Drought in the United States:
Causes and Issues for Congress
Peter Folger
Specialist in Energy and Natural Resources Policy
Betsy A. Cody
Specialist in Natural Resources Policy
Nicole T. Carter
Specialist in Natural Resources Policy
June 12, 2012
Congressional Research Service
7-5700
www.crs.gov
RL34580
CRS Report for Congress
Pr
epared for Members and Committees of Congress
Drought in the United States: Causes and Issues for Congress
Summary
Drought is a natural hazard with potentially significant societal, economic, and environmental
consequences. Public policy issues related to drought range from how to identify and measure
drought to how best to prepare for, respond to, and mitigate drought impacts, and who should
bear such costs. This report provides information relevant to drought policy discussions by
describing the physical causes of drought, drought history in the United States, examples of
regional drought conditions, and policy challenges related to drought.
What is drought? Drought is commonly defined as a lack of precipitation over an extended period
of time, usually a season or more, relative to some long-term average condition. While the
technology and science to predict droughts have improved, regional predictions remain limited to
a few months in advance. History suggests that severe and extended droughts are inevitable and
part of natural climate cycles.
What causes drought? The physical conditions causing drought in the United States are
increasingly understood to be linked to sea surface temperatures (SSTs) in the tropical Pacific
Ocean. Studies indicate that cooler-than-average SSTs have been connected to the severe western
drought in the first decade of the 21st century, severe droughts of the late 19th century, and
precolonial North American “megadroughts.” The 2011 severe drought in Texas is thought to be
linked to La Niña conditions in the Pacific Ocean.
What is the future of drought in the United States? The prospect of extended droughts and more
arid baseline conditions in parts of the United States could suggest new challenges to federal
water projects, which were constructed largely on the basis of 20th century climate conditions.
Some studies suggest that the American West may be transitioning to a more arid climate,
possibly resulting from the buildup of greenhouse gases in the atmosphere, raising concerns that
the region may become more prone to extreme drought it was in the 20th century. Some models of
future climate conditions also predict greater fluctuations in wet and dry years.
California’s 2007-2009 drought exacerbated ongoing tensions among competing water uses.
While drought is most common in California and the Southwest, drought also can exacerbate
water tensions in other regions. For example, the 2007-2008 drought in the Southeast heightened
a long-standing dispute in the Apalachicola-Chattahoochee-Flint River (ACF) basin. Both
California and the ACF are again experiencing drought conditions, as are the Rio Grande and
Upper Colorado River basins.
What are some drought policy challenges? Although the impacts of drought can be significant
nationally as well as regionally, comprehensive national drought policy does not exist.
Developing such a policy would represent a significant challenge because of split federal and
non-federal responsibilities, the existing patchwork of federal drought programs, and differences
in regional conditions and risks. While a comprehensive national policy has not been enacted,
Congress has considered and acted upon some of the recommendations issued by the National
Drought Policy Commission in 2000. In coming years, Congress may review how federal
agencies such as the U.S. Army Corps of Engineers and the Bureau of Reclamation respond to
droughts. Congress may also assess other federal programs or choose to reassess the National
Drought Policy Commission’s recommendations.
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Contents
Introduction...................................................................................................................................... 1
What Is Drought?............................................................................................................................. 2
Drought Is Relative.................................................................................................................... 2
Drought Is Multifaceted ............................................................................................................ 4
Drought Classification............................................................................................................... 4
Recent Examples: Texas, California, and Upper Colorado River Basin ................................... 5
Drought in Texas—2011 and 2012...................................................................................... 5
The 2007-2009 California Drought and Outlook for 2012 ................................................. 7
The 2012 Conditions in the Upper Colorado River Basin .................................................. 8
What Causes Drought in the United States? .................................................................................... 9
Prehistorical and Historical Droughts in the United States ..................................................... 11
Responding to and Planning for Drought ...................................................................................... 12
Federal Aid .............................................................................................................................. 12
Federal Facilities and Drought ................................................................................................ 13
Drought Forecasts for the United States ........................................................................................ 15
Policy Challenges .......................................................................................................................... 17
Legislative Action.................................................................................................................... 19
The National Drought Policy Act of 1998......................................................................... 19
National Drought Preparedness Legislation and the 2008 Farm Bill................................ 20
National Integrated Drought Information System............................................................. 20
Conclusion ..................................................................................................................................... 21
Figures
Figure 1. Extent of Drought in the United States on May 8, 2012 .................................................. 3
Figure 2. Comparison of Drought Conditions in Texas in 2010, 2011, and 2012 ........................... 5
Appendixes
Appendix. Excerpt from the 2000 National Drought Policy Commission Report to
Congress ..................................................................................................................................... 22
Contacts
Author Contact Information........................................................................................................... 22
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Drought in the United States: Causes and Issues for Congress
Introduction
The likelihood of extended periods of severe drought, similar to conditions experienced centuries
ago, and its effects on 21st century society in the United States raise several issues for Congress.
Drought often results in significant agricultural losses, which can have widespread effects. It also
can impact other industries and services, including power and energy resource production,
navigation, recreation, municipal water supplies, and natural resources such as fisheries and water
quality. Addressing drought impacts on an emergency basis is costly to individuals, communities,
and businesses. Additionally, hundreds of millions and sometimes billions of dollars in federal
assistance can be expended in attempting to manage drought’s social consequences.
Drought has afflicted portions of North America for thousands of years. Severe, long-lasting
droughts may have been a factor in the disintegration of Pueblo society in the Southwest during
the 13th century, and in the demise of central and lower Mississippi Valley societies in the 14th
through 16th centuries.1 In the 20th century, droughts in the 1930s (Dust Bowl era) and 1950s were
particularly severe and widespread. In 1934, 65% of the contiguous United States was affected by
severe to extreme drought.2
Drought conditions are broadly grouped into five categories: (1) abnormally dry, (2) moderate,
(3) severe, (4) extreme, and (5) exceptional.3 Some part of the country is almost always
experiencing drought at some level. Since 2000, no less than 7% of the land area of the United
States has experienced drought of at least moderate intensity each year.4 The land area affected by
drought of at least moderate intensity varies by year and also within a particular year. For
example, since 2000, the total U.S. land area affected by drought of at least moderate intensity
has varied from as little as 7% (August 3, 2010) to as much as 46% (September 10, 2002). Based
on weekly estimates of the areal extent of drought conditions since 2000, the average amount of
land area across the United States affected by at least moderate-intensity drought has been 25%.
While the previous percentages refer to the extent of drought nationally, there is particular
concern about those locations experiencing the most intense drought conditions. Nearly every
year, extreme drought5 affects some portion of the country. Since 2000, extreme drought or drier
conditions have affected approximately 6% of the nation on average.6 During August 2002,
extreme drought extended over 19% of the country. Since 2000, exceptional drought conditions
have affected approximately 1% of the nation on average. Of particular note were the conditions
1 Edward R. Cook, Richard Seager, Mark A. Crane, and David W. Stahle, “North American drought: reconstructions,
causes, and consequences,” Earth-Science Reviews, vol. 81 (2007): pp. 93-134. Hereafter referred to as Cook et al.,
2007.
2 Donald A. Wilhite, et al., Managing Drought: A Roadmap for Change in the United States (Boulder, CO: The
Geological Society of America, 2007), p. 12; at http://www.geosociety.org/meetings/06drought/roadmap.pdf.
3 These are the categories used by the National Drought Mitigation Center (NDMC). The NDMC helps prepare the
U.S. Drought Monitor and maintains its website.
4 NDMC data collected since 2000. U.S. Drought Monitor at the NDMC in Lincoln, NE. See
http://droughtmonitor.unl.edu/dmtabs_archive.htm.
5 Extreme drought is the fourth of five categories indicating drought conditions, ranging from abnormally dry to
exceptional drought, according to the National Drought Mitigation Center.
6 In some years or months, however, no part of the country was under extreme or exceptional drought. For example,
from January 2000 through early April 2000, extreme or exceptional drought did not affect any portion of the country.
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between June and October 2011; exceptional drought occurred over the largest land area—greater
than 9%—during those months, with the affected areas concentrated in Texas.
This report discusses how drought is defined (e.g., why drought in one region of the country is
different from drought in another region), and why drought occurs in the United States. How
droughts are classified, and what is meant by moderate, severe, and extreme drought
classifications, are also discussed. The report briefly describes periods of drought in the country’s
past that equaled or exceeded drought conditions experienced during the 20th century. This is
followed by a discussion of the future prospects for a climate in the West that would be drier than
the average 20th-century climate. The report concludes with a primer on policy challenges for
Congress, such as the existing federal/non-federal split in drought response and management and
the patchwork of drought programs subject to oversight by multiple congressional committees.
An exhaustive discussion of each policy challenge facing Congress is beyond the scope of this
report.
What Is Drought?
Drought has a number of definitions; the simplest may be a deficiency of precipitation over an
extended period of time, usually a season or more.7 Drought is usually considered relative to
some long-term average condition, or balance, between precipitation, evaporation, and
transpiration by plants (evaporation and transpiration are typically combined into one term:
evapotranspiration).8 An imbalance could result from a decrease in precipitation, an increase in
evapotranspiration (from drier conditions, higher temperatures, higher winds), or both. It is
important to distinguish between drought, which has a beginning and an end, and aridity, which is
restricted to low rainfall regions and is a relatively permanent feature of climate (e.g., deserts are
regions of relatively permanent aridity).9
Higher demand for water for human activities and vegetation in areas of limited water supply
increases the severity of drought. For example, drought during the growing season would likely
be considered more severe—in terms of its impacts—than similar conditions when cropland lies
fallow. For policy purposes, drought often becomes an issue when it results in a water supply
deficiency: Less water is available than the average amount for irrigation, municipal and
industrial supply (M&I), energy production, preservation of endangered species, and other needs.
At the national level, drought is monitored and reported by the National Drought Mitigation
Center in an index known as the U.S. Drought Monitor, which synthesizes various drought
indices and impacts, and represents a consensus view of ongoing drought conditions between
academic and federal scientists.
Drought Is Relative
Drought and “normal” conditions can vary considerably from region to region. For example, in
May 2012, the cities of Lubbock, TX, and Athens, GA, were within areas of extreme drought,
7 NDMC, http://www.drought.unl.edu/DroughtBasics/WhatisDrought.aspx.
8 Evapotranspiration may be defined as the loss of water from a land area through transpiration from plants and
evaporation from the soil and surface water bodies such as lakes, ponds, and manmade reservoirs.
9 Permanently arid conditions reflect the climate of the region, which is the composite of the day-to-day weather over a
longer period of time. Climatologists traditionally interpret climate as the 30-year average. See NDMC,
http://www.drought.unl.edu/DroughtBasics/WhatisClimatology.aspx.
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according to the U.S. Drought Monitor.10 (See Figure 1.) However, extreme drought means
something different to Lubbock, in northwest Texas, than it does for Athens, in north central
Georgia. Lubbock receives an average total of 3.26 inches of precipitation for the three-month
period from February through April of each year.11 In contrast, Athens receives an average of
12.06 inches over the same time period.12 From February 2012 through April 2012, Athens
received 6.03 inches, which equates to 1.85 times the average precipitation normally received in
Lubbock over that time period, but is only 50% of what Athens receives on average. Both cities
faced extreme drought compared to normal conditions, but what defines normal for each city
differs substantially.
To deal with these differences, meteorologists use the term meteorological drought—usually
defined as the degree of dryness relative to some average amount of dryness and relative to the
duration of the dry period. Meteorological drought is region-specific because atmospheric
conditions creating precipitation deficiencies vary from region to region, as described above for
Lubbock and Athens.
Figure 1. Extent of Drought in the United States on May 8, 2012
Source: U.S. Drought Monitor, at http://droughtmonitor.unl.edu/, May 8, 2012. Modified by CRS.
Note: The areas delineated on the map as “drought impact types” depict regions where reports of specific
impacts (e.g., short term (S) or long term (L) impacts) have been reported and tallied. For more information, see
http://www.cpc.ncep.noaa.gov/products/predictions/tools/edb/droughtblends.php.
10 See U.S. Drought Monitor, http://www.drought.unl.edu/dm/monitor.html.
11 The National Weather Service Forecast Office, Lubbock, Texas,
http://www.weather.gov/climate/index.php?wfo=lub.
12 The National Weather Service Forecast Office, Peachtree City, GA, http://www.nws.noaa.gov/climate/index.php?
wfo=ffc.
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Drought Is Multifaceted
In the past, U.S. Drought Monitor maps have used an “A” to indicate that the primary physical
effects are agricultural (crops, pastures, and grasslands) and an “H” to indicate that the primary
impacts of drought are hydrological (to water supplies such as rivers, groundwater, and
reservoirs). When both effects are apparent, the letters are combined, appearing as “AH.” In the
newer versions of the maps, such as the one shown in Figure 1, the “A” and “H” are replaced
with an “S” and “L.” These are experimental designations, according to the National Drought
Mitigation Center, which produces the U.S. Drought Monitor maps.13 The “S” designation is
intended to indicate a combination of drought indices that reflect impacts that respond to
precipitation over several days up to a few months (short-term effects). These would include
impact to agriculture, topsoil moisture, unregulated streamflows, and aspects of wildfire danger.
The “L” designation approximates responses to precipitation over several months up to a few
years (long-term effects). These would include reservoir levels, groundwater, and lake levels.
Figure 1 shows that the region around Lubbock, TX, is designated as L, whereas the region
closest to Athens, GA, shows an SL, indicating a combination of short-term and long-term
effects.
The U.S. Drought Monitor maps also indicate the intensity of a drought, ranging from abnormally
dry (shown as D0 on the maps) to exceptional drought (shown as D4). How these conditions are
assessed and how drought is classified are discussed below.
Drought Classification
To assess and classify the intensity and type of drought, certain measures, or drought indices, are
typically used. Drought intensity, in turn, is the trigger for local, state, and federal responses that
can lead to the flow of billions of dollars in relief to drought-stricken regions.14 The classification
of drought intensity, such as that shown in Figure 1 for May 8, 2012, may depend on a single
indicator or several indicators, often combined with expert opinion from the academic, public,
and private sectors. The U.S. Drought Monitor uses five key indicators,15 together with expert
opinion, with indices to account for conditions in the West where snowpack is relatively
important, and with other indices used mainly during the growing season.16 The U.S. Drought
Monitor intensity scheme—D0 to D4—is used to depict broad-scale conditions but not
necessarily drought circumstances at the local scale. For example, the large regions depicted as
red in Figure 1 faced extreme to exceptional drought conditions in May 2012, but they may
contain local areas and individual communities that experienced less (or more) severe drought.17
13 The complete designations are referred to as experimental objective blends of drought indicators,
http://www.cpc.ncep.noaa.gov/products/predictions/tools/edb/droughtblends.php.
14 For example, the Palmer Drought Index has been widely used by the U.S. Department of Agriculture to determine
when to grant emergency drought assistance. See NDMC, http://drought.unl.edu/Planning/Monitoring/
ComparisonofIndicesIntro/PDSI.aspx.
15 The five key indicators include the Palmer Drought Index, the Climate Prediction Center soil moisture model, U.S.
Geological Survey weekly streamflow data, the Standardized Precipitation Index, and short- and long-term drought
indicator blends. For a discussion of drought indices, see NDMC, http://droughtmonitor.unl.edu/current.html.
16 U.S. Drought Monitor, http://www.drought.unl.edu/dm/classify.htm.
17 The “S” and “L” terms shown in Figure 1 give additional information on the nature of the drought in the affected
region. For more information on the reasoning behind the classification schemes, see http://droughtmonitor.unl.edu/
classify.htm.
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Recent Examples: Texas, California, and Upper Colorado River
Basin
Drought in Texas—2011 and 2012
In early May of 2011 over 80% of Texas was experiencing extreme drought, and nearly 50% of
the state was in exceptional drought, the most severe level of drought intensity published by the
National Drought Mitigation Center.18 The 2011 drought in Texas represented a dramatic shift
compared to the same time period in 2010, when less than 6% of the total land area in Texas was
experiencing drought conditions, with no exceptional drought conditions anywhere in the state.
(See Figure 2, comparing 2010, 2011, and 2012.) In May 2012 the eastern half of Texas had
recovered from extreme or exceptional conditions, which—as of May 8, 2012—were affecting
24% and 7% of the state, respectively.
Figure 2. Comparison of Drought Conditions in Texas in 2010, 2011, and 2012
Source: U.S. Drought Monitor, http://droughtmonitor.unl.edu/, Modified by CRS.
Drought conditions worsened in Texas through the beginning of October 2011, when 88% of the
state experienced exceptional drought conditions (and only 3% of the state was not classified as
extreme or exceptional drought).19 Drought conditions generally improved throughout the rest of
2011, but large portions of the state were still affected by extreme or exceptional drought until
18 U.S. Drought Monitor, http://droughtmonitor.unl.edu/dmtabs_archive.htm.
19 See the U.S. Drought Monitor, Texas, on October 4, 2011, http://droughtmonitor.unl.edu/archive.html.
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late winter and early spring of 2012, when the eastern portion of the state recovered to normal or
abnormally dry conditions (the least severe category) because of above-normal rainfall from
December 2011 through February 2012.20
Drought Conditions Affecting the Rio Grande Project in 2011 and 2012
The 2011 and 2012 drought conditions in Texas and the Southwest have affected the amount of water in the Rio
Grande river, which flows south through New Mexico to form the U.S. border between Texas and northern Mexico.
The U.S. Bureau of Reclamation’s Rio Grande Project, which furnishes irrigation water for approximately 178,000
acres in New Mexico and Texas, as wel as electric power, includes the Elephant Butte dam and reservoir and the
Caballo Dam and reservoir. Both dams and reservoirs are in New Mexico, and about 60% of the lands receiving
irrigation water are in New Mexico. Elephant Butte dam and reservoir provide year-round electric power generation
and water during the irrigation season. Water released from Elephant Butte during winter power generation is stored
downstream in the Caballo reservoir for irrigation use during the summer. About 40% of the lands receiving water
from the project are in Texas, and water is also provided for diversion to Mexico to irrigate about 25,000 acres in the
Juarez Valley. The timing of the water releases in 2012 for delivery to Mexico and their potential impacts on U.S.
regional interests (e.g., potential conveyance losses because releases for Mexico would not be timed with deliveries to
U.S. water districts) have raised some concerns among some U.S. stakeholders about how scarce regional water
resources are to be managed during these dry conditions. Mexican growers sought the surface water deliveries
because pumping problems had impaired their ability to start the agricultural season using groundwater.
Inflow to Elephant Butte reservoir in 2011 was less than 15% of the 30-year average for March through July and is
expected to be 23% for 2012. The 2011 drought exacerbated low flows into the reservoir; flows into the reservoir
have exceeded average runoff values only three times in the past 15 years (1997, 2005, and 2008). As a result, the
Elephant Butte reservoir was at 9.6% of the combined reservoir capacity of 2.23 million acre-feet in early September
2011. For April 2012, it was at 17.9% of capacity. Consequently, the average water allocation from the Rio Grande
Project in 2011 was approximately 43% (although water available to individual water districts varies). The 2012
allocation is projected to be 20.5%, due to cumulative low inflows in the reservoirs. In contrast, the average allocation
in 2009 was 100%.
Due to low water levels, water deliveries from the Rio Grande Project to the irrigation district in Texas (El Paso
County Water Improvement District No. 1) as wel as to the city of El Paso ended on September 10, 2011. Under a
full allocation, the water deliveries normally extend through mid- or late-October. Because of 2011 conditions, the
New Mexico portion of the project, operated by the Elephant Butte Irrigation District, stopped taking surface water
deliveries in mid-July 2011. Rio Grande Project water users were receiving a 20% al ocation of water supplies as of
April 1, 2012.
Sources: U.S. Bureau of Reclamation, Rio Grande Project, http://www.usbr.gov/projects/Project.jsp?proj_Name=
Rio+Grande+Project; Texas Agrilife Research Center at El Paso, “Drought Watch on the Rio Grande,” September 2,
2011, and May 1, 2012; email from Dionne Thompson, Chief, Congressional and Legislative Affairs, U.S. Bureau of
Reclamation, September 15, 2011; personal communication with Filiberto Cortez, Division Manager, El Paso Field
Office, U.S. Bureau of Reclamation, May 2, 2012; letter from Patrick R. Gordon, Texas Commissioner, Rio Grande
Compact Commission, to Edward Drusina, Commissioner, United States Section, International Boundary and Water
Commission, April 9, 2012.
According to Texas state climatologist John Nielsen-Gammon, 2011 may be the worst one-year
drought on record for Texas.21 Compounding the effects of abnormally low precipitation, the
June-August average temperature in Texas was approximately 2.5 degrees Fahrenheit greater than
any previous Texas summer since 1895 and 5 degrees Fahrenheit (F) greater than the long-term
average.22 The 2011 U.S. Drought Monitor showed that Texas had been experiencing both
20 “Climate Abyss: Weather and Climate Issues with John Nielsen-Gammon,” Texas Drought Update, March 23, 2012,
http://blog.chron.com/climateabyss/2012/03/texas-drought-update/.
21 Office of the Texas State Climatologist, “Texas Drought Officially the Worst Ever,” August 4, 2011,
http://tamunews.tamu.edu/2011/08/04/texas-drought-officially-the-worst-ever/.
22 John W. Nielsen-Gammon, The 2011 Texas Drought: A Briefing Packet for the Texas Legislature, October 31, 2011,
(continued...)
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hydrological and agricultural drought, indicating that the drought has caused deficiencies in water
supplies as well as deficiencies of water to crops, plants, and grasses.
The most severe Texas drought overall occurred from 1950 to 1957, and had substantial impacts
on water supplies across the state because it lasted over many years. Because of the longevity and
severity of the 1950s drought, municipal water supplies in Texas today are designed to withstand
a drought of similar magnitude, according to the state climatologist.23 It is difficult to predict
whether drought conditions in Texas will persist through 2012 and longer. Long-term
precipitation patterns in Texas are influenced by a configuration of sea surface temperatures
known as the Pacific Decadal Oscillation (PDO). According to the Texas state climatologist, the
current PDO configuration associated with relatively dry weather in Texas has been present since
1998.24 Similar conditions also prevailed from the 1940s through the 1960s, encompassing the
Texas drought of record (1950-1957).
The 2007-2009 California Drought and Outlook for 2012
The 2007-2009 California drought25 was complicated by decades of tension over water supply
deliveries for irrigation and M&I uses, and the preservation of water flows to protect threatened
and endangered species. Dry conditions that began in 2007 continued through the 2009 water
year (October 2008 through September 2009) and into the fall of 2009. According to the
California Department of Water Resources, the 2007-2009 drought was the 12th-driest three-year
period in California history since measurements began.26 Although hydrological conditions were
classified as below normal in 2010 and “wet” (well above average) in 2011, the 2012 water year
is projected to be “dry” (well below normal).27 Above-average reservoir storage at the end of
2011 will mitigate reductions to water users; even so, water deliveries to state and federal water
project contractors have been restricted for 2012.28
During the drought years, drought conditions changed in the state so that some parts of the state
experienced more intense drought than others at different times of the year. For example, spring
rains reduced the intensity of the drought in some areas—parts of the state classified as extreme
in January 2009 were classified as severe in the late spring of that year. Nearly all of California
was classified as abnormally dry or under drought conditions through the fall of 2009 until rain
and snow in the late fall and early winter of 2010 relieved drought conditions in parts of the state,
including the Sierra Nevada. On March 30, 2011, Governor Jerry Brown proclaimed that the
(...continued)
p. 29, http://climatexas.tamu.edu/files/2011_drought.pdf.
23 Office of the Texas State Climatologist, “Texas Drought Officially the Worst Ever,” August 4, 2011,
http://tamunews.tamu.edu/2011/08/04/texas-drought-officially-the-worst-ever/.
24 John W. Nielsen-Gammon, The 2011 Texas Drought: A Briefing Packet for the Texas Legislature, p. 41.
25 For more information about the hydrology and policy issues involved in the 2007-2009 California drought, see CRS
Report R40979, California Drought: Hydrological and Regulatory Water Supply Issues, by Betsy A. Cody, Peter
Folger, and Cynthia Brougher.
26 California Department of Water Resources, California’s Drought of 2007-2009—An Overview, September 2010,
http://www.water.ca.gov/waterconditions/drought/docs/DroughtReport2010.pdf.
27 For information on water year classifications and water allocations to federal water contractors in California, see
http://www.usbr.gov/mp/PA/water/.
28 Ibid.
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drought was over.29 Most of California remained drought-free from spring 2010 through
December 2011—although the winter precipitation in 2011 was abnormally low. The 2012
Drought Monitor shows moderate drought conditions for most of California’s Central Valley from
January 2012 through April 2012.
California’s dry conditions from 2007 through 2009 exacerbated an already tight water supply,
where federal and state water deliveries had been reduced in response to a court order to prevent
extinction of the Delta smelt.30 Governor Arnold Schwarzenegger’s decision to declare drought in
2008 reflected the meteorological constraints on water supply together with court-imposed
restrictions on water supplies to protect endangered species, and long-standing restrictions to
protect water quality in the Delta. This combination of factors underscores why drought is
complex and not always simply a result of dry conditions.
Similar factors are still in play today. Water deliveries from state and federal water projects for
2012 are restricted due to legal actions to protect threatened and endangered species, water
quality requirements, and hydrological factors. (For more information on project water deliveries,
see CRS Report R40979, California Drought: Hydrological and Regulatory Water Supply Issues ,
by Betsy A. Cody, Peter Folger, and Cynthia Brougher
The 2012 Conditions in the Upper Colorado River Basin
Spanning parts of Arizona, California, Colorado, New Mexico, Nevada, Utah, and Wyoming, the
Colorado River basin is a critical water supply for the West and portions of northwestern Mexico.
Based on inflows observed over the last century, the river is over-allocated, and some contend
that supply and demand imbalances are likely to increase in the future.31 Drought in part of the
basin, particularly the upper basin, which is the source of most of the river’s flow, exacerbates
tensions over the sharing of the resource and results in difficult tradeoffs among the multiple uses
of water (e.g., municipal, agricultural, hydropower, energy, recreation, and ecosystem and species
demands). How water resources are allocated among these uses within a state is largely
determined by state water law, compliance with federal and state laws (including environmental
and resource management laws and regulations), and court decisions.
According to the U.S. Drought Monitor, severe drought continued through April 2012 in the
Upper Colorado River basin.32 Although 2011 was a wet water year, upper basin snowpack over
the 2011-2012 winter was low,33 and the snow melted early in the runoff season—one month
earlier than normal due to high temperatures in March and April.34 This early runoff, combined
29 Office of Governor Edmund G. Brown, Jr., “A Proclamation by the Governor of the State of California—Drought,”
http://gov.ca.gov/news.php?id=16997.
30 The Delta smelt is a species of fish. Natural Resources Defense Council v. Kempthorne, No. 1:05-cv-1207 OWW
GSA (E.D. Cal., December 14, 2007).
31 Bureau of Reclamation, U.S. Department of the Interior, Colorado River Basin Water Supply and Demand Study,
Phase 4: Development and Evaluation of Opportunities for Balancing Water Supply and Demand, November 2011,
http://www.usbr.gov/lc/region/programs/crbstudy/OptionsSubmittalReport.pdf.
32 National Weather Service, Drought Information Statement—Denver/Boulder, CO, May 3, 2012,
http://www.srh.noaa.gov/productview.php?pil=DGTBOU.
33 Natural Resources Conservation Service, U.S. Department of Agriculture, Westwide Snotel Current Snow Water
Equivalent (SWE) % of Normal, May 1, 2012, http://ccc.atmos.colostate.edu/pdfs/NIDIS_01_May_2012.pdf.
34 Letter from Water Resources Group, Bureau of Reclamation to All Colorado River Annual Operation Plan (AOP)
Recipients, April 24-Month Study, April 10, 2012, http://www.usbr.gov/uc/water/crsp/studies/24Month_04.pdf.
(continued...)
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with high reservoir levels carried over from 2011, produced a somewhat paradoxical situation of
combined storage in upper basin reservoirs of 127% of average in April 2012,35 while inflows to
the reservoirs are projected to be well below normal. The worries over future conditions are
derived from the exceptionally low streamflows projected for the upper basin36 because of the
poor snowpack; low streamflows mean less inflow into reservoirs over the late spring and
summer season.37 Low water availability in the Upper Colorado basin has effects beyond the
basin boundaries. For example, Colorado River water is transported from Colorado’s Western
Slope to the state’s Front Range; this water represents a significant contribution to the water
available for agricultural and municipal uses in many eastern Colorado counties.
What Causes Drought in the United States?
The immediate cause of drought is:
the predominant sinking motion of air (subsidence) that results in compressional warming or high
pressure, which inhibits cloud formation and results in lower relative humidity and less
precipitation. Regions under the influence of semi permanent high pressure during all or a major
portion of the year are usually deserts, such as the Sahara and Kalahari deserts of Africa and the
Gobi Desert of Asia.38
Prolonged droughts occur when these atmospheric conditions persist for months or years over a
certain region that typically does not experience such conditions for a prolonged period.39
Predicting drought is difficult because the ability to forecast surface temperature and precipitation
depends on a number of key variables, such as air-sea interactions, topography, soil moisture,
land surface processes, and other weather system dynamics.40 Scientists seek to understand how
all these variables interact and to further the ability to predict sustained and severe droughts
beyond a season or two in advance, which is the limit of drought forecasting abilities today.
In the tropics, a major portion of the atmospheric variability over months or years seems to be
associated with variations in sea surface temperatures (SSTs). Since the mid- to late 1990s,
scientists have increasingly linked drought in the United States to SSTs in the tropical Pacific
Ocean. Cooler than average SSTs in the eastern tropical Pacific region—“la Niña-like”
conditions—have been shown to be correlated with persistently strong drought conditions over
parts of the country, particularly the West.41 A number of recent studies have made the connection
(...continued)
Hereafter Water Resources Group, April 10, 2012.
35 Ibid. High inflows in spring and summer of 2011 improved storage levels at basin reservoirs; for instance, Lake
Powell increased its storage from 53% in 2010 to 64% in 2011.
36 Natural Resources Conservation Service, U.S. Department of Agriculture, Spring and Summer Streamflow Forecasts
as of May 1, 2012, http://www.wcc.nrcs.usda.gov/ftpref/support/water/westwide/streamflow/wy2012/strm1205.gif.
37 Water Resources Group, April 10, 2012.
38 See NDMC, at http://drought.unl.edu/DroughtBasics/PredictingDrought.aspx.
39 Ibid.
40 Ibid.
41 Cook et al., 2007.
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between cooler SSTs in the eastern Pacific and the 1998-2004 western drought,42 three
widespread and persistent droughts of the late 19th century,43 and past North American
“megadroughts” that occurred between approximately 900 and 1300 A.D.44 The precolonial
megadroughts apparently lasted longer and were more extreme than any U.S. droughts since
1850, when instrumental records began. Some modeling studies suggest that within a few decades
the western United States may again face higher base levels of dryness, or aridity, akin to the 900-
1300 A.D. period.45
Although the relationship between cooler than normal eastern tropical Pacific SSTs (La Niña-like
conditions) and drought is becoming more firmly established, meteorological drought is probably
never the result of a single cause. Climate is inherently variable, and accurately predicting
drought for one region in the United States for more than a few months or seasons in advance is
not yet possible because so many factors influence regional drought. What is emerging from the
scientific study of drought is an improved understanding of global linkages—called
teleconnections by scientists—between interacting weather systems, such as the El Niño-
Southern Oscillation, or ENSO. (See box for a description of ENSO.) For example, some
scientists link La Niña conditions between 1998 and 2002 with the occurrence of near-
simultaneous drought in the southern United States, Southern Europe, and Southwest Asia.46
El Niño-Southern Oscillation (ENSO)
Under normal conditions, the trade winds blow toward the west in the tropical Pacific Ocean, piling up the warm
surface waters so that the ocean surface off Indonesia is one-half meter higher than the ocean off Ecuador. As a
result, deep and cold water flows up to the surface (upwelling) off the west coast of South America. The upwelling
waters are 8 degrees Celsius (14.4 degrees Fahrenheit) cooler than waters in the western Pacific. During El Niño, the
trade winds relax, upwelling off South America weakens, and sea surface temperatures rise. The El Niño events occur
irregularly at intervals of 2-7 years, and typically last 12-18 months. These events often occur with changes in the
Southern Oscillation, a see-saw of atmospheric pressure measured at sea level between the western Pacific and Indian
Ocean, and the eastern Pacific. Under normal conditions, atmospheric pressure at sea level is high in the eastern
Pacific, and low in the western Pacific and Indian Oceans. As implied by its name, the atmospheric pressure oscillates,
or see-saws, between east and west; and during El Niño the atmospheric pressure builds up to abnormal y high levels
in the western tropical Pacific and Indian Oceans—the El Niño-Southern Oscillation, or ENSO. During a La Niña, the
situation is reversed: Abnormally high pressure builds up over the eastern Pacific, the trade winds are abnormally
strong, and cooler-than-normal sea surface temperatures occur off tropical South America. Scientists use the terms
ENSO or ENSO cycle to include the full range of variability observed, including both El Niño and La Niña events.
Source: Tropical Ocean Atmosphere Project, Pacific Marine Environmental Laboratory, at
http://www.pmel.noaa.gov/tao/proj_over/ensodefs.html.
42 Hoerling, Martin and Arun Kumar, “The perfect ocean for drought,” Science, vol. 299 (January 31, 2003), pp. 691-
694. Hereafter referred to as Hoerling and Kumar, 2003.
43 Herweiger, Celine, Richard Seager, and Edward Cook, “North American droughts of the mid to late nineteenth
century: a history, simulation and implication for Mediaeval drought,” The Holocene, vol. 15, no. 2 (January 31, 2006),
pp. 159-171. Hereafter referred to as Herweiger et al., 2006.
44 Cook et al., 2007.
45 Richard Seager et al., “Model projections of an imminent transition to a more arid climate in southwestern North
America,” Science, vol. 316 (May 25, 2007): pp. 1181-1184.
46 Hoerling and Kumar, 2003.
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Prehistorical and Historical Droughts in the United States
Some scientists refer to severe drought as “the greatest recurring natural disaster to strike North
America.”47 That claim stems from a reconstruction of drought conditions that extends back over
1,000 years, based on observations, historical and instrumental records where available, and on
tree-ring records or other proxies in the absence of direct measurements.48 What these
reconstructions illustrate is that the coterminous United States has experienced periods of severe
and long-lasting drought in the western states and also in the more humid East and Mississippi
Valley. The drought reconstructions from tree rings document that severe multidecadal drought
occurred in the American Southwest during the 13th century, which anthropologists and
archeologists suspect profoundly affected Pueblo society. Tree ring drought reconstructions also
document severe drought during the 14th, 15th, and 16th centuries in the central and lower
Mississippi Valley, possibly contributing to the disintegration of societies in that region.49
More recently, a combination of tree ring reconstructions and other proxy data, historical
accounts, and some early instrumental records identify three periods of severe drought in the 19th
century: 1856-1865 (the “Civil War drought”), 1870-1877, and 1890-1896.50 The 1856-1865
drought, centered on the Great Plains and Southwest, was the most severe drought to strike the
region over the last two centuries, according to one study.51 The 1890-1896 drought coincided
with a period in U.S. history of federal encouragement of large-scale efforts to irrigate the
relatively arid western states under authority of the Carey Act.52 Congressional debate also
occurred over a much larger federal role in western states irrigation, which led to the Reclamation
Act of 1902.
In the 20th century, the 1930s “Dust Bowl” drought and the 1950s Southwest drought are
commonly cited as the two most severe multiyear droughts in the United States.53 (The 1987-
1989 drought was also widespread and severe, mainly affecting the Great Plains but also
instigating extensive western forest fires, including the widespread Yellowstone fire of 1988.)
According to several studies, however, the 19th and 20th century severe droughts occurred during a
regime of relatively less arid conditions compared to the average aridity in the American West
during the 900 to 1300 A.D. megadroughts. One study indicates that the drought record from 900
to 1300 A.D. shows similar variability—drought periods followed by wetter periods—compared
to today, but the average climate conditions were much drier and led to more severe droughts.54
47 Cook et al., 2007.
48 Proxies are indirect measurements typically used where direct measurements are unavailable. Tree rings can be used
as a proxy for measuring dryness and drought. Similarly, ice cores from glaciers and polar caps can be used as proxies
for measuring atmospheric temperatures and carbon dioxide concentrations from thousands of years ago.
49 Cook et al., 2007.
50 Herweiger et al., 2006.
51 Ibid.
52 The Carey Act, signed into law on August 18, 1894 (Chapter 301, Section 4, 28 Stat. 422), initially made available
up to 1 million acres of federal land in each state, provided that the state met several requirements for the eventual
development of water resources for reclamation. Some observers have suggested that the failure of the Carey Act to
foster irrigation projects in all the land made available, compounded in part by the 1890-1896 drought, led to the
Reclamation Act of 1902 and the emergence of the Bureau of Reclamation in the 20th century. (See Marc Reisner,
Cadillac Desert (New York, New York, Penguin Books, 1986)).
53 Fye, F., D.W. Stahle, and E.R. Cook, “Paleoclimate analogs to twentieth century moisture regimes across the United
States,” Bulletin of the American Meteorological Society, 2003, vol. 84, pp. 901-909.
54 For example, one report showed that 42% of the area studied in the American West was affected by drought during
(continued...)
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Responding to and Planning for Drought
Several recent droughts were severe enough to trigger federal responses. When a drought is
declared by the U.S. President or by a state governor for a locality or region of the United States,
it sets in motion a series of alerts, recommendations, activities, and possible restrictions at the
local, regional, or state level, depending on the drought length and severity. Ultimately, a multi-
year severe drought could initiate a federal response and transfer of federal dollars to the affected
area.
Before drought severity reaches a level triggering a federal response, many states take action. For
example, the governor of Alabama issued a drought declaration on March 21, 2008, placing the
10 northernmost counties under an emergency drought declaration level, in accordance with the
draft Alabama Drought Management Plan.55 The emergency drought declaration level for
Alabama is its most extreme category of drought. According to Alabama’s plan, declaring drought
does not “automatically invoke a required response from the various categories of water users;”56
however, upon confirmation of a drought emergency, the governor’s office may issue “public
statements that a drought emergency exists, disaster declarations, and the appropriate
implementation of water conservation and drought emergency ordinances.”57 The National
Drought Mitigation Center posts online copies of drought management, mitigation, or response
plans for states and localities, nationwide.58 The California and Texas governors also have in
recent years issued state drought emergency declarations triggering state drought assistance.
Some states have also instituted water banks and water transfer mechanisms to deal with water
supply shortages (e.g., California, Idaho, and Texas).
Federal Aid
If the effects of a drought overwhelm state or local resources, the President, at the request of the
state governor, is authorized under the Stafford Act (42 U.S.C. 5121 et seq.) to issue major
disaster or emergency declarations that result in the distribution of federal aid to affected
parties.59 On October 20, 2007, the governor of Georgia requested a presidential drought disaster
declaration because of prolonged exceptional drought conditions existing in the northern third of
the state.60 However, no such presidential declaration occurred in response to the request from
Georgia. The last presidential drought or water shortage disaster declaration in the continental
United States was for New Jersey in 1980. More recent drought declarations have been issued for
U.S. territories in the Pacific.
(...continued)
the years 900 to 1300, versus 30% between 1900 and 2003, a 29% reduction in the average area affected by drought
between the two periods. See Cook et al., 2007.
55 For more information, see http://www.adeca.alabama.gov/Office%20of%20Water%20Resources/
Document%20Library/20080321%20-%20DroughtAdvisoryMap_Final.pdf.
56 Alabama Drought Management Plan, p. 7.
57 Ibid., p. 8.
58 For more information, see http://drought.unl.edu/Planning/PlanningInfobyState.aspx.
59 For more information about the Stafford Act, see CRS Report RL33053, Federal Stafford Act Disaster Assistance:
Presidential Declarations, Eligible Activities, and Funding, by Francis X. McCarthy; and CRS Report R41981,
Congressional Primer on Major Disasters and Emergencies, by Francis X. McCarthy and Jared T. Brown.
60 See http://www.fema.gov/news/disasters.fema.
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More frequently, a state governor requests drought disaster assistance through the U.S. Secretary
of Agriculture, who can declare an agricultural disaster as a result of drought and make available
low-interest loans and other emergency assistance through various U.S. Department of
Agriculture (USDA) programs.61 For example, on January 4, 2012, USDA designated 40 counties
in Texas as primary natural disaster areas due to losses caused by drought, excessive heat, high
winds, and wildfires.62 During the 2011 drought, USDA designated 213 counties in Texas as
primary natural disaster areas on June 27, 2011, when 90% of the state was experiencing extreme
drought conditions.63 The U.S. Army Corps of Engineers and the U.S. Bureau of Reclamation
also have limited drought emergency authorities and funding (e.g., the Reclamation States
Emergency Drought Act, as amended, 43 U.S.C. 2211 et seq.).
Under current U.S. farm policy, financial losses caused by drought and other natural disasters are
mitigated primarily through the federal crop insurance program (administered by the U.S.
Department of Agriculture’s Risk Management Agency). From 2000 to 2011, the federal
contribution to the crop insurance program averaged about $4.6 billion per year, mostly in the
form of a premium subsidy and reimbursements to private insurance companies. Since the severe
drought of 1988 and until passage of the 2008 farm bill (P.L. 110-246) , Congress regularly made
supplemental financial assistance available to farmers and ranchers, primarily in the form of crop
disaster payments and emergency livestock assistance. Crop disaster payments, paid to any
producer who experienced a major crop loss caused by a natural disaster, totaled $22.34 billion
from FY1989 to FY2009. More recently, under the 2008 farm bill (P.L. 110-246), Congress
authorized a $3.8 billion trust fund to cover the cost of making agricultural disaster assistance
available on an ongoing basis over four years (FY2008-FY2011).64 Among the authorized
programs, the Livestock Forage Disaster Program (LFP) assists ranchers who graze livestock on
drought-affected pastureland or grazing land. As of early May 2012, payments under LFP totaled
more than $500 million for losses through September 2011.
Federal Facilities and Drought
Even absent federal drought disaster declarations, sustained hydrological drought can affect
operations of federally managed reservoirs, dams, locks, hydroelectric facilities, and other
components of the nation’s water infrastructure. As discussed above, the 2007-2008 Southeast
drought directly affected how the Corps manages its facilities in the ACF basin (see box on
“Federal Reservoir Operations During Southeast Droughts”). Similarly, drought conditions in
California from 2007 to 2009, coupled with declining fish species, resulted in operational changes
to Reclamation facilities, including significantly reduced water deliveries to Central Valley
61 For more information, see CRS Report RS21212, Agricultural Disaster Assistance, by Dennis A. Shields and Ralph
M. Chite. See also CRS Report RL34207, Crop Insurance and Disaster Assistance in the 2008 Farm Bill, by Ralph M.
Chite and Dennis A. Shields.
62 U.S. Department of Agriculture, Farm Service Agency News Release, January 4, 2012, http://www.fsa.usda.gov/
FSA/newsReleases?area=newsroom&subject=landing&topic=edn&newstype=ednewsrel&type=detail&item=
ed_20120104_rel_0003.html.
63 U.S. Department of Agriculture, Farm Service Agency News Release, June 27, 2011, http://www.fsa.usda.gov/FSA/
newsReleases?area=newsroom&subject=landing&topic=edn&newstype=ednewsrel&type=detail&item=
ed_20110628_rel_0061.html.
64 The causes of crop loss can vary dramatically from year to year, although drought is one of the most common, if not
the most common, cause of crop loss. See CRS Report RS21212, Agricultural Disaster Assistance, by Dennis A.
Shields and Ralph M. Chite, and CRS Report RL31095, Emergency Funding for Agriculture: A Brief History of
Supplemental Appropriations, FY1989-FY2012, by Ralph M. Chite for more information.
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Project contractors, as well as to California’s State Water Project (SWP) contractors.
Reclamation, whose facilities currently serve over 31 million people in the West and deliver a
total of nearly 30 million acre-feet of water65 annually, faces operational challenges because of
conflicts among its water users during drought in states it serves.66
Federal Reservoir Operations During Southeast Droughts
An example of hydrological drought was the 2007-2008 drought in the southeastern United States. A persistent
severe drought in the region, beginning with below-average rainfall in spring 2006, exacerbated an ongoing interstate
dispute involving Alabama, Florida, and Georgia over water sharing in the Apalachicola-Chattahoochee-Flint (ACF)
river system. During the drought, Atlanta’s municipal and industrial water users in the upper basin were concerned
over the potential loss of their principal water supply, Lake Lanier, a surface water reservoir behind a U.S. Army
Corps of Engineers operated dam. Their concern resulted from the decision by the Corps to draw down Lake Lanier
in the fall of 2007. The Corps drew down the reservoir to maintain minimum flows in the lower basin Apalachicola
River to support species protection, energy production (e.g., power plant cooling), and lower basin municipal
withdrawals.67
The ACF tri-state conflict continues into 2012, and drought conditions have returned to the basin. As of June 2012,
the Southeast was experiencing widespread drought, with extreme and exceptional drought in southern Georgia and
the northern Florida peninsula. (See Figure 1.) Streamflows in the basin in the spring of 2012 were in the lowest
quintile on record. Consequently, total inflows into the Corps’ ACF reservoirs were below 50% of normal from
January to May 2012. As a result, reservoir storage levels are below normal. In May 2012 the Corps shifted its ACF
operations to provide only minimum flows to meet water supply, water quality, and environmental needs, thus
attempting to store more in its reservoirs. This operation level does not support navigation and only minimal
hydropower demands.
During and following the 2007-2008 drought, additional actions at the state level to manage water demand during
droughts were used and considered. To what extent similar activities will be implemented or necessary again revives
the policy questions of what actions should be taken by whom and when in a shared basin in order to adapt to the
dry conditions.
Source: NOAA, National Weather Service, Southeast River Forecast Center, When Did the Drought Begin, a Focus on
the North Georgia and Atlanta Areas, Nov. 16, 2007; National Integrated Drought Information System, Southeast US Pilot
for Apalachicola-Flint-Chattahoochee River Basin, June 5, 2012; U.S. Army Corps of Engineers, Average Daily Inflow to Lakes
by Month, Mobile, AL, June 12, 2012, http://water.sam.usace.army.mil/loclsumm.htm.
Severe drought conditions in 2001 in the Klamath River basin, on the Oregon-California border,
exacerbated competition for scarce water resources among farmers, Indian tribes, commercial and
sport fishermen, other recreationists, federal wildlife refuge managers, environmental groups, and
state, local, and tribal governments. Reclamation’s decision in April 2001 to withhold water from
farmers for instream flows for three fish species listed as endangered or threatened under the
Endangered Species Act sparked congressional debate that continues today. The Klamath basin
65 One acre-foot is enough water to cover one acre of land one foot deep. An acre-foot is equivalent to 325,851 gallons.
For more information about federal water supply programs, see CRS Report RL30478, Federally Supported Water
Supply and Wastewater Treatment Programs, coordinated by Claudia Copeland and others.
66 Reclamation is a central player in water resource management in the West, and a devastating drought at the end of
the 19th century was probably one of the many factors that led to the 1902 Reclamation Act that launched the federal
reclamation effort and Reclamation itself. See Marc Reisner, Cadillac Desert (New York: Penguin, 1986), pp. 108-109.
Other research suggests that the failures of some late 19th century private irrigation projects, undertaken following
passage of the Carey Act (see footnote 52), may have occurred in part due to drought conditions.
67 For more information on the ACF 2007-2008 drought and tri-state conflict, see CRS Report RL34326, Apalachicola-
Chattahoochee-Flint (ACF) Drought: Federal Water Management Issues, coordinated by Nicole T. Carter; and CRS
Report RL34440, Apalachicola-Chattahoochee-Flint Drought: Species and Ecosystem Management, by M. Lynne
Corn, Kristina Alexander, and Eugene H. Buck.
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again experienced drought conditions in 2010 and again is experiencing a lower than average
water year for 2012. Project water flows to Klamath refuges were halted from December 2011
through March 2012. Dry conditions contributed to a cholera outbreak among migrating birds
during this time, resulting in the death of thousands of birds that visit the refuges. However, early
spring precipitation improved hydrological conditions such that Reclamation projects full
irrigation deliveries for 2012.68
The droughts in California, the Southeast, and the Klamath River basin underscore an underlying
difficulty of managing federal reservoirs to meet multipurpose water needs. In the future, the
United States might face severe and sustained periods of drought not experienced in the 20th
century. If so, disputes over federal infrastructure management like those in California, the ACF
basin, and Klamath River basin may increasingly determine short-term actions by Reclamation
and the Corps, and result in long-term consequences for congressional oversight and funding.
Drought Forecasts for the United States
Predicting the severity and duration of severe drought over a specific region of the country is not
yet possible more than a few months in advance because of the many factors that influence
drought. Nevertheless, some modeling studies suggest that a transition to a more arid average
climate in the American West, perhaps similar to conditions in precolonial North America, may
be underway.69 Some studies have suggested that human influences on climate, caused by
emissions of greenhouse gases, may be responsible for a drying trend.70 Whether future
greenhouse gas-driven warming can be linked to La Niña-like conditions, or other phenomena
related to the El Niño-Southern Oscillation, is unclear.
A likely consequence of higher temperatures in the West would be higher evapotranspiration,
reduced precipitation, and decreased spring runoff.71 These impacts would result from an
“acceleration” of the hydrologic cycle, due to increased warming of the atmosphere, which in turn
increases the amount of water held in the atmosphere.72 A possible consequence is more frequent,
and perhaps more severe, droughts and floods. However, these changes are likely not to occur
evenly across the United States. Observations of water-related changes over the last century
suggest that runoff and streamflow in the Colorado and Columbia River basins has been
decreasing, along with the amount of ice in mountain glaciers in the West, and the amount of
annual precipitation in the Southwest.73 Yet the understanding of hydrologic extremes, such as
drought, is confounded by other effects such as land cover changes, the operation of dams,
68 U.S. Bureau of Reclamation, Klamath Project 2012 Operations Plan, April 6, 2012, p. 5, http://www.usbr.gov/mp/
kbao/docs/summer_operations.pdf.
69 Richard Seager et al., “Model projections of an imminent transition to a more arid climate in southwestern North
America,” Science, vol. 316 (May 25, 2007), pp. 1181-1184.
70 Tim P. Barnett, et al., “Human-induced changes in the hydrology of the western United States,” Science, vol. 319
(February 22, 2008), pp. 1080-1082.
71 Research results are emerging, however, that suggest that local and regional patterns of precipitation may be variable,
and parts of a region or a state could receive higher precipitation than the current average, even if the overall trend over
the broader area is towards less precipitation. See K. T. Redmond, “Climate Change in the Western United States:
Projections and Observations,” Eos Trans. AGU, 90(52), Fall Meet. Suppl., Abstract U11D-02, 2009.
72 National Research Council, Committee on Hydrologic Science, Global Change and Extreme Hydrology: Testing
Conventional Wisdom, Washington, D.C., 2011, p. 3.
73 Ibid., p. 7.
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irrigation works, extraction of groundwater, and other engineered changes. Forecasting drought
conditions at the regional scale, for example for river basins or smaller, is difficult because
current climate models are less robust and have higher uncertainty at smaller scales.74 (For
example, see box below on the Colorado River’s Lake Mead.)
Even though forecasting drought at the regional scale is difficult, understanding potential changes
in long-term trends is important for water managers at all levels—federal, state, local, and tribal.
Water project operations and state water allocations are typically based on past long-term
hydrological trends; significant deviations from such trends may result in difficult challenges for
water managers and water users alike.75 An example of such a dilemma can be observed in the
Colorado River basin.
Colorado River’s Lake Mead
A 2008 study asserted that water storage in Lake Mead has a 50% probability by 2021 to “run dry” and a 10% chance
by 2014 to drop below levels needed to provide hydroelectric power under current climate conditions and without
changes to water allocation in the basin. This study raised awareness of the vulnerability of western water systems
but drew criticism that global climate models are insufficient to forecast climate change effects at the regional scale.
Some western water officials were especially critical of the report’s assertions. One explained that Reclamation and
other agencies had recently developed new criteria for the allocation of Colorado River water in times of shortages
(shortage criteria), including drought, and commented that the likelihood that Lake Mead would run dry was
“absurd.” The study was based on predictions of future warming in the West without increased precipitation.
In a 2009 follow-up study, the same authors acknowledged that the ability of the Colorado River system to mitigate
drought could be managed if the users found a way to reduce average deliveries, thereby maintaining water levels in
Lake Mead and Lake Powell at consistently higher elevations. Maintaining higher water levels would increase the
capacity of the Colorado River system to buffer itself against low precipitation years. Even so, the authors noted,
global climate models are in broad agreement that the southwestern United States is likely to become warmer and
more arid, especially in the Colorado River drainage basin. In addition, paleoclimate studies suggest that the 20th
century was the wettest or second-wettest century for at least 500 years and possibly over the past 1,200 years.
Notwithstanding climate change, the paleoclimate data suggest that average future precipitation in the Colorado River
basin is unlikely to match what hydrologists believe were relatively wet 20th-century levels.
Sources: Tim P. Barnett and David W. Pierce, “When Will Lake Mead Go Dry?” Water Resources Research, vol. 44
(March 29, 2008), p. W03201, DOI:10.1029/2007WR006704; Felicity Barringer, “Lake Mead could be within a few
years of going dry, study finds,” New York Times (Feb. 13, 2008); Jenny Dennis, “Stunned Scientists: ‘When Will Lake
Mead Go Dry?’” Rim Country Gazette (Feb. 28, 2008), quoting Larry Dozier, Central Arizona Project deputy general
manager; Timothy P. Barnett and David W. Pierce, “Sustainable Water Deliveries from the Colorado River in a
Changing Climate,” Proceedings of the National Academy of Sciences, vol. 106, no. 18 (May 6, 2009).
Conditions in the Colorado River basin over the last decade, including recent low reservoir levels
in Lake Mead and low flows in the Upper Basin, raise the issue of what is the baseline for
average hydrologic cycles now and in the future. The allocation of Colorado River water supplies
was agreed upon by lower and upper basin states in the early part of the 20th century based on
hydrologic data from what scientists now know was a relatively wet period in the history of the
Colorado River basin.76 If long-term reduced runoff predictions for the basin are borne out (see
74 Ibid., p. 9.
75 P.C.D. Milly et al., “Stationarity Is Dead: Whither Water Management?,” Science, vol. 319 (February 4, 2008), p.
574.
76 The Colorado River basin is somewhat unusual in that the Secretary of the Interior acts as water “master” for the
river, and apportionment of water supplies among the basin states is done in accordance with the Colorado River
Compact and a body of law known as the “Law of the River.” For more information on the Law of the River, see
(continued...)
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box above on Colorado River’s Lake Mead), then water allocation policies for regions like the
Colorado River basin may need to be revisited.77 In the meantime, Colorado River basin states
have negotiated “shortage criteria” and “interim guidelines” for managing Colorado River water
supplies during times of shortages.78
Policy Challenges
Severe drought can exacerbate water competition, cause significant economic harm, and affect
nearly all areas of the country. Nonetheless, several key factors make comprehensive drought
policy at the national level a challenge, including:
• the “creeping” nature of drought;
• split federal and non-federal drought response and management responsibilities;
• a patchwork of federal programs and oversight with little coordination; and
• differences in regional conditions and drought risk in terms of the drought
hazard, vulnerability, and potential consequences.
Drought conditions often develop slowly and are not easily identified initially. Consequently,
drought declarations are made well after onset—typically once impacts are felt. This situation
makes it difficult to mitigate or prevent drought impacts. Further, even though drought generally
is continuously occurring somewhere in the United States, the unpredictability of its location,
duration, and severity complicates preparation for implementation of responses.
When severe meteorological drought affects a region, the supply of available water often shrinks
before use is reduced. Adjusting down the use of water as drought persists and supplies shrink can
be difficult. Actually, droughts can increase demand on water supplies (e.g., lower soil moisture
results in increased demand for irrigation and landscape watering). The flexibility of existing
water access and use arrangements limit the scope and speed of some drought responses. Federal,
state, and local authorities make water resource decisions within the context of multiple and often
conflicting laws and objectives, competing legal decisions, and entrenched institutional
mechanisms, including century-old water rights and long-standing contractual obligations (i.e.,
long-term water delivery and power contracts). Typically, how access to and competition for
water is managed (e.g., permitting of water withdrawals) and how reductions in water supply are
managed (e.g., shared reductions under a riparian system of water rights versus reductions based
on the priority in time of a water right) is determined by state law and at times through interstate
compacts. Additionally, state and local laws can determine how easily water can be transferred
(...continued)
http://www.usbr.gov/lc/region/g1000/lawofrvr.html.
77 Tim P. Barnett and David W. Pierce, “When Will Lake Mead Go Dry?” Water Resources Research, vol. 44 (March
29, 2008), p. W03201, DOI:10.1029/2007WR006704. Reservoir storage in the Colorado River basin has increased by
more than 8 million acre-feet since 2005. As of April 3, 2012, reservoir storage in the basin was nearly 63% of
capacity. Hydropower production has continued under 2007 “interim guidelines” for managing water shortages in the
Lower Colorado River basin.
78 For more information on 2012 operations, see http://www.usbr.gov/uc/water/crsp/studies/24Month_03.pdf, accessed
May 2, 2012. CRS has not determined to what degree recent scenarios are similar to those considered in studies
supporting the new shortage criteria for Colorado River water allocations under the Colorado River Compact.
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among users. These access, reduction, and transfer arrangements can significantly affect the
behavior, incentives, and opportunities available to water users during droughts. Fundamental
changes to the access, reduction, and transfer arrangements are largely outside of the realm of
federal action, and are largely determined by each state.
A mismatch between supply and demand during droughts underscores the responsibility of
stakeholders to anticipate the influence of drought and plan and act accordingly. The federal
government has several drought monitoring and response programs. While drought planning and
mitigation responsibilities lie largely at the state and local level, the federal government also
provides some drought planning assistance. Additionally, the federal government often provides
emergency funding for drought relief that is primarily aimed at easing the economic impacts. The
National Drought Commission and others have noted, however, that federal relief programs and
emergency funding provide little incentive for state and local planning and drought mitigation. A
policy issue particularly relevant to state and local decision makers is the role and types of
demand management tools to employ during a drought (e.g., lawn watering restrictions,
incentives to curtail irrigation during droughts, scarcity pricing). How a state distributes and
administers its waters among competing uses can affect what drought response tools are available
to it and to water users.
Australia’s Drought Experience: Water Markets as Drought Management
Australia experienced a historic drought from 1997 to 2009, known as the Millennium Drought. The drought tested a
preexisting multi-pronged national water reform initiative; one aspect of the reform was the development of water
markets. To develop water markets, the initiative had promoted reform of state law to clarify the property right
associated with a water right and facilitated the means to buy and sell perpetual water rights and short-term
allocations in basins that were ful y allocated. Water trade increased significantly during the later years of the drought
as allocations fell and markets matured. Allocations in some sub-basins during the worst of the drought reached as
low as 20% of a full allocation. While gross domestic production dropped by $2 billion-$3 billion in Australia’s most
significant agricultural basin during each of the worst drought years, the ability to trade water is estimated to have
reduced losses by roughly $1 billion during each drought year. The market’s ability to move scarce water to uses with
higher economic value is credited with assisting Australia’s rural economy to ride out the drought as well as it did by
getting more value per unit of water used. For example, some dairy farmers sold their water rights and purchased
fodder, rather than growing it themselves. Agricultural businesses increasingly used buying and selling in the water
market as a coping mechanism as the drought persisted. With water availability high in many basins since 2009,
market water prices have fal en, and rice and cotton production, which had declined during the drought, have picked
back up.
Water markets were not established in Australia without controversy and criticism. While not solely responsible,
water rights trading contributed to trends producing significant economic adjustment, particularly in rural agricultural
communities. Nonetheless, contemplating the consequences for Australia, especial y its agricultural communities and
businesses, of such a severe drought under a less flexible water rights regime has increased internal support for the
use and further improvement of water markets.
The broader water reform initiative produced some disappointments, as well as successes. The broader reform is
criticized for falling short of achieving ecologically sustainable levels of surface water withdrawals. Consequently, the
recent discourse about the next steps in Australian water policy has focused on how to establish sustainable levels of
withdrawals that can maintain ecosystems and support regional economies and how to cost-effectively secure the
water for the environment. Australia’s government uses the water markets to transition water out of existing uses
for use in meeting environmental flow goals; to date, the Australian government’s purchase of water rights for the
environment using the market has been less expensive than obtaining the water through infrastructure efficiency
improvements.
Source: National Water Commission (Australia), The Impacts of Water Trading in the Southern Murray-Darling Basin
Between 2006-07 and 2010-11, April 2012.
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A further challenge is lack of a cohesive national drought policy at the federal level, and lack of a
lead agency coordinating federal programs. Rather, several federal programs have been developed
over the years, often in response to specific droughts. Additionally, occasional widespread
economic effects have prompted creation of several federal relief programs. These programs are
overseen by different congressional committees. Whether this fragmentation results in
duplication, waste, and gaps, or whether it reflects the complexity of preparing and responding to
drought and the different responses needed by a wide range of stakeholders (e.g., irrigated
agriculture, dry land farming, municipal water utilities) is part of the debate about how to proceed
with cost-effective management of the nation’s drought risk and who bears the consequences of
drought. (See box above for an example of how water access and transfer arrangements played a
significant role in shaping Australia’s drought resilience and adaptation.)
Legislative Action
Congress has long recognized the lack of coordinated drought planning and mitigation activities
among federal agencies and the predominance of a crisis management approach to dealing with
drought. Over the last 15 years, legislative action has focused on the question of whether there is
a need for a national drought policy. For example, in 1998, Congress passed the National Drought
Policy Act (P.L. 105-199), which created a National Drought Policy Commission. In 2000, the
commission submitted to Congress a comprehensive report that included policy
recommendations. Congress has considered recommendations from the commission’s 2000
report; however, to date, it has enacted only one part of the recommendations (the National
Integrated Drought Information System, discussed below). Congress also considered, but did not
enact, legislation creating a National Drought Council during deliberations on the 2008 farm bill.
Both the commission findings and the proposed council are discussed below.
The National Drought Policy Act of 1998
In passing the National Drought Policy Act of 1998, Congress found that “at the Federal level,
even though historically there have been frequent, significant droughts of national consequences,
drought is addressed mainly through special legislation and ad hoc action rather than through a
systematic and permanent process as occurs with other natural disasters.”79 Further, Congress
found an increasing need at the federal level to emphasize preparedness, mitigation, and risk
management. Those findings are consistent with a recognition of the inevitability, albeit
unpredictability, of severe drought occurring.
The act created the National Drought Policy Commission, and required the commission to
conduct a study and submit a report to Congress on:
• what is needed to respond to drought emergencies;
• what federal laws and programs address drought;
• what are the pertinent state, tribal, and local laws; and
• how various needs, laws, and programs can be better integrated while
recognizing the primacy of states to control water through state law.
79 The National Drought Policy Act of 1998, P.L. 105-199 (42 U.S.C. 5121 note).
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In May 2000, the commission submitted its report,80 which included 29 specific recommendations
to achieve the goals of national drought policy, including the establishment of a National Drought
Council. (The Appendix of this report lists the five goals in the commission’s report.) As
background for its recommendations, the commission noted the patchwork nature of drought
programs, and that despite a major federal role in responding to drought, no single federal agency
leads or coordinates drought programs—instead, the federal role is more of “crisis
management.”81 Most of the specific recommendations were targeted at the President and federal
agencies, coupled with calls for Congress to fund drought-related activities in support of the
recommendations. An overarching recommendation was for Congress to pass a National Drought
Preparedness Act to implement the commission’s recommendations.
National Drought Preparedness Legislation and the 2008 Farm Bill
National Drought Preparedness Act bills were introduced in 2002 (107th Congress), 2003 (108th
Congress), and 2005 (109th Congress), but were not enacted. Similar stand-alone legislation was
introduced in the 110th Congress; however, the House-passed version of H.R. 2419, the Farm,
Nutrition, and Bioenergy Act of 2008 (also known as the 2008 farm bill), contained a section
creating a National Drought Council. This section of the 2008 farm bill would have charged the
council with creating a national drought policy action plan, which would have incorporated many
of the components recommended in the commission’s report; however, it was not included in the
conference agreement. Although the Senate version of H.R. 2419 did not contain a similar
section, the Senate bill authorized permanent disaster payments in hopes of precluding the need
for ad hoc disaster payments. The conference agreement on the 2008 farm bill (P.L. 110-246,
enacted June 18, 2008) included a new $3.8 billion trust fund to cover the cost of making
agricultural disaster assistance available on an ongoing basis over the following four years. The
assistance was available for disasters occurring on or before September 30, 2011, and has since
expired. The Senate Agriculture Committee version of the 2012 farm bill would authorize four of
the five disaster programs that received funding under the authority of the 2008 farm bill.82
National Integrated Drought Information System
Although Congress has not enacted comprehensive national drought preparedness legislation, it
acted on the second of five commission goals by passing the National Integrated Drought
Information System (NIDIS) Act of 2006 (P.L. 109-430). That goal called for enhanced
observation networks, monitoring, prediction, and information delivery of drought information.
P.L. 109-430 established NIDIS within the National Oceanic and Atmospheric Administration
(NOAA) to improve drought monitoring and forecasting abilities.83
80 Available at http://govinfo.library.unt.edu/drought/finalreport/fullreport/ndpcfullreportcovers/
ndpcreportcontents.htm.
81 Ibid., p. 1.
82 See CRS Report R42040, Farm Safety Net Proposals in the 112th Congress, by Dennis A. Shields and Randy
Schnepf.
83 NOAA allocated $12.1 million for NIDIS in FY2012. For more information about NIDIS, see
http://www.drought.gov.
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Conclusion
Drought is a natural hazard with potentially significant economic, social, and ecological
consequences. History suggests that severe and extended droughts are inevitable and part of
natural climate cycles. Drought has for centuries shaped the societies of North America and will
continue to do so into the future. Current understanding is that the physical conditions causing
drought in the United States are linked to sea surface temperatures in the tropical Pacific Ocean.
For example, the 2011 severe drought in Texas is thought to be linked to La Niña conditions in
the Pacific Ocean. Increasingly, studies are projecting the long-term role that droughts may play
in regional climate patterns. Nonetheless, available technology and science remains limited to
forecasting specific drought beyond a few months in advance for a region. The prospect of
extended droughts and more arid baseline conditions in parts of the United States represents a
challenge to existing public policy responses for preparing and responding to drought, and to
federal water resource projects in particular, because their construction was based largely on 19th-
and 20th-century hydrologic conditions.
Over time, Congress has created various drought programs, often in response to specific droughts
and authored by different committees. Crafting a broad drought policy that might encompass the
jurisdiction of many different congressional committees is often difficult. Additionally, although
many water allocation and other water management responsibilities largely lie at the state or local
level, localities and individuals often look to the federal government for relief when disasters
occur. This is similar to the situation for flood policy, and water policy in general, at the national
level. The National Drought Policy Commission recognized these patterns, and they underlie
many of its recommendations to Congress.84 The currently fragmented approach can be costly to
national taxpayers; however, it is not certain that increased federal investment (especially
vis-à-vis the potential for tailored local and state investment) in drought preparation, mitigation,
and improved coordination would produce more economically efficient outcomes.
The overall costs to the federal government as a result of extreme drought, apart from relief to the
agricultural sector, are difficult to assess. As discussed above, the operation of the nation’s
complex federal water infrastructure is affected by drought.
Congress may opt to revisit the commission’s recommendations and reevaluate whether current
federal practices could be supplemented with actions to coordinate, prepare for, and respond to
the unpredictable but inevitable occurrence of drought. Given the daunting task of managing
drought, Congress also may consider proposals to manage drought impacts, such as assisting
localities, industries, and agriculture with developing or augmenting water supplies. Congress
also may move to examine how the two major federal water management agencies, the Corps and
Reclamation, plan for and respond to severe drought and account for its impacts.
84 Infra, note 52.
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Appendix. Excerpt from the 2000 National Drought
Policy Commission Report to Congress
The following is an excerpt from the 2000 National Drought Policy Commission Report to
Congress: Preparing for Drought in the 21st Century—A Report of the National Drought Policy
Commission.
Policy Statement
• Favor preparedness over insurance, insurance over relief, and incentives over
regulation.
• Set research priorities based on the potential of the research results to reduce
drought impacts.
• Coordinate the delivery of federal services through cooperation and collaboration
with nonfederal entities.
Goals
Goal 1. Incorporate planning, implementation of plans and proactive mitigation measures, risk
management, resource stewardship, environmental considerations, and public education as the
key elements of effective national drought policy.
Goal 2. Improve collaboration among scientists and managers to enhance the effectiveness of
observation networks, monitoring, prediction, information delivery, and applied research and to
foster public understanding of and preparedness for drought.
Goal 3. Develop and incorporate comprehensive insurance and financial strategies into drought
preparedness plans.
Goal 4. Maintain a safety net of emergency relief that emphasizes sound stewardship of natural
resources and self-help.
Goal 5. Coordinate drought programs and response effectively, efficiently, and in a customer-
oriented manner.
Author Contact Information
Peter Folger
Nicole T. Carter
Specialist in Energy and Natural Resources Policy
Specialist in Natural Resources Policy
pfolger@crs.loc.gov, 7-1517
ncarter@crs.loc.gov, 7-0854
Betsy A. Cody
Specialist in Natural Resources Policy
bcody@crs.loc.gov, 7-7229
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