Climate change impacts on energy, water, and land use in the U.S.

Hibbard, K., et al. 2014: Ch. 10: Energy, Water, and Land Use. Climate Change Impacts in the United States: The Third National Climate Assessment, U.S. Global Change Research Program, 257-281.

[ Excerpts from this 25 page document, charts/tables: best to see original if you have time, this is a placeholder to make you aware it exists and whether you want to read the full article]

The links between and among energy, water, and land sectors mean that they are susceptible to cascading effects from one sector to the next.

An example is found in the drought and heat waves experienced across much of the U.S. during the summers of 2011 and 2012. In 2011, drought spread across the south-central U.S., causing a series of energy, water, and land impacts that demonstrate the connections among these sectors. Texans, for example, experienced the hottest and driest summer on record. Summer average temperatures were 5.2°F higher than normal, and precipitation was lower than previous records set in 1956. The associated heat wave, with temperatures above 100°F for 40 consecutive days, together with drought, strained the region’s energy and water resources.3,4,5 These extreme climate events resulted in cascading effects across energy, water, and land systems.

Extreme climate events result in cascading effects across energy, water, and land systems.

High temperatures caused increased demand for electricity for air conditioning, which corresponded to increased water withdrawal and consumption for electricity generation.

Heat, increased evaporation, drier soils, and lack of rain led to higher irrigation demands, which added stress on water resources required for energy production. At the same time, low-flowing and warmer rivers threatened to suspend power plant production in several locations, reducing the options for dealing with the concurrent increase in electricity demand.

The impacts on land resources and land use were dramatic. Drought reduced crop yields and affected livestock, costing Texas farmers and ranchers more than $5 billion, a 28% loss compared to average revenues of the previous four years.6 With increased feed costs, ranchers were forced to sell livestock at lower profit. Drought increased tree mortality,7 providing more fuel for record wildfires that burned 3.8 million acres (an area about the size of Connecticut) and destroyed 2,763 homes.8

The Texas example shows how energy, land, water, and weather interacted in one region. Extreme weather events may affect other regions differently, because of the relative vulnerability of energy, water, and land resources, linkages, and infrastructure. For example, sustained droughts in the Northwest will affect how water managers release water from reservoirs, which in turn will affect water deliveries for ecosystem services, irrigation, recreation, and hydropower. Further complicating matters, hydropower is increasingly being used to balance variable wind generation in the Northwest, and seasonal hydroelectric restrictions have already created challenges to fulfilling this role.

With electricity demands at all-time highs, water shortages threatened more than 3,000 megawatts of generating capacity – enough power to supply more than one million homes. 9

Competition for water also intensified. More than 16% of electricity production relied on cooling water from sources that shrank to historically low levels,9 and demands for water used to generate electricity competed with simultaneous demands for agriculture and other human activities.

Energy, land, water, and weather interactions are not limited to drought. For instance, 2011 also saw record flooding in the Mississippi basin. Floodwaters surrounded the Fort Calhoun nuclear power plant in Nebraska, shut down substations, and caused a wide range of energy, land, and water impacts (Ch. 3: Water).

GAS FRACKING: A typical shale gas well requires from two to four million gallons of water to drill and fracture (equivalent to the annual water use of 20 to 40 people in the U.S, or three to six Olympic-size swimming pools). The gas extraction industry has begun reusing water in order to lower this demand. However, with current technology, recycling water can require energy-intensive treatment, and becomes more difficult as salts and other contaminants build up in the water with each reuse.30 In regions where climate change leads to drier conditions, hydraulic fracturing could be vulnerable to climate change related reductions in water supply. The competition for water is expected to increase in the future. State and local water managers will need to assess how gas extraction competes with other priorities for water use, including electricity generation, irrigation, municipal supply, industry use, and livestock production, particularly in water-limited regions that are projected to, or become, significantly drier.

Utility-scale photovoltaic systems can require three to ten acres per megawatt (MW) of generating capacity32 and consume as much as five gallons of water per megawatt hour (MWh) of electricity production.

Utility-scale concentrating solar systems can require up to 15 acres per MW33 and consume 1,040 gallons of water per MWh34 using wet cooling (and 97% less water with dry cooling). The U.S. Department of Energy study concluded that 14% of the U.S. demand for electricity could be met with solar power by 2030.34 To generate that amount of solar power would require rooftop installations plus about 0.9 million to 2.7 million acres, equivalent to about 1% to 4% of the land area of Arizona, for utility-scale solar power systems and concentrating solar power (CSP). 34 Recognizing water limitations, most large-scale solar power systems now in planning or development are designed with dry cooling that relies on molten salt or other materials for heat transfer. However, while dry cooling systems reduce the need for water, they have lower plant thermal efficiencies, and therefore reduced production on hot days.35 Overall, as with other generation technologies, plant designs will have to carefully balance cost, operating issues, and water availability.

Biomass-based energy is currently the largest renewable energy source in the U.S., and biofuels from crops, grass, and trees are the fastest growing renewable domestic bioenergy sector.13 In 2011, approximately 40 million acres of cropland in the U.S. were used for ethanol production, roughly 16% of the land planted for the eight major field crops.37 Consumptive water use over the life cycle of corn-grain ethanol varies widely, from 15 gallons of water per gallon of gasoline equivalent for rain-fed corn-based ethanol in Ohio, to 1,500 gallons of water per gallon of gasoline equivalent for irrigated corn- based ethanol in New Mexico. In comparison, producing and refining petroleum-based fuels uses 1.9 to 6.6 gallons of water per gallon of gasoline.38,41

Carbon Capture and Sequestration (CCS) substantially increases the cost of building and operating a power plant, both through up-front costs and additional energy use during operation (referred to as “parasitic loads” or an energy penalty). 46 Substantial amounts of water are also used to separate CO2 from emissions and to generate the required parasitic energy. With current technologies, CCS can increase water consumption 30% to 100%. 48 Gasification technologies, where coal or biomass are converted to gases and CO2 is separated before combustion, reduce the energy penalty and water requirements, but currently at higher capital costs.49

CCS facilities for electric power plants are currently operating at pilot scale. Although the potential opportunities are large, many uncertainties remain, including cost, demonstration at scale, environmental impacts, and what constitutes a safe, long-term geologic repository for sequestering carbon dioxide.51

A few of the many interesting figures to look at in the original:

Figure 10.4. U.S. regions differ in the manner and intensity with which they use, or have available, energy, water, and land. Water bars represent total water withdrawals in billions of gallons per day (except Alaska and Hawai’i, which are in millions of gallons per day); energy bars represent energy production for the region in 2012; and land represents land cover by type (green bars) or number of people (black and green bars). Only water withdrawals, not consumption, are shown (see Ch. 3: Water). Agricultural water withdrawals include irrigation, livestock, and aquaculture uses.

Figure 10.5 The top panel shows water withdrawals for various electricity production methods. Some methods, like most conventional nuclear power plants that use “once-through” cooling systems, require large water withdrawals but return most of that water to the source (usually rivers and streams). For nuclear plants, utilizing cooling ponds can dramatically reduce water withdrawal from streams and rivers, but increases the total amount of water consumed. Beyond large withdrawals, once-through cooling systems also affect the environment by trapping aquatic life in intake structures and by increasing the temperature of streams.18 Alternatively, once-through systems tend to operate at slightly better efficiencies than plants using other cooling systems. The bottom panel shows water consumption for various electricity production methods. Coal-powered plants using recirculating water systems have relatively low requirements for water withdrawals, but consume much more of that water, as it is turned into steam.

Figure 10.6. The figure shows illustrative projections for 2030 of the total land-use intensity associated with various electricity production methods. Estimates consider both the footprint of the power plant as well as land affected by energy extraction. There is a relatively large range in impacts across technologies.

Figure 10.9. In many parts of the country, competing demands for water create stress in local and regional watersheds. Map shows a “water supply stress index”

Figure 10.10. Agriculture is in yellow, forests are shades of green, shrublands are gray, and urban areas are in red. The river is used for hydropower generation,


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