse.

Given the information above, do you think your forced subsidy is being well-spent?

I have a suggestion on how the money could be spent to actually conserve water.

One of the eco-fads promoted by Tucson Water is rainwater harvesting at residences. So far, that program has resulted in no measurable reduction in water use. But perhaps, if that idea was used on a larger scale, it could help recharge our aquifers. Why don’t we collect storm-water runoff from city streets and in ephemeral flows in the Santa Cruz River and pump that water back into the aquifers via dry wells?

That idea is discussed by Chuck Graf, Senior Hydrologist, Arizona Department of

Environmental Quality in a short article in the Spring Issue of Arizona Water Resource Newsletter (link to article).

This idea is not new. Phoenix began recharging storm-water in the 1930s and now has more than 50,000 wells in operation. Many other communities also use this recharge method. Why not in Tucson and Pima County?

The practice of dry well recharge in Phoenix went largely unregulated until 1987 when legislature directed the Arizona Department of Environmental Quality (ADEQ) to license dry well installers and establish a registration program for existing and newly constructed dry wells. The law expressly limited the use of dry wells to the disposal of storm water. This limitation was intended to prevent disposal of hazardous chemicals into dry wells, which in the past had caused severe groundwater contamination plumes (some of which are still under remediation).

Graf explains the dry well method as follows:

“The dry well borehole is drilled in alluvial sediments, through any intervening fine-grained and cemented zones, into a permeable layer of clay-free sand, gravel, and cobbles. The permeable layer serves as the injection zone for the storm water. ADEQ requires at least 10 feet of separation between the bottom of the injection zone and the water table. Because groundwater commonly occurs at great depth in Arizona’s alluvial basins, installers often have considerable leeway to find an exceptionally permeable zone above the water table that maximizes dry well performance while maintaining a much greater separation distance than the 10-foot minimum.”

Graf goes on to write:

“Potential adverse groundwater quality impact is the biggest concern about dry wells. Although the definitive water quality study probably remains to be done, a number of studies, including a 10-year study in Los Angeles conducted by the Bureau of Reclamation and others, found little evidence for groundwater contamination. A 1985 study in Phoenix found that dry wells had a beneficial effect on groundwater quality with respect to major chemical constituents”

This idea should be considered. Perhaps then, our involuntary contribution to the “Conservation Fund” would actually conserve some water.


The Redwall Limestone of the Grand Canyon


Redwall 2

The 350-million year old Redwall Limestone is one of the most prominent features of the Grand Canyon. Its features:

• Diverse and long history over the last 350 million years.
• Magnificent cliffs and red walls.
• Composed of ~99.5% pure limestone, ~95% of which is biologically formed in the presence of organisms.
• Forms very chemically resistant cliffs, yet it is a very soft rock (slightly harder than a
finger nail).
• Has 1,000’s of miles of interconnected caverns spread out over the Colorado Plateau.
• Has many caverns, some with ancient and modern speleothems.
• Is the source of carbonate for the growth of abundant travertine deposits.
• Provides precious minerals, trace metals and uranium in breccia pipes
• Is a major source of high quality groundwater to numerous and voluminous springs in
the canyon and region, consumed by most visitors to the canyon.
• “Living in the Past” implies the past of the Redwall Limestone is living with us today.

Brian Gootee of the Arizona Geological Survey has designed a 27-slide history of the Redwall Limestone intended for guides and educators. It can be downloaded here:

It has great graphics and an interesting story.

See also:

Origin of the Grand Canyon
Origin of the Lower Colorado River – a geological detective story



Rosemont’s Conservation Lands Program

In addition to mine development, Rosemont Copper has a land conservation program which currently includes five sites in southern Arizona, see map below. Rosemont says the program will “permanently conserve 4,500 acres of open space, and allocate more than 550 million gallons per year of private surface water rights to the public.”


The following short descriptions are taken from Rosemont’s brochure on the program.  For that brochure and more details on each  property go to: http://rosemontcopper.com/conservation.html .

1. Fullerton Ranch:

Adjacent to existing county conservation land, acquisition of this property maintains open land for hiking, bird watching, hunting, camping, mountain biking and off-roading. While over-grazed today, sustainable grazing to support local ranching can be supported on the property. The property provides a valuable habitat for the Desert Box Tortoise and other species. Without conservation, the property would be subject to fragmentation and development.

2. Helvetia Ranch North:

The Helvetia Ranch North property connects BLM Santa Rita Experimental Range land to the Coronado National Forest. Its conservation ensures an intact cultural and natural landscape, completes wildlife corridor connections, and maintains public access to the Santa Rita Mountains. The Ranch also provides habitat for vulnerable and endangered species like the Pima Pineapple Cactus, the Mexican Long-Tongued Bat, and the Lesser Long-Nosed Bat.

3. Sonoita Creek Ranch:

Located at the headwaters of the Patagonia-Sonoita Creek Preserve, the Sonoita Creek Ranch property plays an essential role in the recharging of the Town of Patagonia’s aquifer. Prior to its purchase by Rosemont, Sonoita Creek was poised for residential development. Now Sonoita Creek Ranch and its 588 acre-feet per year surface water right, fed by a perennial spring, will be conserved.

4. Pantano Dam:

Rosemont, working with the state and local agencies, hopes to be successful negotiating projects that will use existing private water rights for the enhancement of an important stream habitat in the Pantano Wash, Davidson Canyon, Lower and Upper Cienega Creek and Empire Gulch. These enhancement projects, both downstream and upstream, would create a habitat for endangered species with a priority water right that Rosemont has secured.

5. Davidson Canyon Ranches:

Each of these is a historic homestead, chosen by the homesteader because of a flowing spring. Conservation of these sites ensures the lands will be kept open rather than developed, preserving public views, numerous archeological sites, and the reach of the seasonal Davidson Canyon Wash that a downstream of which has been designated as an Outstanding Arizona Water.

See also:

The value of mining in Arizona

Distinguishing Fact from Fiction about Rosemont

Future of Rosemont Mine Very Certain

Rosemont answers Cyanide Beach

Pima County versus Rosemont

Rosemont’s dry-stacked tailings will be greener than those near Green Valley

Jaguars versus the Rosemont mine

Tucson’s Water Action Plan, Fuzzy Sustainable Development

The City of Tucson and Pima County are collaborating on a region water plan. It’s about time. But you should read the reports: government concepts of priorities might not be the same as those held by property owners and businesses.

Over the past several years, local governments have been devising a plan to maintain and ensure water supply for the future. A “Phase 1” report deals with an inventory of water resources and an assessment of infrastructure. A “Phase 2” report “establishes a framework for sustainable water resources planning including 19 goals and 56 recommendations within four interconnected elements: Water Supply, Demand Management, Comprehensive Integrated Planning, and Respect for Environment.”

The new Action Plan describes a range of activities with time lines to implement the goals and

recommendations in the Phase 2 Report. The City wants your comments.

From my reading of the plan, the City is placing great emphasis on making the Santa Cruz River pretty. That will include riparian restoration projects, a new bureaucracy to propose such projects, and bond elections to buy up land. The report uses fuzzy phrases such as “smart growth” and “sustainable development.” Concerning sustainability, the report admits, ” Our work during Phase I documented how elusive the concept is in practice.”

The Action Plan cites four principles for managing water:

Principle 1: Water is an essential part of life for humans and the environment. Delivery of water and wastewater must maximize both quantity and quality.

Principle 2: The environment must be considered a user, not simply a provider, of water resources.

Principle 3: Policies affecting water and wastewater must be open to wide public discussion in a completely transparent process.

Principle 4: Water is an economically-valued resource and must be managed with due consideration to its economic value.

Your comments are needed to help the City go from concepts to practice.

For some additional background, please read my posts: Water Supply and Demand in Tucson, and How Much Water is There.

The Water-Energy Nexus

Electricity is needed to get water to you, and water is needed to produce electricity. This relationship is explored in the latest issue of “Arroyo” published by the Water Resources Research Center of the University of Arizona.

This 12-page publication has some interesting and little known facts. For instance, do you know the single largest user of electricity in Arizona? It’s the Central Arizona Project which brings water to Tucson.

“Groundwater accounts for 40 percent of Arizona’s water supply. Extraction of groundwater for potable use, on average, consumes 30 percent more electricity than diversions from surface water sources, primarily because of the pumping requirements.”

In Tucson, treating wastewater consumes 1 kilowatt-hour of electricity per 1,000 gallons, while in Benson the cost is 7.3 kWh/kgal and in Patagonia it’s 13.5 kWh/kgal.

Which method of home cooling is more efficient, air conditioners or swamp coolers? “Air conditioners use between 2 to 4 times the electricity of a swamp cooler, but they do not require water. Evaporative coolers use less energy, but require continuous additions of water. The study found that if the electricity is generated by coal, the air conditioner is still a water saver, consuming only 425 gallons per month, while the swamp cooler uses more than 4,600 gallons per month. On the other hand, air conditioners are significantly more expensive to run, and their lower water footprint might not offset their greater energy consumption.” In other words, it depends.

This publication is worth the read. Download it from: http://ag.arizona.edu/azwater/files/Arroyo_2010.pdf