Category Archives: Greenhouse Gas Emissions
To generate enough electricity with solar photovoltaics to cover total energy consumption in the USA, you would need land almost equal to the size of Texas.
My brother asked me how much land you would have to cover to satisfy the demand for energy in the USA using renewables. In the previous post I constructed a “back-of-the-envelope” estimate for wind power, finding that it would require a wind farms covering land roughly equal to the size of South Carolina. In this post, I construct a similar analysis for solar power.
The largest U.S. solar farm listed in Wikipedia is Solar Star, but it has not been operational long enough to have good generating statistics posted. I will use the Topaz Solar Farm, which Wikipedia lists as the second largest in the USA.
Topaz is located in San Luis Obispo County, in California’s Central Valley. It is sited on 9.5 square miles, and its average annual generation is 1,100,000 MWh.
The amount of power generated per square mile is 1,100,000 / 9.5 = 115,789 MWh per square mile per year.
In 2014, total energy consumption in the United States was 98,385.2 trillion Btu. = 28,833,750,564 MWh.
To provide that much power would require 28,833,750,564 / 115,789 = 249,019 square miles.
How to put that in context? It is a square 499 miles on each side. It is just under the size of the state of Texas, it would occupy more than 90% of the state.
Of course, Topaz is located in California’s Central Valley, which has a strong solar resource. The Desert Southwest has an even stronger one, however, and there is a great deal of land there. Still, some of the solar farms would be likely to be spread around the country. That would put some of them in areas with weaker solar resources. In addition, this analysis does not consider the need for excess capacity, redundancy, and storage, all of which would be required to cover times when the sun doesn’t shine, thus requiring even more land. Still, my estimate gives some idea of the size of the task.
Before you boggle at the size of the task, think of our current power generating infrastructure and how long it took us to create it. In 2014 there were an estimated 7,644 power plants in the USA.
The first generating stations supplying power to the public were built in 1882, meaning that it took us 132 years to get to where we are now.
We have a big job in front of us, but if we give it our best effort, could we, would we, cover that much land with solar panels? I don’t know. But what if you relied on distributed solar photovoltaic power? What if you put solar panels on the roofs of buildings all across America? I will look at that next.
To satisfy demand for energy in the United States with wind power would require a wind farm the size of South Carolina.
My brother asked whether I had any idea how much ground would have to be covered with wind or solar farms to cover the energy consumption of the USA.
In reply, I produced the following analysis. This is obviously “back of the envelope” analysis, so be cautious how far you run with it. Still, I think it is interesting. Because some of the facts seem a bit counterintuitive, after each fact I’ve cited the source from which I got it. As you read, be sure to notice that wind power produces only electricity, yet I am comparing it to total energy consumption, which includes petroleum used in transportation.
According to Wikipedia, as of 2013 the largest wind farm in the world was the Alta Wind Energy Center, located on the eastern side of the Tehachapi Pass in the Mojave Desert. It is sited on 3,200 acres, has a rated capacity of 1,547 MW, and has a capacity factor of 30%.
A word here is needed to explain capacity factor. The rated capacity of a wind farm is its theoretical maximum generating power. However, because the wind doesn’t always blow, and turbines sometimes need maintenance, wind farms never generate their rated capacity. The average percentage of rated capacity that they actually generate is called their capacity factor. The Wikipedia article cites Alta’s capacity factor as 30%. The National Renewable Energy Laboratory says that the average capacity factor of onshore wind farms is 30-40%, with the best guess at about 37%. Capacity factor has been increasing due to improvements in turbine technology. I will use NREL’s figure.
Thus, the actual capacity of Alta would be 1,547MW * 37% = 572 MW.
There are 8,760 hours in a year. Thus, the yearly production at Alta would be 572MW * 8,760 hours = 5,010,720 MWh.
Thus, production per acre would be 5,010,720 / 3,200 = 1,567 MWh per year per acre.
In 2014, total energy consumption in the United States was 98,385.2 trillion Btu. = 28,833,750,564 MWh.
Thus, the number of acres required to meet that consumption would be 28,833,750,564 / 1,567 = 18,401,574 acres = 28,752 square miles.
How to put that in context? It is a square 170 miles on each side, or approximately 40% the size of Missouri, or roughly equal to the size of West Virginia or South Carolina. You wouldn’t want to build one contiguous wind farm, but even if you did, it would fit in West Texas, the deserts of California, or the eastern plains of Montana with ease.
Now, Alta is located in the Tehachapi Pass, which has the strongest wind resource in the nation. Wind farms located elsewhere would be located in weaker wind resources. Further, because the wind does not always blow in a given location, you would have to build excess capacity elsewhere and power storage to cover those occasions, meaning that the actual land required would be somewhat larger than my estimate. Still, it is a starting point, and it gives some sense of the size of the task involved.
Before you boggle at the size of the task, think of our current power generating infrastructure and how long it took us to create it. In 2014 there were an estimated 7,644 power plants in the USA.
The first generating stations supplying power to the public were built in 1882, meaning that it took us 132 years to get to where we are now.
We have a big job in front of us, but if we give it our best effort, what might we be able to accomplish?
In the next post, I will construct a similar analysis for solar photovoltaic.
Climate change results from greenhouse gas (GHG) emissions. Inventories of U.S. GHG emissions consistently show that the majority of our emissions consist of carbon dioxide (CO2) from burning fossil fuel to create energy. This post looks at state emissions of CO2 from burning fossil fuel to create energy. Missouri did two GHG inventories in the early 1990s, but hasn’t done one since. Thus, this data is as close as we can come to assessing Missouri’s progress in reducing GHG emissions. The most recent data is through 2013.
Figure 1 shows that in Missouri CO2 emissions from burning fossil fuel to create energy grew 13% from 2000-2005, then began a decline through 2012 that reversed most of the growth. In 2013 they began increasing again. In 2013, CO2 emissions were 4.3% above the 2000 level.
Figure 2 shows similar data for Missouri and 4 neighboring states: Arkansas, Illinois, Iowa, and Kansas. Kansas and Illinois have reduced their emissions, though only by a small amount. The other states have increased emissions, Arkansas the most at 6.6%.
Figure 3 shows change in CO2 emissions from 2000 to 2013 for all 50 states plus for the USA in total. Only 13 states have increased CO2 emissions over that period. The other 38 (list includes District of Columbia) have reduced CO2 emissions, in some instances by more than 25%. Nationwide, CO2 emissions are down 9.6%.
Figure 4 shows 2013 CO2 emissions from Missouri by Sector. The blue columns show the raw data. CO2 emissions from generating electric power dwarf those from any other sector. Electric utilities, however, don’t generate electricity for their own consumption, they generate it for others to use. The EIA keeps data on the sectors into which utilities sell their electricity, and it can be used to distribute their CO2 emissions to their end use sectors. Almost all of it goes to the Commercial, Residential, and Industrial Sectors. The red columns show the results.
The data suggest that converting electricity generation to renewable sources would probably be the the single most effective way to reduce Missouri CO2 emissions. To reduce CO2 emissions by reducing energy consumption in end use sectors, the Residential, Transportation, and Commercial sectors would all be of similar importance.
The Intergovernmental Panel on Climate Change estimates that we need to make significant reductions in CO2 emissions – 50% or more – if we are to avoid the worst effects of climate change. All states have a long way to go; most appear to have made some progress. Not Missouri.
In the coming weeks, I’m going to offer some posts that suggest that completely converting to renewable energy would require covering huge amounts of the country with wind and solar farms, without even considering the need for redundancy, excess capacity, and storage, all of which would be required. It would be a huge task.
That notwithstanding, Missouri’s performance on this metric is shameful. The fact that it is a huge, difficult task means that we aren’t going to be able to accomplish this transition overnight. We need to get cracking, and there is no excuse for avoiding it. I fear we will pay a heavy price for our inaction.
United States Energy Information Administration. 2016. Table 1: State Energy-Related Carbon Dioxide Emissions by Year (2000-2013). http://www.eia.gov/environment/emissions/state/analysis.
United States Energy Information Administration. “Sales and Revenue, 2013.” Form EIA 826 Detailed Data, Electricity. http://www.eig.gov/electricity/data/eia826/#salesrevenue.
Greenhouse gas emissions were 6,673 million metric tons of carbon dioxide equivalent (MMTCO2e) in 2013, an increase of 128 MMCO2e (2%) from 2012, reports the Environmental Protection Agency in the most recent Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2013. Figure 1 at right shows the trend since 1990. GHG emissions increased through 2007, increasing 14%. Then they decreased until 2012, decreasing 11%. Then they rose in 2013 by 2%. Compared to 1990, emissions were 372 MMTCo2e (6%) higher in 2013.
The blue areas of the columns represents carbon dioxide, showing that it is by far the largest contributor to U.S. GHG emissions. It accounts for 82.5% of all emissions. Municipal, state, national, and worldwide GHG inventories almost always show that carbon dioxide is the largest contributor to GHG emissions.
Why are humans emitting so much carbon dioxide into the atmosphere? The third chart at right gives the answer: it is emitted when we burn fossil fuel to create energy. Burning fossil fuel to create energy doesn’t just account for the largest portion of carbon dioxide emissions, fully 77% of all GHG emissions can be attributed to it. Figure 2 at right shows the data. On the chart, all of the pie slices that are blue represent emissions from burning fossil fuel to create energy. Only the green and pink slices represent other sources.
So, what are we humans doing that is using so much energy and causing so much GHG to be emitted? GHG inventories try to answer the question by categorizing emissions into economic sectors. When this is done, it almost always shows that the electric power industry is the largest emitter. Figure 3 at right shows that in the United States in 2013, the electric power industry accounted for almost 1/3 of all emissions.
Electric utilities, however, do not generate electricity for their own use in their power plants, they generate it to distribute to others. If you distribute electricity generation to the sectors where it is used, then industry was the largest producer of GHG emissions, followed closely by transportation. The data are shown in Figure 4 at right. Thus, in 2013 what Americans did most to use energy and create GHG emissions was, first, to make stuff and, second, to drive and fly around.
As noted above, after several years of decreases, in 2013 GHG emissions increased some 2%. This is not good news. The United States has made progress in establishing policies intended to reduce GHG emissions, however, compared to 1990 our emissions are still 6% higher. The best science, as reviewed by the IPCC, suggests that we need to make steep cuts in GHG emissions, or we will wreck the climate of this planet. This is not a policy blog, so I will not get into discussions of possible policy responses. However, it is clear that, if we need to make significant cuts in the amount of GHG we emit, we are not getting there yet.
Environmental Protection Agency. 2015. Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2013. Retrieved online 12/29/15 at http://www3.epa.gov/climatechange/Downloads/ghgemissions/US-GHG-Inventory-2015-Main-Text.pdf.
Kansas City, Columbia, and Creve Coeur have been among the most progressive cities in Missouri when it comes to climate change. Previously, I have reported on updates to the Columbia GHG inventory and the Creve Coeur GHG inventory. This post reports on the Greenhouse Gas Inventory Update 2013 for Kansas City. Kansas City’s original GHG inventory report studied GHG emissions in 2 years: 2000 and 2005. Comparisons between all 3 years are included in the new report.
In 2000, 2005, and 2013, total community emissions were 10.8, 11.4, and 10.5 Million Metric Tons of Carbon Dioxide Equivalent (MTCO2e). Thus, they rose initially, but then declined, with an overall decline since 2000 of 2.7%. The chart at right shows the data by what the report calls fuel source. However, “residential energy” and “commercial energy” are not fuel sources. “Electricity,” “natural gas,” and “gasoline” would be true fuel sources. The categories in the chart appear to represent what have been called “sectors” in other GHG inventory reports. Commercial Energy accounted for 27.6% of total GHG emissions, while Transportation accounted for 25.7%, and Residential Energy accounted for 24.8%.
In the Columbia GHG inventory update, we noted that growing population can invalidate direct comparisons of GHG emissions between years. In the Creve Coeur GHG inventory update, we noted that large changes in the amount of building space under roof can have the same effect. Kansas City provides per capita GHG data, but it does not provide information about any other changes in the city that might affect comparisons. On a per capita basis, Kansas City’s GHG emissions have declined by 8.9% since 2000 (see second chart at right).
The third chart at right presents true fuel source data for 2013. Electricity consumption accounted for 58% of emissions, with combined gasoline and diesel second at 25%.
Kansas City has reduced emissions from government operations significantly. From 384,000 MTCO2e in 2000, they declined to 366,000 MTCO2e in 2005, and 287,000 MTCO2e in 2013. That is a decline of 25.2%. The fourth chart at right shows the data. By far the largest source of emissions was the consumption of electricity.
The fifth chart at right shows emissions from government operations by department for 2013. While supplying water accounted for less than 1% of total community emissions, it accounted for 41% of emissions from government operations. This is a common finding among cities that operate a water utility. Public Works was the next largest, with 23% of emissions.
Like Creve Coeur, the Kansas City government has made good progress in reducing GHG emissions from its operations: 25.2%. The Kansas City community has reduced emissions by 8.9% on a per capita basis, but it has a long way to go to meet the target it set: 30% by 2030.
City of Kansas City Missouri. 2015. Greenhouse Gas Inventory Update 2013. Downloaded 2015-12-20 from https://kcstat.kcmo.org/Sustainability/2013-GHG-Inventory-5-2015-FINAL/5eqa-9amg.
Creve Coeur has been one of the most progressive cities in the St. Louis region when it comes to climate change. They were the first in the region to study their greenhouse gas emissions (GHG emissions), one of the first to adopt the U.S. Mayors Climate Protection Agreement, and one of the first to create a Climate Action Plan. Their goal, adopted in 2010, was to reduce GHG emissions 20% by 2015. Their new follow-up GHG inventory for the year 2014 is the first one in the region.
According to the update, Creve Coeur’s total emissions grew by about 0.3% between 2005 and 2014. In 2014, however, Creve Coeur was not the same city as it was in 2005: more than 2 million square feet of commercial space under roof had been added, and the population had also grown. Compared to what emissions would have been had Creve Coeur continued to emit at the same rate as in 2005 (business as usual), however, emissions were reduced about 10%. The first chart at right shows the data. (Note that the chart does not start at zero to better show the change.)
(Click on chart for larger view.)
Using the social cost of carbon as estimated by the federal government, Creve Coeur found that by reducing its emissions that much from business as usual, the city had prevented almost $2.8 million in environmental and economic damage in 2014 alone.
Fully 60% of Creve Coeur’s community emissions came from energy consumed in commercial buildings (second chart at right). Some of this energy represents energy to operate the building, and some of it represents energy used in conducting the activities that occur inside the building (refrigerators in a supermarket, for instance). Together, the built environment (commercial plus residential) account for 78% of emissions.
Emissions resulting from operations of the city government are a subset of total community emissions, but they are studied separately in a GHG inventory for 2 reasons. First, the government controls its own operations directly, while can only attempt to influence community operations through policy. Second, it helps to demonstrate leadership.
Emissions from Creve Coeur government operations were reduced by 20% from 2005 (third chart at right). Thus, the Creve Coeur government met its goal of a 20% reduction a year early. The reductions were achieved mostly through energy conservation. By reducing energy consumption, the city saved $31,022 in 2014, despite experiencing a 7% increase in energy rates.
As in 2005, the largest source of GHG emissions were the three large buildings operated by the city: the Dielmann Recreational Complex, the City Government Center, and the Public Works Garage. The fourth chart at right shows the data.
As data from municipalities in the St. Louis region continues to accrue, it becomes ever clearer that our greenhouse gases come primarily from energy consumption, and that dirty electricity is the #1 culprit. We simply must have clean energy from our electric utilities.
By reducing GHG emissions, the Creve Coeur has prevented $2.8 million in environmental damage and has reduced its energy costs by $31,022. Those benefits will accrue to the city every year it continues to abate GHG emissions. Well done Creve Coeur.
Garcia, Luis. 2015. City of Creve Coeur, Missouri Updated Greenhouse Gas Emissions Inventory for 2014. This is a public document, and hence, is available from the City of Creve Coeur, 300 N. New Ballas Rd., Creve Coeur, MO, 63141. At some point in the future it will likely be posted on their website, but it is not there yet.
Kellum, Spencer. 2008. City of Creve Coeur, Missouri Baseline Greenhouse Gas Emissions Inventory for 2005. Available on the City of Creve Coeur’s website at http://www.creve-coeur.org/DocumentCenter/Home/View/760.
This is the last post in my series on Drought in California. I’ve been writing the series for just over 3 months – I can’t believe it has been that long! I’ve looked at California’s climate, projections for how California’s climate might change through mid-century, California’s water infrastructure, California’s water supply, and patterns of water consumption in California. I’ve calculated the size of the water deficit that California might experience by mid-century, and I’ve looked at various ways California might attempt to cover the deficit: enacting policies to stop population growth, stealing water from the environment, diverting additional water from rivers, desalinating water, reducing agricultural water consumption, and reducing urban water consumption.
I’m not aware of anything like my analysis. If you are, I would love to read it, and I think other readers of this blog might like to, also. Please comment and let us know where to find it.
It looks to me like California faces some really difficult challenges. By mid-century, they are going to face a decline in water supply due to climate change. Put the decline in supply together with the fact that the population is predicted to grow, and the fact that they already overdraft their water, and they face a very large future water deficit. California has built an amazing water infrastructure, but there are problems associated with every possible alternative for covering the water deficit. Only a few seemed realistically possible to me: desalination, urban conservation, and agricultural conservation.
I constructed three scenarios for policies California might follow, but again, only one of them seemed realistic to me: conserving water in both the urban and agricultural sectors, desalinating enough water to cover the resulting urban demand, and diverting the remaining water resources to agriculture. This scenario would provide sufficient water to urban areas, but California would lose slightly more than half of its agricultural sector. I calculated the impacts such a scenario might have on California’s economy, and found that it would probably cause the economy to start shrinking. The result would be a recession, and eventually a depression. The impact would be worst in the agricultural sector, but it would be felt statewide.
The bulk of the projected water deficit comes from a decline in the snowpack that is projected to occur due to climate change. Obviously, if that projection turns out to be wrong, the entire analysis would have to change. Even if it holds true, it is likely to be a slow-motion train wreck. As I have been writing this series, an El Niño has formed, and El Niños are typically associated with lots of rain in California. It hasn’t happened yet, but many are hoping for a wet winter.
For my analysis, it doesn’t matter a bit. The projected 40% decline in the snowpack is a 30-year average. There will be wetter years, not every year will be as bad as this year. Thus, the problems I foresee are likely have a slow onset, except for economic effects. The economy depends on psychology, and asset prices do so especially. Psychology can (and usually does) change very quickly – ask anybody who invests in the stock market! At some point, I expect people to lose confidence in California. When? Before mid-century, but precisely when I don’t know. Until then, the economy will be okay. After that, it won’t. Everybody thinks they will be able to get out in time, but they never do. It is like being caught in an avalanche: there is no avalanche until the rocks are already sliding down the mountain. But then it is too late, and the avalanche slides down the mountain very fast!
As I said, I don’t know of any other analysis like mine, thus it has been a really worthwhile exercise. But it has been a lot of territory for one person to cover, especially someone who is neither an engineer, a water expert, nor a climate expert. Along the way I have had to rely on publicly available data sources. Some of them have been of the highest quality available, but others have been less reliable. There have been instances when data was not available, and I have had to make assumptions or “guesstimates.” Further, the analysis has sometimes had to predict how people will respond to the problems they will face. Predicting human behavior is notoriously hard to do. Yet if people respond differently than anticipated, the whole analysis will have to be redone.
All of these issues affect the quality of my analysis, and the reliability of my conclusions. The two areas most seriously affected are the calculation of the future water deficit and the calculation of economic effects. Take what I have written as an interesting exercise, but only the future will reveal what will actually happen.
Thanks for reading this long excursion away from what this blog usually focuses on. I’m going on vacation now for a couple of weeks. When I return in late October, I plan to get back to reporting on large-scale studies about Missouri’s environment.
This is the seventh post in my series Drought in California. In Part 1: California Climate and Drought, I found that drought is projected to be the “new normal” climate in California. In Part 2: The Status of California’s Current Water Resources, I found that California is already depleting both it’s groundwater and surface water resources. In Part 3: California’s Total Water Deficit, I constructed an overall estimate of California’s future water deficit, concluding that it will be about 25.1 million acre-feet per year, about 39% of California’s current dedicated water supply. In Part 4: The Potential to Procure Additional Ground and Surface Water, I found that a variety of obstacles and problems made it unlikely that California could cover the predicted future water deficit by tapping additional groundwater or surface water resources. In Part 5: The Potential of Desalination, I found that using desalination to cover the projected water deficit was within the realm of conceptual possibility, but it would be costly and would involve a massive infrastructure program. In Post 6: Conserving Water – Population and Environment, I discussed water consumption terminology and also concluded that conserving water by voluntarily limiting population growth or by stealing it from the environment would be objectionable due to severe negative effects.
In this post I will discuss the possibility for increasing agricultural water efficiency. At the beginning of each part of this series, I have noted that there are problems with the type of exercise I’m attempting, and with the data and analyses I’m having to use. If you want to read more about it, see the introduction to the series.
The Potential for Increased Agricultural Water EfficiencyIrrigation consumes 76% of California’s water, some 28.3 million acre-feet per year. Most of the irrigation is agricultural. (USGS, 2005) Because it is the largest consumer of water, agriculture is a prime target for water conservation. If the projected water deficit of 25.1 million acre-feet were prorated according to consumption, then 76% of the deficit would belong to agriculture, or about 19.0 million acre-feet per year. That represents about 69% of current agricultural consumption.
(Click on graphics for larger view.)
Some 77,900 California farms and ranches received $46.3 billion for their output in 2013, accounting for 12% of the national farm income total. California farms produced about 69% of the fruits and nuts produced in the USA, and 36% of the vegetables and melons. The top 10 agricultural commodities in California were (in order): milk, almonds, grapes, cattle, strawberries, walnuts, lettuce, hay, tomatoes, and nursery plants. (California Department of Agriculture, USDA) California is the sole U.S. producer (99% or more) of artichokes, dates, figs, raisin grapes, kiwifruit, olives, Clingstone Peaches, pistachios, dried plums, pomegranates, sweet rice, Ladino Clover seed, and walnuts. Thus, not only is California agriculture an essential industry within the state, but it is an essential contributor to the entire nation’s food supply. (USDA Pacific Regional Field Office, 2015)
In 2013, the average value of California farm real estate was $6,900 per acre, but irrigated land was valued at $11,800 per acre, an increase of 2.9% from 2012 (the drought is causing non-irrigated land to decline in value, but irrigated land to increase in value). The amount of land devoted to farming in California was 25.5 million acres. The total value of the farm land is about $176 billion. (USDA Pacific Regional Field Office, 2015). Direct farm employment in California in 2014 was 417,200, with an unknown number of other workers indirectly dependent on farming (anybody who sells equipment or services to farms or farmers). (Employment Development Department, 2015)
In 2012, California’s top 10 counties by production were Fresno, Kern, Tulare, Monterey, Merced, Stanislaus, San Joaquin, Kings, Ventura, and Imperial. Seven of them are in the Central Valley. Monterey County is in the Central Coast Region (John Steinbeck’s The Grapes of Wrath was set in Monterey County). Ventura County is in the South Coast Region, just north of Los Angeles. Imperial County is in the Mojave Desert, along the border with Mexico. All of these counties are dry counties – the crops depend on irrigation for survival.
The potential for increased water efficiency in California agriculture is controversial, with estimates varying widely. Theoretical calculations of potential water conservation appear to be large, but the real-world potential appears to be much smaller. For instance, focusing on the San Francisco Bay Delta, a group at the Pacific Institute wrote that up to 3.4 million acre-feet could be conserved via 4 modest strategies: crop shifting, smart irrigation scheduling, advanced irrigation management, and efficient irrigation technology. A group at the Irrigation Training & Research Center attacked the Pacific Institute paper, however. In their opinion, smart irrigation scheduling, advanced irrigation management, and efficient irrigation technology were already widely adopted on California farms. As for crop shifting, they felt that it could not be accomplished because the land was not suitable for the proposed shift, and because it would create increased supply in certain crops without creating increased demand to receive it. In addition, they felt that the Pacific Institute group had completely ignored the economic implications of their recommendations, and had fundamentally misunderstood the way in which practices on individual farms translate into basin-wide water dynamics. (Cooley, Christian-Smith, and Gleik, 2008; Burt et al, 2008.)
An instructive example of economic implications might involve nuts. Acreage devoted to the production of nuts has exploded in California: pecan acreage increased by 52% in 2013, and almond acreage increased by 33%. They are very profitable: almonds were the second leading commodity in California, and walnuts were sixth. They are a long-term crop, however: nuts grow on trees, and it takes several years before a nut tree begins producing. Thus, farmers have a significant investment of capital and time in their nut groves.
The water needs of nuts are interesting, however. They require almost 1,200 gallons of water per pound to grow (almost 9 times as much as milk, almost 3 times as much as eggs). (Mekonnen and Hoekstra, 2012) They would appear to be a good candidate for the crop shifting strategy recommended by the Pacific Institute group. Shifting, however, would require farmers to abandon their significant capital investment, as well as one of the most profitable crops in all of California.
Complicating this scenario is the arcane system of water rights that exists in most western states, including California. Water rights were established in the 1800s and early 1900s. The basis was first come, first served. The first person on the scene made a claim to withdraw a certain quantity of water from a water source. The second person did likewise, and so on. Over time, the claims accumulated. In wet years, the water resource can supply all of the claims, but not in dry years, there just isn’t enough to go around. In those years, water is not prorated. Rather, the senior claim gets the full allotment. Then the second most senior claim, then the third, and so on until there is no more to distribute. It is a controversial system, but it has existed for a very long time, and it is well established in law. (Wikipedia, Water Right)
The effect of this system is that senior water rights holders get all the water they need during dry years, while junior holders go completely without. In those years, junior holders typically allow some of their fields to lie fallow. But you can’t do that with nut trees; they need water every year, or the trees will die. Thus, junior holders may choose to plant something other than nut trees. But if you are a senior water holder, why would you shift out of nuts? You are likely to get all the water you need, it is very profitable, and if you shift, you’re going to take an economic hit. The only problem for the senior rights holder is if water distributions are cut off entirely.
Easy, inexpensive solutions like those proposed by the Pacific Institute paper are often called “low hanging fruit.” I can’t evaluate whether low hanging fruit is a real opportunity in California, or whether it is largely illusory. I do feel constrained to observe, however, that agriculture has existed in California for many decades, water scarcity has been a problem for equally as long, and California has developed the most extensive water collection and diversion system in the country. The system has been very expensive and very controversial. Given these facts, it seems that claims for easy, inexpensive solutions should be evaluated with caution. Even where water conservation is possible, it seems likely to result in increased operating costs to the farmer, and shifting to less profitable crops. Thus, farm income will be reduced.
Those who advocate increased agricultural water efficiency sometimes point to the example of Israel, a model of desert farming efficiency. Israel’s agricultural accomplishment is, indeed, admirable. However, there are important differences that may make Israel a poor model for California. For one, in Israel they don’t farm all of the various crops that they do in California. For another, it is a very small country: more than 20 Israels could fit in California, almost 3 in the Central Valley alone. Further, it is more densely populated: 4.3 times as densely populated as all of California, and 3.6 times as densely populated as the Central Valley. These differences matter, for instance, because Israel strictly limits the amount of fresh water to farms, making up for it with reclaimed water from urban areas and brackish water. The larger size of California means that infrastructure to supply reclaimed water would have to be much more extensive in California than in Israel. In addition, Israel’s higher population density means that per acre of farmland, there is more urban water available for reclamation. (Israel Export & International Cooperation Institute, 2012)
The California Legislative Analyst’s Office concluded that agricultural water efficiency could conserve about 0.5 million acre-feet of water per year, at a cost of just under $6,000 per acre-foot. (Legislative Analyst’s Office, 2008) That is a tiny fraction of the projected water deficit.
Water deliveries out of the California State Water System were cut off to many farmers in 2014, and the State Water Resources Control Board just announced further cutbacks. Water rights dating as far back as 1903 will be restricted, and restrictions will grow as the summer goes on. (Medina, 2015) The result has been the drilling frenzy discussed in Part 2 of this series, as farmers seek to maintain production by substituting groundwater. How long they can continue to do so is unknown. In Post 2 I discussed the limits of that strategy: it threatens not only to drain the aquifer, but also to harm its ability to hold water when a wetter cycle returns. In addition, a group of farmers has threatened to challenge in court the state’s ability to make such cutbacks. It is hard to believe that California would ask so many of its citizens to endure great hardship so that senior water holders could continue to grow nuts. However, the existing system of water rights is deeply and firmly entrenched in law. Taking water away from senior holders would involve taking away a very important property right. It would be highly contentious, and it is not inconceivable that the Supreme Court would rule in favor of the water holders.
Certainly, California’s agricultural sector can reduce its consumption of water. All that is required is to abandon their fields and stop farming. If this were to be the direction California follows, then the economic consequences would be hard to predict. However, if one simply assumed that, since water consumption would have to be reduced by 67%, then 67% of California’s agricultural production would be lost, and 67% of the farmland would be lost, and it would amount to a loss of $31 billion in annual farm receipts, and $118 billion in farmland, not to mention all the equipment on those farms. About 280 thousand people would be thrown out of work. I don’t know how many of those whose lives are indirectly dependent on farming would become unemployed, but if one assumes that it would be 1/3 as many, then some 372 thousand people would be unemployed in total. That represents about 2% of California’s civilian employment, though the unemployment would be concentrated in the agricultural counties, not spread throughout the state. And finally, farmers usually operate on bank credit. The failure of 67% of the farms in California would create significant strains on the banking system, and the recent Great Recession has shown us how much havoc stress on the banking system can create.
The above paragraph makes it sound like the effects would all occur at once, in one year. If the drought and lack of snowpack continue as they have the last two years, the effects may, indeed, be concentrated into a single year, or two, or three. But if a wetter cycle returns, with the decline in the snowpack occurring gradually through mid-century, then the effects would be more gradual, spread over many years.
In summary, agriculture is the largest consumer of water in California. The sector’s prorated share of the water deficit would amount to slightly more than 2/3 of its current water consumption. While nobody is claiming that the sector can make that big a reduction in water consumption, there are a variety of sources claiming that large improvements in California’s agricultural water efficiency are easily and affordably achievable. However, there is reason for skepticism, and the conclusion of the Legislative Analyst’s Office is that only a very small improvement is achievable.
The alternative would be for a large portion of California’s agriculture to be lost, resulting in loss of income, loss of assets, stress on the banking system, and possibly a 2% increase in unemployment statewide. In addition, the entire United States would feel the effects, as more than 5% of our food supply would be lost, including 22% of our supply of vegetables and melons, and about 46% of our fruits and nuts.
My best guess, and it is mostly a guess, is that if cooperation occurs, then some water conservation will be achievable, more than the amount estimated by the Legislative Analysts Office. However, it will be nowhere the amount needed to cover the projected deficit. I have no idea how the issue of water rights will be resolved, but I expect that it will be highly contentious. I expect that a significant amount of California’s agricultural output will be lost, and a significant portion of its farms will fail and be abandoned. I expect that the effects will ripple through the communities which depend on and support California’s agriculture, causing significant hardship and economic dislocation. Over what period of time all this will occur depends on how the drought continues to unfold, as well as many human factors.
Burt, Charles, Peter Canessa, Larry Schwankl, and David Zoldoske. 2008. Agricultural Water Conservation and Efficiency in California – A Commentary. Unpublished paper. Retrieved online 6/12/15 at http://www.itrc.org/papers/commentary.htm.
California Department of Food and Agriculture. California Agricultural Production Statistics. Web page accessed 6/12/15 at http://www.cdfa.ca.gov/statistics.
Cooley, Heather, Juliet Christian-Smith, and Peter Gleick. 2008. More With Less: Agricultural Water Conservation and Efficiency in California. Oakland, CA: Pacific Institute. Retrieved online 6/12/15 at http://www.pacinst.org/wp-content/uploads/sites/21/2013/02/more_with_less3.pdf.
Employment Development Department. 2015. Industry Employment & Labor Force – by Annual Average. An Excel spreadsheet created 5/22/15 by the Labor Market Information Division of the California Employment Development Department, and downloaded 6/14/15 at http://www.labormarketinfo.edd.ca.gov/LMID/Employment_by_Industry_Data.html.
Israel Export & International Cooperation Institute. 2012. Israel’s Agriculture. Retrieved online at http://www.moag.gov.il/agri/files/Israel%27s_Agriculture_Booklet.pdf.
Legislative Analyst’s Office. 2008. California’s Water: An LAO Primer. Retrieved online at http://www.lao.ca.gov.
Medina, Jennifer. 6/12/15. “California Cuts Farmers’ Share of Scant Water.” New York Times. Retrieved online 6/14/15 at http://www.nytimes.com/2015/06/13/us/california-announces-restrictions-on-water-use-by-farmers.html?ref=earth&_r=0.
Mekonnen and Hoekstra. 2012. “A Global Assessment of the Water Footprint of Farm Animal Products. Ecosystems. 15: 401-415. Downloaded from http://waterfootprint.org/media/downloads/Mekonnen-Hoekstra-2012-WaterFootprintFarmAnimalProducts.pdf.
USDA. “Cash Receipts by Commodity, 2010-2014F.” U.S. and State-Level Farm Income and Wealth Statistics. Economic Research Service. Web data portal accessed 6/12/15 at http://www.ers.usda.gov/data-products/farm-income-and-wealth-statistics/annual-cash-receipts-by-commodity.aspx.
USDA Agricultural Research Service. “Blue Orchard Bee.” http://www.ars.usda.gov/Research/docs.htm?docid=18333.
USDA Pacific Regional Field Office, California. 2015. California Agricultural Statistics 2013 Annual Bulletin. Sacramento, CA: Pacific Regional Field Office, National Agricultural Statistics Service. Available online at http://www.nass.usda.gov/Statistics_by_State/California/Publications/California_Ag_Statistics/2013cas-all.pdf.
USGS. Estimated Use of Water in the United States. County Level Data for 2005. http://water.usgs.gov/watuse/data/2005.
Wikipedia. Water right. Viewed online 6/12/2015 at https://en.wikipedia.org/wiki/Water_right.
This is the sixth post in my series Drought in California. In Part 1: California Climate and Drought, I found that drought is projected to be the “new normal” climate in California. In Part 2: The Status of California’s Current Water Resources, I found that California is already depleting both it’s groundwater and surface water resources. In Part 3: California’s Total Water Deficit, I constructed an overall estimate of California’s future water deficit, concluding that it will be about 25.1 million acre-feet per year, about 39% of California’s current dedicated water supply. In Part 4: The Potential to Procure Additional Ground and Surface Water, I found that a variety of obstacles and problems made it unlikely that California could cover the predicted future water deficit by tapping additional groundwater or surface water resources. In Part 5: The Potential of Desalination, I found that using desalination to cover the projected water deficit was within the realm of conceptual possibility. However, it would involve a massive infrastructure construction program. Whether such a program could be completed within the needed time frame was unknown. Further, desalinating such a large volume of water would have an annual cost roughly equal to 1% of California’s total GDP.
This post will examine the potential for water conservation by limiting population growth and by limiting environmental uses of water. At the beginning of each part, I have noted that there are problems with the type of exercise I’m attempting, and problems with the data and analyses I’m having to use. If you want to read more about them, see the introduction to the series.
The Basics of Water Consumption
Water consumption gets a bit complex, and one needs a little foundation to understand it. The water literature uses several terms to discuss water use. Total supply is all of the water that comes into the state, by whatever route Dedicated supply is that portion of total supply that is available for human use. Withdrawals refer to water taken from the dedicated supply and used for human purposes. Consumptive withdrawals are used in a way that makes the water unavailable for use in the same water basin. Such a use might involve evaporation, conversion to steam that is lost to the atmosphere, or contamination. Non-consumptive withdrawals return the water to the basin in a way that it can be used again. An example might be irrigation water that either sinks into the ground and then into an aquifer that is tapped by wells, or that flows into a collection pond from which it is used again.
In Part 2 of this series I reported that the California Department of Water Resources estimated dedicated supply to be 65.1 million acre-feet in 2001, a dry year. Figure 5b, repeated from that post, shows the uses to which that water was distributed.
(Click on graphics for larger view.)
Total water withdrawals in California during 2005 were about 51.2 million acre-feet per year. About 28% of California water was withdrawn for thermoelectric generation, which parallels findings in other states. Figure 22a shows the amounts by sector, with withdrawals for thermoelectric generation included. Figure 22b shows the same data with withdrawals for thermoelectric generation excluded. With thermoelectric generation excluded, irrigation accounted for about 76% of all water withdrawals in California. Industrial use (including mines) consumed a mere 1%. Domestic withdrawal is water used in homes. The bulk of it is supplied by public water supply companies, but a small amount is self-supplied, as in a home well. Public supply is water delivered by a state certified public water utility. Most of the water delivered for urban use comes from public supply. In 2005 about 57% of publicly supplied water was delivered to homes, with about 43% going to commercial and other uses. (USGS, 2005)
Why have I netted out water withdrawn for thermoelectric generation? Because it is one of those non-consumptive withdrawals discussed above. Nuclear and coal power plants use huge volumes of cooling water. The cooling water is typically returned to the environment. It may cause local problems because it is hot, but it is not usually otherwise polluted. In this sense, it is used, but not consumed.
Could California reduce water consumption by limiting population growth or by limiting the amount of water returned to the environment?
When I constructed an estimate of California’s future water deficit in Part 3, about 3.1 million acre-feet of it was based on population growth. Should the population stop growing, it would reduce the projected deficit by that much. Figure 23 shows California’s decadal population growth rate in blue, and the USA’s in red. California’s rate of growth has declined over time, and between 2000 and 2010, California’s population grew 10%, the same as the USA as a whole. (U.S. Census Bureau (a), U.S. Census Bureau (b))
To conserve water, California could enact policies to reduce, halt, or reverse population growth. The idea would likely encounter significant resistance, however. Businesses and governments generally assume population decline to be socially and economically destructive, and over the last several decades several countries around the world have taken steps to reverse slowing rates of population growth because of these concerns. (Coleman and Rowthorn, 2011) In addition, policies to limit population growth fairly and equitably would be complex to devise. Some policies, such as the one child policies in China and India, have been oppressive, if not brutal.
It seems unlikely that California will voluntarily enact policies to intentionally limit population growth; it would be extraordinarily controversial. Besides, only 12% of the projected water deficit was based on population growth, and limiting population would do nothing to address the remaining 88%.
I personally believe, however, that the projected water deficit facing California will cause an involuntary reduction in California’s population. I believe that California will become a much less desirable place to live or to locate a business. There will be a net outmigration, just as there was a migration out of the Midwest during the Dust Bowl. This possible scenario will be discussed in more detail in a coming post.
Returning Water to the Environment
The estimate of dedicated supply (65.1 million acre-feet, see Part 2 of this series) is larger than the estimate of net withdrawals by 28 million acre-feet. That’s a lot of water! There are several reasons for the difference. First, supply is different from consumption; the estimates are constructed using entirely different data sets. You wouldn’t expect them to agree perfectly. Second, dedicated supply was estimated for 2001, while withdrawals were estimated for 2005. While both were dry years, it is likely that the total supply was different, and that affected both dedicated supply and withdrawals. Most important, however, is that 35% of the dedicated supply was returned to the environment for environmental remediation purposes. The supply data from the California Department of Water Resources included this water, but the USGS data on withdrawals did not.
From time-to-time I read a proposal that to solve the water deficit, California should simply stop using water for environmental purposes. Of California’s 65.1 million acre-feet of dedicated supply in 2001, some 22.4 million acre-feet of it were used for environmental purposes. That is close to being enough to cover the future deficit I projected.
There would be problems with this proposed solution, however. For instance, the largest single environmental return is water diverted into the San Francisco Bay Delta. In their natural states, the Sacramento and San Joaquin Rivers provide sufficient flow of fresh water through the delta into San Francisco Bay to prevent ocean water from the bay from intruding into the delta. However, so much water has been diverted from these streams that ocean water threatens to intrude. The water in the California State Water Project that is destined for Southern California is discharged into the delta by the Sacramento River, flows across the delta, and is sucked up by huge pumps on the other side, lifting it into the California Aqueduct, and sending it south. If water were not returned to the delta, salt water would contaminate the water destined for Southern California. Even with water returns, the drought has reduced water flow through the delta to the point that the California State Water System is having to construct an emergency barrier in the delta to prevent salt intrusion. (California Department of Water Resources, 5/29/15)
The situation with the delta is an example of a general principal: water returned to the environment is not wasted, it is used to prevent serious environmental damage. Now, there are places around the world where people have chosen to proceed with unwise water diversions, and they have devastated the environment as a result. Perhaps the Aral Sea is the most dramatic example. Once the world’s fourth largest lake, it has been reduced by water diversion to a small fraction of its former extent. The entire region’s climate has been adversely effected, thousands of square miles of barren salt flats have been created, the regions economy has been devastated, and Kazakhstan has begun an expensive emergency program to try to restore the sea. It has been called one of the world’s worst environmental disasters. (Wikipedia, Aral Sea)
California already over-withdraws water from its rivers, causing environmental damage. Would the state choose to turn itself into another Aral Sea? Would it be allowed to do so? I doubt it. I do not believe that significant additional water can be obtained by taking it from the environment.
Thus, it seems unlikely that California will pursue a policy to voluntarily and intentionally limit population. And it seems clear that California cannot pursue a policy of withdrawing additional water from the environment without serious environmental harm. “Environmental harm,” of course, is a euphemism for some really unpleasant stuff, as they found out around the Aral Sea.
This post was corrected on 8/8/15 to correct an error in Figure 22b.
California Department of Water Resources (b). California State Water Project Water Supply. Webpage accessed 5/21/2015 at http://www.water.ca.gov/swp/watersupply.cfm.
California Department of Water Resources. 5/29/15. Emergency Drought Barrier Nears Completion. News release viewed online 6/12/15 at http://www.water.ca.gov/news/newsreleases/2015/052915.pdf.
Coleman, David, and Robert Rowthorn. 2011. “Who’s Afraid of Population Decline? A Critical Examination of Its Consequences.” Population and Development Review. (37), Issue Supplement s1, 217-248. Retrieved online 6/6/15 at http://www.oisp.ox.ac.uk/fileadmin/documents/PDF/WP57_Who_s_afraid_of_population_Decline__by_David_Coleman_and_Robert_Rowthorn.pdf.
NASA. 2005. Sacramento River Delta. Earth Observatory, 12/2/2005. http://earthobservatory.nasa.gov/IOTD/view.php?id=6070.
U.S. Census Bureau (a). Part II. Population of the United States and Each State: 1790-1990. http://www.census.gov/population/www/censusdata/Population_PartII.xls.
U.S. Census Bureau (b). Table 1. Intercensal Estimates of the Resident Population for the United States, Regions, States, and Puerto Rico: April 1, 2000 to July 1 , 1010. http://www.census.gov/popest/data/intercensal/national/nat2010.html.
USGS. Estimated Use of Water in the United States. County Level Data for 2005. http://water.usgs.gov/watuse/data/2005.
USGS/NASA. Satellite imagery of the Aral Sea. Visualization by UNEP/GRID-Sioux Falls. Downloaded 6/16/15 from http://na.unep.net/geas/getUNEPPageWithArticleIDScript.php?article_id=108.
Wikipedia. Aral Sea. Viewed online 6/15/15 at https://en.wikipedia.org/wiki/Aral_Sea.
This post is Part 3 of my series on Drought in California. In Drought and the California Climate, published 2 weeks ago, I reviewed the drought California is experiencing, the state’s historical climate, and projections for the state’s future climate. I discovered that drought is expected to become the “new normal” for the state. In The Status of California’s Current Water Resources, published last week, I surveyed California’s current water resources, discovering that California is already experiencing deficits in both groundwater and surface water. Both groundwater and surface water supplies are being depleted. Unless changes are made, the depletion is projected to continue.
This post attempts to construct a summary total of California’s overall water deficit. The estimate is going to be a very rough, “back-of-the-envelope” exercise, that relies on a number of assumptions that may, or may not, be correct. Nevertheless, such an estimate is needed in order to evaluate potential measures to procure additional water supplies and to conserve existing ones. There are surprisingly few published estimates out there. They are uneven in what they include and omit. Indeed, much of the data and the analysis used for this series have problems and limitations. You can read about them in the introduction to the series.
California’s Total Water Deficit
As noted in the previous post, the total water supply for California has been estimated for wet, average, and dry years. Because climate change is expected to cause drought to be the “new normal” in California, the supply during dry years is the one that should be of most interest to us.
In addition, either the total supply or the dedicated supply can be estimated. The total supply is an estimate of every drop of water that falls on the state as precipitation, every drop that is imported in aqueducts from other states, every drop that is desalinated, and every drop that is pumped out of the ground. The dedicated supply is the portion available for human consumption. The not-dedicated water is not surplus; it recharges aquifers, and supports the plants, animals, and fish that live in California. Thus, it is not an untapped water supply available for humans to grab. The dedicated supply is the estimate that is relevant to these calculations. As noted in the previous post, the dedicated supply of water during a dry year is 65.1 million acre-feet. (California Department of Water Resources (b)).
Table 3 at right shows how the dedicated water supply is used in wet, average, and dry years. The table shows that in dry years, the amount of water distributed by the California State Water Project to agriculture and to urban uses actually increases. But the amount distributed to environmental uses decreases by almost 1/3. This is not difficult to understand: they close the sluice gates. More water is held in the reservoirs and diverted into the aqueducts, less flows into the rivers.
(Click on graphics for larger view.)
California currently derives its water from two primary sources: groundwater and surface water. Groundwater comes from aquifers. The largest and most important fresh water aquifer in California is the Central Valley Aquifer. Its status was reviewed in the previous post. As it is the most important aquifer, I will let its deficit stand in for the total groundwater deficit, though it is surely an underestimate. Water storage in the Central Valley Aquifer declined by at least 114 million acre-feet between 1962 and 2014. That is about 2.2 million acre-feet per year. Withdrawals would have to be curtailed by that much to stabilize the aquifer. (May, 2015)
An analysis by the Pacific Institute and the National Resources Defense Council estimates that California diverts 5 million more acre-feet from the Sacramento-San Juan watershed than can be sustained, and depletes up to 2 million acre-feet from that watershed’s groundwater supplies. It is not clear how this study’s estimated groundwater deficit overlaps with the Central Valley Aquifer decline estimated above, but I will assume that half of it does, and the Pacific Institute estimate should be adjusted by that amount. Thus, the overall estimated deficit is 6 million acre-feet. (Pacific Institute and the NRDC, 2014)
The EPA estimates that California’s groundwater deficit in 2010 was 2 million acre-feet per year. Given current trends, population growth in California will result in an additional 6.2 million acre-feet deficit in a drought year. The current deficit of 2 million acre-feet appears to overlap with the estimate by the Pacific Institute, and will not be included further in this calculation. The future estimate appears to be an estimate of increased demand caused by the anticipated increase in population. For many years, California’s booming economy has depended on a growing population, and it seems unlikely that economic interests will want to freeze or reduce it. It seems equally unlikely, however, that the trend can continue unchanged. Thus, because population growth may slow, it may be reasonable to reduce the EPA’s estimated deficit. By how much is not clear, but by 50% may be reasonable. That would be 3.1 million acre-feet. (EPA, 2010)
Neither the Pacific Institute estimate nor the EPA estimate attempts to assess the effects of reservoirs going dry, or of a significant decline in the snowpack. Were Lake Mead to go dry, it would interrupt water deliveries from the Colorado River System. Although the intakes for the aqueducts that deliver the water are in Lake Havasu, if Lake Mead were to go dry, it would disrupt managers’ ability to manage the water level in Lake Havasu, uncovering the intakes. The system provides about 4.4 million acre-feet per year to the state, and this would represent an immediate loss of that supply. For Southern California’s metro areas, it would represent a loss of about 23% of their water supply. The loss of one or more of California’s instate reservoirs would be only slightly less catastrophic. I don’t have an estimate of when that might occur, however, so it will not be included in this calculation. Recall from the previous post that even a 25% reduction in water withdrawals still left a 50% chance that Lake Mead would go dry by 2060. Thus, the draw from the Colorado River would need to be reduced by more than that. How much more is unclear, but again, a 50% reduction seems not unreasonable. That would be 2.2 million acre-feet. (Barnett and Pierce, 2008)
In 2015 the California snowpack was only 5% of its historical average. If this were to become the normal occurrence, it would represent an immediate and existential threat to the state. Not only would runoff into the streams that charge California’s man-made reservoirs be reduced, but water seeping into the ground to recharge the aquifers would, also. However, the 2015 snowpack may be a temporary extreme, and it may be better to accept the National Climate Assessment’s projection of an average 40% decline in the water content of the snowpack (discussed in Part 1). That would amount to 11.6 million acre-feet.
It is difficult to know how to combine this information into an overall estimate of California’s looming water shortage. It seems that only the National Climate Assessment anticipates a decline in water supply based on the decline in the snowpack, and none of the estimates discuss the need to reverse the already-occurring depletion of essential reservoirs.
The estimated deficit in the Central Valley Aquifer is 2.2 million acre-feet per year. The Pacific Institute’s estimate for this same region overlaps with this estimate by about 1 million acre-feet per year, but adds surface water deficits. Adjusting the Pacific Institute estimate to reflect the overlap, the deficit is estimated at 6 million acre-feet per year. These two estimates pertain to only part of the state, the Central Valley. However, that watershed is by far the state’s largest and most important. The aquifer and the two rivers there are the largest within the state. A large part of the excluded area is very dry, and water from the two Central Valley rivers is delivered far and wide across the state. Therefore, these two estimates appears to be a minimum, but reasonable starting point. The EPA’s estimate (adjusted to remove overlap with the Pacific Institute and to anticipate a reduced rate of population growth) represents the increase in demand that would come from an increase in population. It would be 3.1 million acre-feet per year. To prevent Lake Mead from going dry would require a 2.2 million acre-feet reduction. Finally, by far the largest of these potential water deficits would be the decline in the snowpack, which would be 11.6 million acre-feet. (U.S. Global Change Research Program, 2014)
Combined, they sum to a total water deficit of 25.1 million acre-feet, about 39% of California’s dedicated water supply in dry years. Thus, I estimate that to remove its future water deficit, California will need to increase supply and/or reduce demand by more than 1/3.
This estimate is much larger than currently published estimates. The primary reason is that I have included both population growth and the projected effects of climate change. If population growth and climate change trends were to change, it would impact the estimate. In addition, though I remarked on the limitations of this analysis at the beginning, I feel I should restate that the analysis relies on a number of assumptions that may or may not be correct, and on data that is far from perfect.
California can contribute to minimizing the impacts of climate change, but no single state is in control of climate change. California will have to adjust. The estimate constructed above provides one perspective on just how much adjusting they will have to do. In coming posts, I will explore potential strategies for increasing water supply and/or reducing demand.
Barnett, Tim, and David Pierce. 2008. “When Will Lake Mead Go Dry?” Water Resources Research, 44, W03201. Retrieved online at http://www.image.ucar.edu/idag/Papers/PapersIDAGsubtask2.4/Barnett1.pdf.
California Department of Water Resources (b). California State Water Project Water Supply. Web page accessed 5/21/2015 at http://www.water.ca.gov/swp/watersupply.cfm.
EPA. 2010. “California Water Fact Sheet.” EPA WaterSense. EPA832-F-10-016. http://www.epa.gov/watersense/docs/california_state_fact_sheet.pdf.
May, John. 2015. “The Status of California’s Current Water Resources.” Blog post in the blog MoGreenStats. http://www.mogreenstats.com.
Pacific Institute and the National Resources Defense Council (NRDC). 2014. The Untapped Potential of California’s Water Supply: Efficiency, Reuse, and Stormwater. http://pacinst.org/publication/ca-water-supply-solutions/#issuebriefs.
U.S. Global Change Research Program. 2014. Climate Change Impacts in the United States: The Third U.S. National Climate Assessment. http://www.nca2014.globalchange.gov.