U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2013–5018

Prepared in cooperation with the Oklahoma Water Resources Board

Hydrologic Drought of Water Year 2011 Compared to Four 

Major Drought Periods of the 20th Century in Oklahoma
Cover:

North Canadian River near Calumet, Oklahoma, during drought conditions in July 2011 (photograph by J.A. Savoia, U.S. Geological Survey).
Hydrologic Drought of Water Year 2011 

Compared to Four Major Drought Periods of 

the 20th Century in Oklahoma

By Molly J. Shivers and William J. Andrews

Prepared in cooperation with the Oklahoma Water Resources Board

Scientific Investigations Report 2013–5018

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2013

This and other USGS information products are available at http://store.usgs.gov/

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U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Shivers, M.J., and Andrews, W.J., 2013, Hydrologic drought of water year 2011 compared to four major drought 

periods of the 20th century in Oklahoma: U.S. Geological Survey Scientific Investigations Report 2013-5018, 52 p., 

http://pubs.usgs.gov/sir/2013/5018/.
iii

Acknowledgments

The authors would like to thank several people for their contributions to the data collection and 

data analysis presented in this report. Darrell Townsend and Wynema Potter of the Grand River 

Dam Authority provided hydroelectric power generation data for Grand Lake, Lake Hudson, and 

the Salina project on Chimney Rock Lake. Ashley Corker of the Southwestern Power Administration provided hydroelectric power generation data for Fort Gibson Lake, Keystone Lake, Lake 

Eufaula, Lake Tenkiller, and Broken Bow Lake. Jennifer Rogers of the Oklahoma Municipal Power 

Authority provided hydroelectric power generation data for Kaw Lake. Gary McManus of the 

Oklahoma Climatological Survey provided customized maps of percentage of normal precipitation and departure from normal precipitation for water year 2011. U.S. Geological Survey 

personnel Jon Scott, S.J. Smith, and Joy Savoia provided low-flow and lake-level photographs 

taken in the late summer of 2011.
iv

Contents

Abstract...........................................................................................................................................................1

Introduction.....................................................................................................................................................1

Selected Consequences of the 2011 Drought..................................................................................2

Wildfires ........................................................................................................................................2

Required Water Conservation, Burn Bans, and States of Emergency ...............................2

Agriculture ....................................................................................................................................2

Tourism ..........................................................................................................................................3

Wildlife...........................................................................................................................................3

Purpose and Scope ..............................................................................................................................3

Progression of Drought........................................................................................................................3

Drought Sequence.......................................................................................................................3

Progression of Water Year 2011 Streamflow ..........................................................................3

Statewide Precipitation and Streamflow..........................................................................................4

Precipitation by Climate Division ..............................................................................................................14

Climate Division 1 Panhandle ...........................................................................................................14

Climate Division 2 North Central ......................................................................................................16

Climate Division 3 Northeast.............................................................................................................16

Climate Division 4 West Central .......................................................................................................16

Climate Division 5 Central..................................................................................................................16

Climate Division 6 East Central.........................................................................................................16

Climate Division 7 Southwest ...........................................................................................................16

Climate Division 8 South Central ......................................................................................................16

Climate Division 9 Southeast ............................................................................................................16

Streamflow of Long-Term Stations ...........................................................................................................16

Salt Fork Arkansas River at Tonkawa..............................................................................................20

Chikaskia River near Blackwell........................................................................................................20

Cimarron River near Waynoka..........................................................................................................20

Cimarron River near Ripley ...............................................................................................................20

Illinois River near Tahlequah.............................................................................................................20

Canadian River at Calvin....................................................................................................................26

North Canadian River near Wetumka..............................................................................................26

Salt Fork Red River at Mangum........................................................................................................26

Red River near Gainesville, Texas....................................................................................................26

Washita River near Dickson..............................................................................................................26

Blue River near Blue...........................................................................................................................26

Red River at Arthur City, Texas .........................................................................................................33

Effects of Low Streamflows .......................................................................................................................33

Conditions at Major Reservoirs........................................................................................................33

Hydroelectric Power Generation .....................................................................................................33

Groundwater Levels at Selected Long-term Stations ...........................................................................33

Summary........................................................................................................................................................41

References....................................................................................................................................................41

Appendixes 1–4. Photographs of Selected Sites at Normal/High-Flow Conditions

and Drought/Low-Flow Conditions, 2007–12..............................................................................47
v

Figures

1. Schematic diagram showing sequence of drought development .......................................4

2. Map showing monthly streamflow by percentile class, from U.S.

Geological Survey WaterWatch, October 2010 through September 2011 ..........................6

3. Barchart showing annual departure from the statewide long-term

median annual precipitation of 33.62 inches and a 5-year weighted

average for Oklahoma, water years 1925–2011.......................................................................8

4. Barchart showing annual departure from the statewide long-term median

annual runoff of 2.74 inches and a 5-year weighted average for Oklahoma,

water years 1925–2011...............................................................................................................11

5. Maps showing water resources regions and regional streamflow levels

in water year 2011.......................................................................................................................12

6. Graph showing percentage of streamflow-gaging stations with

below-normal streamflow from January 16, 2001, through

December 31, 2011, in Oklahoma .............................................................................................13

7. Map showing National Weather Service Climate Divisions in Oklahoma........................14

8. Maps showing percentage of normal precipitation A, and departure

from normal precipitation B, for Oklahoma, water year 2011..............................................15

9. Map showing selected long-term streamflow-gaging stations in

Oklahoma and appendix photograph locations.....................................................................17

 10. Barchart and graph showing streamflow data for Salt Fork Arkansas

River at Tonkawa, Oklahoma, water years 1942–2011. A, Annual departure

from long-term median annual streamflow. B, Comparison between

daily mean streamflow, water year 2011, and long-term daily mean streamflow ...........21

11. Barchart and graph showing streamflow data for Chikaskia River near Blackwell,

Oklahoma, water years 1937–2011. A, Annual departure from long-term

median annual streamflow. B, Comparison between daily mean streamflow,

water year 2011, and long-term daily mean streamflow......................................................22

12. Barchart and graph showing streamflow data for Cimarron River near Waynoka,

Oklahoma, water years 1938–2011. A, Annual departure from long-term median

annual streamflow. B, Comparison between daily mean streamflow,

water year 2011, and long-term daily mean streamflow......................................................23

13. Barchart and graph showing streamflow data for Cimarron River near Ripley, 

Oklahoma, water years 1940–2011. A, Annual departure from long-term median

annual streamflow. B, Comparison between daily mean streamflow,

water year 2011, and long-term daily mean streamflow .....................................................24

14. Barchart and graph showing streamflow data for Illinois River near Tahlequah, 

Oklahoma, water years 1936–2011. A, Annual departure from long-term median

annual streamflow. B, Comparison between daily mean streamflow, 

water year 2011, and long-term daily mean streamflow......................................................25

15. Barchart and graph showing streamflow data for Canadian River at Calvin,

Oklahoma, water years 1939–2011. A, Annual departure from long-term median

annual streamflow. B, Comparison between daily mean streamflow,

water year 2011, and long-term daily mean streamflow......................................................27

16. Barchart and graph showing streamflow data for North Canadian River

near Wetumka, Oklahoma, water years 1938–2011. A, Annual departure

from long-term median annual streamflow. B, Comparison between daily

mean streamflow, water year 2011, and long-term daily mean streamflow.....................28
vi

17. Barchart and graph showing streamflow data for Salt Fork Red River

at Mangum, Oklahoma, water years 1938–2011. A, Annual departure

from long-term median annual streamflow. B, Comparison between daily

mean streamflow, water year 2011, and long-term daily mean streamflow.....................29

18. Barchart and graph showing streamflow data for Red River near

Gainesville, Texas, water years 1937–2011. A, Annual departure from

long-term median annual streamflow. B, Comparison between daily mean

streamflow, water year 2011, and long-term daily mean streamflow ...............................30

19. Barchart and graph showing streamflow data for Washita River near Dickson, 

Oklahoma, water years 1929–2011. A, Annual departure from long-term median

annual streamflow. B, Comparison between daily mean streamflow,

water year 2011, and long-term daily mean streamflow......................................................31

20. Barchart and graph showing streamflow data for Blue River near Blue,

Oklahoma, water years 1937–2011. A, Annual departure from long-term

median annual streamflow. B, Comparison between daily mean streamflow,

water year 2011, and long-term daily mean streamflow......................................................32

21. Barchart and graph showing streamflow data for Red River at Arthur City,

Texas, water years 1945–2011. A, Annual departure from long-term median

annual streamflow. B, Comparison between daily mean streamflow, water

year 2011, and long-term daily mean streamflow .................................................................34

22. Map showing locations of selected major Oklahoma lakes and reservoirs

and percentage of conservation storage as of September 29, 2011..................................36

23. Graphs showing A, Daily-mean water levels, water year 2011 and

B, Long-term daily mean water levels and all water levels measured

in a groundwater well near Fittstown, Oklahoma, water years 1958–2012.......................38

24. Graphs showing A, Daily-mean water levels, water year 2011; long-term

daily mean water levels; and B, Continuously recorded water levels measured

in a groundwater well in Johnston County, Oklahoma, water years 2006–11..................39

25. Graphs showing A, Daily-mean water levels, water year 2011; B, Long-term

daily-mean water levels; and continuously recorded water levels measured

in a groundwater well near Texhoma, Oklahoma, water years 1956–2011.......................40

Tables

1. Summary of precipitation at National Weather Service Climate Divisions

in Oklahoma comparing the median of mean annual precipitation

during water years 1925–2006 with average annual precipitation during 

periods of previously documented hydrologic droughts and the recent

hydrologic drought period...........................................................................................................9

2. Summary of streamflow conditions at selected long-term

streamflow-gaging stations in Oklahoma comparing the median of

mean annual streamflow (measure of “normal” streamflow) with average

annual streamflow during periods of previously documented hydrologic

droughts and the recent hydrologic drought period.............................................................18

3. Storage in selected major Oklahoma lakes and reservoirs on

September 29, 2011, by National Weather Service Climate Division,

and comparison with April 14, 2011, storage .........................................................................35

4. Comparison of hydroelectric power generation at selected

Oklahoma hydroelectric plants between calendar years 2010 and 2011..........................37
vii

Conversion Factors

Inch/Pound to SI

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

square mile (mi2) 2.590 square kilometer (km2) 

acre 0.4047 hectare (ha)

Volume

acre-foot (acre-ft) 1,233 cubic meter (m3)

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second (m3/s)

Energy

gigawatt-hour (GWh) 3.6 x 1012 joule (J)

Temperature in degrees Fahrenheit (°F) may be converted to degrees Celsius (°C) as follows:

°C=(°F-32)×.56

Vertical coordinate information is referenced to the North American Vertical Datum of 1988 

(NAVD 88).

Horizontal coordinate information is referenced to the North American Datum of 1983 (NAD 83).

Altitude, as used in this report, refers to distance above the vertical datum.

Water year is the 12-month period October 1 through September 30, designated by the calendar 

year in which it ends

Hydrologic Drought of Water Year 2011 Compared to Four 

Major Drought Periods of the 20th Century in Oklahoma

By Molly J. Shivers and William J. Andrews

Abstract

Water year 2011 (October 1, 2010, through September 30, 

2011) was a year of hydrologic drought (based on streamflow) 

in Oklahoma and the second-driest year to date (based on 

precipitation) since 1925. Drought conditions worsened 

substantially in the summer, with the highest monthly average 

temperature record for all States being broken by Oklahoma in 

July (89.1 degrees Fahrenheit), June being the second hottest 

and August being the hottest on record for those months 

for the State since 1895. Drought conditions continued into 

the fall, with all of the State continuing to be in severe to 

exceptional drought through the end of September. In addition 

to effects on streamflow and reservoirs, the 2011 drought 

increased damage from wildfires, led to declarations of states 

of emergency, water-use restrictions, and outdoor burning 

bans; caused at least $2 billion of losses in the agricultural 

sector and higher prices for food and other agricultural 

products; caused losses of tourism and wildlife; reduced 

hydropower generation; and lowered groundwater levels in 

State aquifers.

The U.S. Geological Survey, in cooperation with the 

Oklahoma Water Resources Board, conducted an investigation 

to compare the severity of the 2011 drought with four previous 

major hydrologic drought periods during the 20th century – 

water years 1929–41, 1952–56, 1961–72, and 1976–81.

The period of water years 1925–2011 was selected as the 

period of record because few continuous record streamflowgaging stations existed before 1925, and gaps in time existed 

where no streamflow-gaging stations were operated before 

1925. In water year 2011, statewide annual precipitation was 

the 2d lowest, statewide annual streamflow was 16th lowest, 

and statewide annual runoff was 42d lowest of those 87 years 

of record. 

Annual area-averaged precipitation totals by the nine 

National Weather Service climate divisions from water year 

2011 were compared to those during four previous major 

hydrologic drought periods to show how precipitation deficits 

in Oklahoma varied by region. The nine climate divisions 

in Oklahoma had precipitation in water year 2011 ranging 

from 43 to 76 percent of normal annual precipitation, with 

the Northeast Climate Division having the closest to normal 

precipitation and the Southwest Climate Division having the 

greatest percentage of annual deficit. Based on precipitation 

amounts, water year 2011 ranked as the second driest of the 

1925–2011 period, being exceeded only in one year of the 

1952 to 1956 drought period.

Regional streamflow patterns for water year 2011 indicate 

that streamflow in the Arkansas-White-Red water resources 

region, which includes all of Oklahoma, was relatively large, 

being only the 26th lowest since 1930, primarily because 

of normal or above-normal streamflow in the northern part 

of the region. Twelve long-term streamflow-gaging stations 

with periods of record ranging from 67 to 83 years were 

selected to show how streamflow deficits varied by region 

in Oklahoma. Statewide, streamflow in water year 2011 was 

greater than streamflows measured in years during the drought 

periods of 1929–41, 1952–56, 1961–72, and 1976–81. The 

hydrologic drought worsened going from the northeast toward 

the southwest in Oklahoma, ranging from 140 percent (above 

normal streamflow) in the northeast, to 13 percent of normal 

streamflow in southwestern Oklahoma. The relatively low 

streamflow in 2011 resulted in 83.3 percent of the statewide 

conservation storage being available at the end of the water 

year in major reservoirs, similar to conservation storage in 

the preceding severe drought year of 2006. The ranking of 

streamflow as the 16th smallest for the 1925–2011 period, 

despite precipitation being ranked the 2d smallest, may have 

been caused, in part, by the relatively large streamflow in 

northeastern Oklahoma during water year 2011.

Introduction

Water year 2011 (October 1, 2010, through September 

30, 2011) was a year of hydrologic drought (based on 

streamflow) in Oklahoma, which had the second-driest year 

to date (based on precipitation) recorded since 1925. In 

Oklahoma, the drought was characterized by below-normal 
2 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

precipitation beginning in the fall and persisting through most 

of the remainder of the year, punctuated by some wet periods 

in eastern Oklahoma in the spring and summer. Drought 

conditions worsened substantially in the summer, breaking 

the all-time July statewide average temperature record for 

all States (89.1 degrees Fahrenheit [°F]). Statewide average 

temperatures in June were the second hottest on record for 

that month (83.5°F), and temperatures in August (87.7°F) 

were the hottest on record for that month in Oklahoma since 

1895 (Oklahoma Climatological Survey 2010a–c, 2011a–i). 

Drought conditions continued into the fall, with all of the 

State undergoing severe to exceptional drought through the 

end of September (U.S. Drought Monitor, 2011). This drought 

was caused primarily by weather patterns associated with La 

Niña conditions in the Pacific Ocean (National Oceanic and 

Atmospheric Administration (2011). To assist water-resource 

managers in evaluating the severity of the water year 2011 

hydrologic drought and in planning for future droughts, the 

U.S. Geological Survey, in cooperation with the Oklahoma 

Water Resources Board, conducted a study to summarize the 

water year 2011 hydrologic drought and compare it to the 

four previous major hydrologic drought periods of the 20th 

century: (1929–41, 1952–56, 1961–72, and 1976–81).

Hydrologic drought is associated with the effects of 

periods of below-normal precipitation on surface or subsurface 

water supplies. The severity of hydrologic drought is defined 

on a watershed or river-basin scale. Water in hydrologic 

storage systems of rivers and reservoirs commonly has 

multiple and competing purposes including flood control, 

irrigation, recreation, navigation, hydropower generation, 

and wildlife habitat. Competition for river and reservoir 

water escalates during droughts, and conflicts between 

water users can increase substantially (National Drought 

Mitigation Center, 2012a). Some of the consequences of the 

water year 2011 drought in Oklahoma are described in the 

following sections.

Selected Consequences of the 2011 Drought

Wildfires

Wildfires were a notable feature of the 2011 drought. 

Wildfires burned several hundred buildings and almost 

300,000 acres in Oklahoma in 2011 (Cable News Network, 

2011a and b; Dean and others, 2011; Olafson, 2011; Richter, 

2011; National Interagency Fire Center, 2012). Additional 

effects of wildfires included closure of nearby highways and 

evacuations of rural and urban residents in potential wildfire 

paths (Cable News Network, 2011b; Olafson, 2011;

Richter, 2011). 

Required Water Conservation, Burn Bans, and 

States of Emergency

Declining streamflow and lake levels and limited 

pumping infrastructure caused some Oklahoma watersuppliers to issue mandatory water-conservation measures 

during the summer of 2011. On June 29, the City of Goldsby 

banned all outdoor watering because of lowered production 

from a city well (KWTV, 2011a). On July 7, Logan County 

Rural Water District 1 banned lawn watering (KOTV, 2011). 

On July 9, Oklahoma City instituted a mandatory odd/even 

outdoor watering program based on dates and street addresses 

(Hertneky, 2011). Oklahoma City’s outdoor watering 

restrictions ended on August 11 after storms increased water 

levels in the city’s water-supply lakes (Overholser and Hefner) 

(KWTV, 2011b). As of September 7, 2011, 40 of 113 public 

water-supply systems surveyed had declared mandatory wateruse restrictions and 45 of those systems had asked customers 

to voluntarily restrict water use (Oklahoma Department of 

Environmental Quality, 2011).

In Oklahoma, burn bans which prohibit outdoor 

burning, but not cooking, can be issued by counties or the 

Governor. Burn bans were issued locally and by the Governor 

for counties across the State through the water year to 

prevent wildfires (Oklahoma Office of Secretary of State, 

2011a and b).

As of April 6, 2011, 47 of 77 counties in Oklahoma 

had issued burn bans to prevent wildfires (KJRH, 2011). 

On August 3, 2011, Governor Mary Fallin extended a 

45-county burn ban issued on July 15, 2011, to all 77 counties 

in Oklahoma (Hayes, 2011b). After precipitation in late 

September, Governor Fallin lifted the burn ban for 33 counties 

in the central and northern parts of Oklahoma (Associated 

Press, 2011).

On June 24, 2011, Oklahoma Lieutenant Governor 

Todd Lamb, at the request of Governor Fallin, declared a 

30-day state of emergency for 33 counties in northwestern, 

central, and southern parts of the State because of extreme 

or exceptional drought conditions and associated wildfires 

(Oklahoma Office of Secretary of State, 2011a). On September 

19, 2011, Governor Fallin amended the first declaration by 

issuing a 60-day state of emergency for all 77 counties in 

Oklahoma for exceptional drought conditions and numerous 

wildfires (Oklahoma Office of Secretary of State, 2011b).

Agriculture

In 2010, Oklahoma ranked first in production of rye, 

second in production of beef cattle, and third in production 

of winter wheat in the United States (Oklahoma Department 

of Agriculture, Food, and Forestry, 2011). The 2011 drought 

caused losses in crops and livestock in Oklahoma exceeding 

$1.6 billion (Hayes, 2011c). From April through September, 

soils in the State were rated as abnormally to severely dry and 

many cropland areas and pasture were being rated in the fair to 
Introduction 3

very poor range (Oklahoma Water Resources Board, 2011d–j). 

Li and Hiatt (2012) estimated from satellite imagery that crop 

and pasture biomass losses ranged from 1.2 to 2 tons per acre 

over much of the State. Compared to 2010, production of 

corn, grain sorghum, cotton, soybeans, sunflowers, and hay in 

2011 decreased 61, 87, 85, 71, 69, and 61 percent, respectively 

(National Agricultural Statistics Service, 2012a). Cotton 

acreage harvested in Oklahoma in 2011 was the smallest since 

1894 (Hayes, 2011d). Resulting high feed and hay prices and 

dry ponds forced many ranchers to sell cattle, thereby causing 

a reduction of about 12 percent of the State cattle inventory 

by the end of 2011, which contributed to record cattle prices 

by the end of the year and the smallest cattle inventories in 

the State since 1968 (Hayes, 2011d; National Agricultural 

Statistics Service, 2012b).

Tourism

Tourism, the third largest industry in Oklahoma, 

generates more than $6.1 billion annually in expenditures and 

employs nearly 76,000 people in the State (Oklahoma Tourism 

and Recreation Department, 2011). Much of the tourism in 

Oklahoma is associated with outdoor recreation on streams 

and lakes at State parks and elsewhere (Oklahoma Tourism 

and Recreation Department, 2011). Decreased streamflow 

and lake levels likely decreased receipts from water-related 

tourism in 2011 (Severson and Johnson, 2011). Warnings and 

beach closures enacted because of potentially toxic blooms 

of blue-green algae (Cyanophyta) in warm, stagnant water at 

many of the State’s largest reservoirs during the summer also 

decreased tourism (Murphy, 2011; Sewell, 2011; Lawrence, 

2012).

Wildlife

In addition to effects on humans and livestock, the 

drought conditions and wildfires of 2011 caused wildlife to 

have health problems and suffer from increased mortality. 

Deer in Texas and Oklahoma had lower rates of reproduction 

and survival, and fawns and deer were in poorer condition, 

as shown by smaller antler sizes (Medley, 2011a; Ray, 2011). 

Increased numbers of dehydrated baby squirrels prematurely 

left nests (Medley, 2011a). Fledgling avian wildlife such 

as hawks and kites died in above-normal numbers from 

hyperthermia and thirst (Medley, 2011a). The quail population 

across the State in 2011 was estimated to have decreased 25 

percent from the population surveyed in 2010 (Schoeling, 

2011). Freshwater mussels, including three threatened species, 

suffered increased mortality as streams and rivers dried up in 

southeastern Oklahoma (Vaughn and Atkinson, 2012). Lack 

of berries, acorns, and water caused by the drought forced 

black bears in eastern Oklahoma to scavenge at higher rates in 

suburbs and towns (Medley, 2011b).

Purpose and Scope

The purposes of this report are to describe and document 

the water year 2011 hydrologic drought in Oklahoma and 

effects of that drought and to compare the 2011 hydrologic 

drought to four previous major hydrologic drought periods of 

water years 1929–41, 1952–56, 1961–72, and 1976–81.

This report includes: (1) a definition of drought 

sequence, (2) a presentation of monthly nationwide steamflow 

displayed in U.S. Geological Survey WaterWatch graphics for 

water year 2011, and (3) a comparison of annual statewide 

total precipitation and statewide runoff (measurement of 

streamflows greater than base flows that are related to storm 

intensity) from water years 1925–2011 in Oklahoma with the 

four previous major hydrologic droughts of the 20th century 

highlighted. Annual area-averaged precipitation totals for 

water year 2011 for the nine National Weather Service Climate 

Divisions in Oklahoma are compared to precipitation during 

four previous major hydrologic droughts in the 20th century to 

show how precipitation deficits varied from normal by region. 

Mean annual streamflows during water year 2011 at 12 longterm streamflow-gaging stations are compared to streamflows 

during four previous major hydrologic droughts of the 20th 

century to show how streamflow deficits from the median 

varied by region. Effects of the 2011 drought are described, 

including: (1) increased wildfires, (2) increased mandates for 

water conservation and outdoor burning bans, (3) reduced 

crop yields and sell-offs of cattle herds, (4) reduced tourism, 

(5) increased mortality of wildlife, (6) reduced streamflow 

and conservation storage at major reservoirs in the State, (7) 

reduced hydroelectric power generation, and (8) decreased 

groundwater levels in major aquifers. 

Progression of Drought

Drought Sequence

Drought-sequence development is illustrated in figure 

1. A drought begins with precipitation deficiency, high 

temperatures and winds, and low humidity, collectively 

resulting in “meteorological” drought. As soil moisture 

is reduced and plants are stressed, “agricultural” drought 

occurs. If the drought continues for several seasons, 

streamflow is reduced to critical levels and “hydrologic” 

drought results (National Drought Mitigation Center, 2012a).

Progression of Water Year 2011 Streamflow

The WaterWatch Webpage of the U.S. Geological 

Survey maps monthly streamflow across the United States 

by percentile class (U.S. Geological Survey, 2012a). The 50th 

percentile represents the median monthly streamflow for 

the period of record, and normal streamflow is represented 

by the 25th to 75th percentiles of long-term median 
4 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

monthly streamflow. Figure 2 shows the ranges of streamflow 

in major basins in the United States, ranging from red 

tones for below long-term normal streamflow to blue tones 

for above long-term normal streamflow. Streamflow in 

Oklahoma was normal for most of the State from October 

through December 2010, but below-normal streamflow and 

much-below-normal streamflow increased from the southeast 

and northwest to include much of the State through the 

remainder of water year 2011 (fig. 2). The most widespread 

occurrence of much-below-normal streamflow during the 

water year was measured during July 2011, when muchbelow-normal streamflows were measured in about twothirds of the State (fig. 2).

Statewide Precipitation and Streamflow

Graphs of precipitation and estimated runoff of 

precipitation characterize the duration and severity 

of hydrologic drought by comparing annual statewide 

precipitation and runoff departures from long-term median 

annual precipitation values. Annual departures are shown 

as positive bars when values exceed the long-term median 

annual precipitation and as negative bars when values 

are less than the long-term median-annual precipitation. 

Departures that are consistently negative over several 

years provide a measure of drought duration or persistence, 

whereas the magnitudes of individual departures provide 

measures of severity.

Natural climate variability

Precipitation deficiency

(amount, intensity, timing)

Plant water stress

Reduced biomass and yield

Economic effects Social effects Environmental effects

Reduced runoff

Reduced infiltration and percolation

Reduced groundwater recharge

Reduced streamflow

Reduced inflow to reservoirs, lakes, and ponds

Reduced wetlands and wildlife habitats

Increased evaporation and transpiration

High temperature and winds

Low humidity

Greater sunshine

Less cloud cover

Soil water deficiency

Time duration

Meteorological

drought

Agricultural

drought

Hydrologic

drought

(Oklahoma Water Resources Board, 2007a; modified from National Drought Mitigation Center, 2012b)

Figure 1. Sequence of drought development.
Introduction 5

The period of water years 1925–2011 was selected as the 

period of record for long-term drought analysis. Before 1925 

few continuous record streamflow-gaging stations existed, 

and there were gaps when no streamflow gaging stations 

were operated in many parts of the State (U.S. Geological 

Survey, 2012b–c). Four previous major hydrologic drought 

periods of water years 1929–41, 1952–56, 1961–72, and 

1976–81 were identified from statewide runoff (Tortorelli 

and others, 1991; Tortorelli, 2008).

Figures 3 and 4 show annual statewide median 

precipitation and annual statewide median runoff, 

respectively, during water years 1925–2011. In figure 3, the 

statewide annual median precipitation for each water year of 

that period (National Climatic Data Center, 2012a) is plotted 

as departure from the long-term median annual precipitation 

for the period (blue line), and a 5-year weighted-average 

precipitation is plotted as a red line. Statewide, water year 

2011 was the second driest in the 87 years of record from 

1925–2011, based on precipitation (fig. 3, table 1). In figure 

4, the statewide annual median runoff for each water year 

of the period (U.S. Geological Survey, 2012d) is plotted as 

the departure from the long-term median annual runoff for 

the period (blue line), and a 5-year weighted-average runoff 

is plotted as a red line. In both figures 3 and 4, selected 

drought periods are indicated by differently colored bars. 

Statewide runoff in water year 2011 was the 42d smallest 

in the 87 years of record from 1925–2011 (fig. 4). In figures 

3 and 4, wetter years have bars above the median line and 

drier years have bars below the median line. The severity 

of drought conditions in water year 2011 can be compared 

to the four previous major hydrologic droughts by the depth 

of the bars representing dry years. The severity of the water 

year 2011 drought also can be compared to the four previous 

major hydrologic drought periods by the 5-year weighted 

average line.

Comparison of the 2011 drought with previous drought 

periods is useful for putting the extent and severity of the 

2011 drought in context. The hydrologic drought of water 

years 1929–41 was known as the “Dust Bowl” in the Great 

Plains and is documented in many references, including Hoyt 

(1936, 1938), Nace and Pluhowski (1965), Egan (2006), and 

National Drought Mitigation Center (2012b). The drought 

of the “Dust Bowl” years was particularly severe in western 

Oklahoma, with substantial runoff deficits of 2–3 inches 

per year and significant wind erosion over the entire State 

in 1936 (Nace and Pluhowski, 1965) (fig. 4). The 1929–41 

drought led to development of nationwide soil conservation 

measures (National Drought Mitigation Center, 2012b).

Despite the widely known effects of the “Dust Bowl” 

of the 1930s, the lesser-known hydrologic drought of water 

years 1952–56 was more severe. The drought of the mid1950s was the most widespread and the most severe for 

all regions of Oklahoma in terms of precipitation and for 

most regions in terms of runoff (Nace and Pluhowski, 1965; 

Tortorelli and others, 1991) (figs. 3 and 4).

The hydrologic drought of water years 1961–72 was as 

widespread and lasted longer than the drought of 1952–56 but 

generally was not as severe (Tortorelli and others, 1991) (figs. 

3 and 4). By 1972, many of the major reservoirs in Oklahoma 

built to augment water supplies during periodic droughts had 

been completed (Vance, 2007). The hydrologic drought of 

water years 1976–81 also was widespread, but was neither as 

severe nor as persistent as the previous three major drought 

periods (Tortorelli and others, 1991) (figs. 3 and 4).

Although Tortorelli (2008) described a drought period 

for water years 2002–2006, that period was neither as longlasting nor as severe as the four previous drought periods 

of the 20th century. In 2006, however, the drought was 

as severe as it had been in previous periods (figs. 3 and 

4). Record large rainfalls occurred during the summer of 

2007 in some parts of the state, with the subsequent years 

of 2008–10 having gradual decreases in above-normal 

precipitation and runoff (figs. 3 and 4). Water years 2006 

and 2011 were exceptionally dry years in an otherwise 

normal-to-wet period.

Based on runoff, which increases with more intensive 

precipitation, water year 2011 was the 42d driest in the 87 

years of record from 1925–2011 (fig. 4). Average statewide 

precipitation was the 2d lowest and average annual 

streamflow was the 16th lowest during the 1925–2011 study 

period (tables 1 and 2; figs. 3 and 4). Drought conditions 

in water year 2011 were severe, but drought duration or 

persistence of water year 2011 cannot yet be characterized, as 

of December 2012.

Regional streamflow patterns for water year 2011 

(fig. 5) indicate that streamflow in the Arkansas-White-Red 

water resources region, which includes all of Oklahoma, was 

the 26th driest since 1930 (U.S. Geological Survey, 2012e). 

The general pattern of greater-than-normal precipitation 

in the northern tier of States and less-than-normal 

precipitation in the southern tier of States is common to 

seasonal precipitation patterns in autumn, winter, and spring 

(National Weather Service, 2012). Normal or above-normal 

precipitation in northern parts of the Arkansas-WhiteRed water resources region contributed to near-normal 

streamflow in the region, despite much drier conditions in the 

southern part of the region. As an indicator of progression of 

the hydrologic drought during water year 2011, for some days 

in November 2010 almost 50 percent of long-term (having 

at least 30 years of record) streamflow-gaging stations had 

below-normal streamflow (fig. 6). In August 2011, near the 

peak of drought conditions (fig. 2), almost 90 percent of 

long-term streamflow-gaging stations in the state had belownormal streamflow (fig. 6).
6 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

U.S. Geological Survey (2012a)

October 2010 November 2010

December 2010 January 2011

February 2011 March 2011

EXPLANATION

Percentile classes

Low <10

Much

below

normal

10–24

Below

normal

25–75

Normal

76–90

Above

normal

>90

Much 

above

normal

High No data

Figure 2. Monthly streamflow by percentile class, from U.S. Geological Survey WaterWatch, October 2010 through September 2011.
Introduction 7

U.S. Geological Survey (2012a)

April 2011 May 2011

June 2011 July 2011

August 2011 September 2011

EXPLANATION

Percentile classes

Low <10

Much

below

normal

10–24

Below

normal

25–75

Normal

76–90

Above

normal

>90

Much 

above

normal

High No data

Figure 2. Monthly streamflow by percentile class, from U.S. Geological Survey WaterWatch, October 2010 through 

September 2011—Continued.
19

2

0 19

3

0 19

4

0 1950 19

6

0 1970 19

8

0 19

9

0

W

ater y

e

ar

-2

0

-16-12

-8-4

048

12162

0

2

4

2

8

Annual departure from median

annual precipitation, in inches per year

O

kla

h

o

m

a

state

wid

e

pre

cipitatio

n

19

2

5

–

2

011

dro

u

g

hts: 19

2

9

–

41 19

5

2

–

5

6 19

61–

7

2 19

7

6

–

81

H

y

drolo

gic

Above normal Below normal

A

n

nual d

e

parture

Lo

ng-term

m

e

dian an

nual precipitatio

n

5-y

ear w

eighte

d av

erage

EXPLANATION

Figure 3. Annual departure from the statewide long-term median annual precipitation of 33.62 inches and a 5-year weighted average for Oklahoma, 
Introduction 9

Table 1. Summary of precipitation at National Weather Service Climate Divisions in Oklahoma comparing the median of mean 

annual precipitation during water years 1925–2006 (measure of “normal” precipitation) with average annual precipitation during 

periods of previously documented hydrologic droughts (1929–41, 1952–56, 1961–72, 1976–81) and the recent (2011) hydrologic drought 

period.

[avg, average; rank, rank of driest year of drought period compared to period of record for water years 1925–2006; WY, water year; SW, statewide]

Climate 

division 

number

Climate 

division 

name

Long-term 

annual 

median

precipitation

(inches)

Hydrologic drought periods

1

1929–41

Lowest year/rank

1

1952–56 

Lowest year/rank

WY avg annual 

precipitation

(inches)

Long-term 

median

precipitation 

(percent)

WY avg annual 

precipitation

(inches)

Long-term 

median

precipitation 

(percent)

SW Statewide2 33.62 1936 6 1956 1

25.24 75 18.68 56

1 Panhandle3 19.84 1937 3 1956 2

12.24 62 11.34 57

2 North Central3 28.79 1936 8 1956 1

20.16 70 15.10 52

3 Northeast3 39.96 1939 13 1956 1

30.59 77 22.90 57

4 West Central3 26.39 1940 13 1952 3

20.14 76 15.98 61

5 Central3 34.33 1936 5 1956 2

24.03 70 19.74 58

6 East Central3 43.33 1936 4 1956 1

28.11 65 23.86 55

7 Southwest3 27.88 1939 8 1956 2

18.75 67 17.45 63

8 South Central3 37.47 1939 4 1956 1

24.19 65 16.46 44

9 Southeast3 48.13 1934 3 1956 1

30.86 64 25.10 52
10 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Table 1. Summary of precipitation at National Weather Service Climate Divisions in Oklahoma comparing the median of mean 

annual precipitation during water years 1925–2006 (measure of “normal” precipitation) with average annual precipitation during 

periods of previously documented hydrologic droughts (1929–41, 1952–56, 1961–72, 1976–81) and the recent (2011) hydrologic drought 

period.—Continued

[avg, average; rank, rank of driest year of drought period compared to period of record for water years 1925–2006; WY, water year; SW, statewide]

Climate 

division 

number

Hydrologic drought periods

1

1961–72 

Lowest year/rank

1

1976–81 

Lowest year/rank

2011

WY avg annual 

precipitation

(inches)

Rank longterm median

precipitation

(percent)

WY avg annual 

precipitation

(inches)

Long-term 

median

precipitation

(percent)

WY avg annual 

precipitation

(inches)

Long-term 

median

precipitation

(percent)

SW 1963 4 1978 11 2

24.60 73 27.11 81 20.05 60

1 1970 6 1976 38 1

13.05 66 17.58 89 11.09 56

2 1966 7 1976 21 4

20.15 70 23.24 81 17.96 62

3 1963 2 1981 21 11

24.81 62 32.89 82 30.17 76

4 1970 5 1976 34 1

18.00 68 22.23 84 12.65 48

5 1972 10 1976 12 1

25.08 73 25.41 74 19.59 57

6 1963 5 1980 8 2

28.24 65 30.30 70 26.08 60

7 1967 3 1980 33 1

17.46 63 23.40 84 12.05 43

8 1963 8 1978 13 2

25.15 67 27.78 74 18.86 50

9 1963 9 1978 5 4

35.02 73 31.95 66 31.51 65

1

Documented drought periods are modified from Tortorelli and others (1991). 

2

Ranks from Statewide Monthly Precipitation Totals, National Climatic Data Center (2012a).

3

Ranks from Climate Division Monthly Precipitation Totals, National Climatic Data Center (2012b).
Above normal Below normal

19

2

0 19

3

0 19

4

0 19

5

0 19

6

0 19

7

0 19

8

0 19

9

0

W

ater y

e

ar

-4-2

02468

10

Annual departure from median annual

runoff, in inches per year

O

kla

h

o

m

a

state

wid

e ru

n

off

19

2

5

–

2

011

EXPLANATION

A

n

nual d

e

parture

Lo

ng-term

m

e

dian an

nual run

off 2.74 inches

5-y

ear w

eighte

d av

erage

dro

u

g

hts: 19

2

9

–

41 19

5

2

–

5

6 19

61–

7

2 19

7

6

–

81

H

y

drolo

gic

Figure 4. Annual departure from the statewide long-term median annual runoff of 2.74 inches and a 5-year weighted average for Oklahoma, water y
12 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

The United States (including Puerto Rico) is divided into

21 large drainages, or water resources regions. These

hydrologic areas are based on surface topography and

contain either the drainage area of a major river, such as

the Columbia, the combined drainage areas of a series of

rivers, such as the Texas-Gulf region, which includes a

number of rivers draining into the Gulf of Mexico, or the

area of an island or island group. Water resources regions

provide a coherent, watershed-based framework for

depicting streamflow variations. 

Streamflow was at record high levels (ranking 1st in 82 years)

in the water resource regions of the Souris-Red-Rainy and

Mid-Atlantic regions. Above normal and much-above normal

streamflow occurred in all northeastern, northern, and western

regions, and in the Caribbean. In contrast, streamflow was at

record low levels (ranking 82nd in 82 years) in the South

Atlantic-Gulf, Texas-Gulf, and Alaska regions, respectively.

Below-normal and much-below normals were reported in the

Lower Mississippi and Rio Grande regions. 

U.S. Geological Survey (2012e)

EXPLANATION

Rank

82

Lowest

70–81

Much

below

normal

59–69

Below

normal

59–42

Normal

9–41

Above

normal

2–8

Much 

above

normal

Highest

Figure 5. Water resources regions and regional streamflow levels in water year 2011.
Introduction 13

2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012

Year

80

60

40

20

Percentage of streamflow-gaging stations with below-normal streamflow

0

EXPLANATION

The percent of streamflow-gaging stations with below-normal streamflow, plotted as the blue line in the above graph,

is calculated each day as the percent of streamflow-gaging stations having below-normal flow, where the lower

boundary for normal is the 25th percentile value of all historical streamflow values for all days of the year.

The percent of stations with below-normal streamflow is based only on streamflow-gaging stations in the state having

at least 30 years of record (U.S. Geological Survey, 2012f).

Figure 6. Percentage of streamflow-gaging stations with below-normal streamflow from January 16, 2001, through December 31, 2011, 

in Oklahoma.
14 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Precipitation by Climate Division

Oklahoma has nine National Weather Service Climate 

Divisions (fig. 7) for which monthly area-averaged 

precipitation data are available (National Climatic Data 

Center, 2012a). Those data were totaled for each water year 

from 1925–2011, indicating annual precipitation in Oklahoma 

on a regional basis.

Precipitation in the nine climate divisions of Oklahoma 

in water year 2011 was substantially less than the long-term 

median annual precipitation, with 2011 being ranked as the 

driest water year in Southwest, Central, West Central, and 

Panhandle Oklahoma Climate Divisions and as the 11th driest 

year in the Northeast Climate Division, with precipitation 

amounts ranging from 43 to 76 percent of long-term annual 

median amounts for the period 1925–2011 (table 1). Statewide 

precipitation in water year 2011 was the second smallest in 

the 87 years of record from 1925–2011, with 60 percent of 

the long-term median annual precipitation falling in the State. 

Only one year in the 1925–2011 period was drier—water 

year 1956, which had 56 percent of the long-term median 

precipitation.

Climatic variables in Oklahoma are, in part, measured by 

the Oklahoma Mesonet, a statewide network of 115 automated 

stations covering Oklahoma that records precipitation and 

other climatic data at 5-minute intervals. At least one Mesonet 

station is located in each of the 77 counties in Oklahoma. 

Oklahoma Mesonet climate data have been available since 

1994. In addition to data from the Mesonet, data from 

National Weather Service Stations (National Climatic Data 

Center, 2012a) were used for the period 1925–2011. Mesonet 

data use mean annual precipitation from calendar years 

1971–2000 instead of median annual precipitation from water 

years 1925–2011 for comparisons of long-term data. The 

1971–2000 period contained a significant wet period (fig. 3); 

therefore, data presented on the Mesonet Website (fig. 8A) 

indicated more severe precipitation deficits in 2011 than 

indicated in table 1 of this report. The departure from normal 

precipitation (fig. 8B) indicates the statewide distribution 

of precipitation deficits in water year 2011, as compared to 

the 1971–2000 period.

Climate Division 1 Panhandle

For Climate Division 1 Panhandle in far northwestern 

Oklahoma (fig. 7), water year 2011 was the driest in 87 years 

of record from 1925–2011, having received an average of 

11.09 in. of precipitation (table 1). That precipitation amount 

was 56 percent of the long-term median annual precipitation, a 

deficit of 8.75 in. (table 1).

1 2 3

4

5

6

7

8 9

CENTRAL

NORTHEAST

PANHANDLE

SOUTHWEST

SOUTHEAST

SOUTH

CENTRAL

NORTH CENTRAL

EAST

CENTRAL

WEST

CENTRAL

O K L AHO MA

Albers Equal Area Conic Projection

Climate Division number

and name

5

CENTRAL

EXPLANATION

Modified from Oklahoma Climatological Survey (2000)

0 50 100 200 MILES

0 100 200 KILOMETERS

Figure 7. National Weather Service Climate Divisions in Oklahoma.
Precipitation by Climate Division 15

Figure 8. Percentage of normal precipitation, A, and departure from normal precipitation, B, for Oklahoma, water year 2011.

Figure 8. Oklahoma (A) percent of normal rainfall, water year 2011, (B) departure from normal rainfall, water year 2011.

(G. McManus, Oklahoma Climatological Survey, written commun., 2012; “normal” rainfall is defined as mean annual precipitation from calendar

years 1971–2000 in this figure)

A

B
16 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Climate Division 2 North Central

For Climate Division 2 North Central in north-central 

Oklahoma (fig. 7), water year 2011 was the fourth driest 

in 87 years of record from 1925–2011, with 17.96 in. of 

precipitation falling, representing 62 percent of the long-term 

median annual precipitation, a deficit of 10.83 in. (table 1). 

Water year 1956 was the driest year recorded for Climate 

Division 2 North Central, with 15.10 in. of precipitation, 

52 percent of the long-term median annual precipitation, and a 

deficit of 13.69 in. (table 1).

Climate Division 3 Northeast

For Climate Division 3 Northeast in northeastern 

Oklahoma (fig. 7), water year 2011 was the 11th driest in 

87 years of record from 1925–2011, having received 30.17 in. 

of precipitation, 76 percent of the long-term median annual 

precipitation, and a deficit of 9.79 in. (table 1). Water year 1956 

was the driest year recorded for Climate Division 3 Northeast, 

having received 22.90 in. of precipitation, 57 percent of 

the long-term median annual precipitation, and a deficit of 

17.06 in. (table 1). 

Climate Division 4 West Central

For Climate Division 4 West Central in west-central 

Oklahoma (fig. 7), water year 2011 was the driest in 87 years 

of record from 1925–2011, having received an average of 

12.65 in. of precipitation (table 1). The precipitation amount 

for water year 2011 in Climate Division 4 West Central was 

48 percent of the long-term median annual precipitation, 

representing a deficit of 13.74 in. (table 1).

Climate Division 5 Central

For Climate Division 5 Central in central Oklahoma 

(fig. 7), water year 2011 was the driest in 87 years of record 

from 1925–2011, having received an average of 19.59 in. of 

precipitation. The precipitation amount for water year 2011 in 

Climate Division 5 Central was 57 percent of the long-term 

median annual precipitation, a deficit of 14.74 in. (table 1). 

Climate Division 6 East Central

For Climate Division 6 East Central in east-central 

Oklahoma (fig. 7), water year 2011 was the second driest in 

the 87 years of record from 1925–2011, having received an 

average of 26.08 in. of precipitation, 60 percent of the longterm median annual precipitation, and a deficit of 17.25 in. 

(table 1). Water year 1956 was the driest year recorded for 

Climate Division 6 East Central, having received 23.86 in. 

of precipitation, 55 percent of the long-term median annual 

precipitation, and a deficit of 19.47 in. (table 1).

Climate Division 7 Southwest

For Climate Division 7 Southwest in southwestern 

Oklahoma (fig. 7), water year 2011 was the driest in the 

87 years of record from 1925–2011, receiving an average of 

12.05 in. of precipitation. The precipitation amount for water 

year 2011 in Climate Division 7 Southwest was 43 percent 

of the long-term median annual precipitation, a deficit of 

15.83 in. (table 1). 

Climate Division 8 South Central

For Climate Division 8 South Central in south-central 

Oklahoma (fig. 7), water year 2011 was the second driest 

in the 87 years of record from 1925–2011, having received 

18.86 in. of precipitation, which was 50 percent of the longterm median annual precipitation, a deficit of 18.61 in. (table 

1). Water year 1956 was the driest year recorded for Climate 

Division 8 South Central, receiving an average of 16.46 in. of 

precipitation, which was 44 percent of the long-term median 

annual precipitation, a deficit of 21.01 in. (table 1).

Climate Division 9 Southeast

For Climate Division 9 Southeast in southeastern 

Oklahoma (fig. 7), water year 2011 was the fourth driest in the 

87 years of record from 1925–2011, receiving an average of 

31.51 in. of precipitation, which was 65 percent of the longterm median annual precipitation, a deficit of 16.62 in. (table 

1). Water year 1956 was the driest year recorded for Climate 

Division 9 Southeast, having received an average of 25.10 in. 

of precipitation, which was 52 percent of the long-term 

median annual precipitation, a deficit of 23.03 in. (table 1).

Streamflow of Long-Term Stations

Twelve long-term streamflow-gaging stations with 

periods of record ranging from 67 to 83 years were selected 

to show how streamflow deficits varied by region (fig. 9, 

table 2). Two graphs are presented for each long-term station 

(figs. 10–21). The first graph (A) for each station is similar 

to the statewide runoff graph in figure 4. The median annual 

streamflow (U.S. Geological Survey, 2012b) for each water 

year of the period of record is plotted as a departure from the 

long-term median annual streamflow (blue line), and a 5-year 

weighted-average streamflow is plotted as a red line (all A

graphs, figs. 10–21). Wetter-than-normal years plot above 

the median line and drier-than-normal years plot below the 

median line. Water year 2011 can be compared to dry years 

from the four previous major hydrologic droughts in the 20th 

century by comparing the magnitude of the deviations from 

the median value. The second graph on figures 10–21 

shows comparisons of daily mean streamflow from water 
102 ̊ 100 ̊ 98 ̊ 96 ̊

102 ̊ 100 ̊ 98 ̊ 96 ̊

36 ̊34 ̊

Red River nearGainesville, Texas 

Red RArthu

Blue Rivernear Blue 

WashitaRiver nearDickson 

Salt Fork Red

River at Mangum 

North CanadianRiver near Wetumka 

River

Canadian River

at Calvin 

CimarronRiver near Ripley 

Salt ForkArkansasRiver at Tonkawa 

Chikaskia Rivernear Blackwell 

CimarronRiver nearWaynoka 

Verdigris River 

Figure 9. Selected long-term streamflow-gaging stations in Oklahoma and appendix photograph locations.
18 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Table 2. Summary of streamflow conditions at selected long-term streamflow-gaging stations in Oklahoma comparing the median of 

mean annual streamflow (measure of “normal” streamflow) with average annual streamflow during periods of previously documented 

hydrologic droughts (1929–41, 1952–56, 1961–72, 1976–81) and the recent (2011) hydrologic drought period.

[mi2, square miles; N, nonregulated; R, regulated; WY, water year; ft3/s, cubic feet per second; rank, rank of driest year of drought period compared to period of 

record; avg, average; SW, statewide]

Site 

number

Station 

number Station name

Contributing 

drainage 

area

(mi2)

Type of 

record

(N/R)

Continuous 

period of 

record

(complete 

WY)

Years of

record

Long-term 

annual 

median

(ft3/s)

SW Statewide1 11925–2011 87

1 07151000 Salt Fork Arkansas River at Tonkawa, Okla. 4,520 R 1942–2011 70 812

2 07152000 Chikaskia River near Blackwell, Okla. 1,859 N 1937–2011 75 499

3 07158000 Cimarron River near Waynoka, Okla. 8,504 N 1938–2011 74 223

4 07161450 Cimarron River near Ripley, Okla.2 13,053 N 1940–2011 72 1,347

5 07196500 Illinois River near Tahlequah, Okla. 959 N 1936–2011 76 950

6 07231500 Canadian River at Calvin, Okla. 23,151 N,R 1939–42, 

1945–2011

71 1,439

7 07242000 North Canadian River near Wetumka, Okla. 9,391 R 1938–2011 74 692

8 07300500 Salt Fork Red River at Mangum, Okla. 1,357 N 1938–2011 74 67.7

9 07316000 Red River near Gainesville, Texas 24,846 N,R 1937–2011 75 2,508

10 07331000 Washita River near Dickson, Okla. 7,202 N,R 1929–2011 83 1,723

11 07332500 Blue River near Blue, Okla. 476 N 1937–2011 75 253

12 07335500 Red River at Arthur City, Texas 38,595 R 1945–2011 67 6,909
Streamflow of Long-Term Stations 19

Table 2. Summary of streamflow conditions at selected long-term streamflow-gaging stations in Oklahoma comparing the median of 

mean annual streamflow (measure of “normal” streamflow) with average annual streamflow during periods of previously documented 

hydrologic droughts (1929–41, 1952–56, 1961–72, 1976–81) and the recent (2011) hydrologic drought period.—Continued

[mi2, square miles; N, nonregulated; R, regulated; WY, water year; ft3/s, cubic feet per second; rank, rank of driest year of drought period compared to period of 

record; avg, average; SW, statewide]

Site 

number

Hydrologic drought periods

3

1929–41 

Lowest year/rank

3

1952–56

Lowest year/rank

 31961–72

Lowest year/rank

 31976–81

Lowest year/rank 2011

Avg 

annual 

flow

(ft3/s)

Long-term 

medianannual 

streamflow

(percent)

Avg 

annual 

flow

(ft3/s)

Long-term 

medianannual 

streamflow

(percent)

Avg 

annual 

flow

(ft3/s)

Long-term 

medianannual 

streamflow

(percent)

Avg 

annual 

flow

(ft3/s)

Long-term 

medianannual 

streamflow

(percent)

Avg 

annual 

flow

(ft3/s)

Rank longterm 

medianannual 

streamflow

(percent)

SW 1940 3 1956 1 1964 4 1981 12 16

1 NA 1954 1 1964 3 1981 14 4

95.5 12 137 17 280 34 147 18

2 41940 2 1954 1 1966 4 1981 8 5

76.6 15 71.0 14 97.6 20 152 30 102 20

3 41939 30 1956 6 1971 5 1977 21 1

174 78 53.6 24 46.7 21 134 60 31.9 14

4 41940 4 1953 1 1971 2 1981 12 5

307 23 235 17 294 22 455 34 312 23

5 41940 6 1954 1 1964 3 1981 5 63

279 29 193 20 239 25 275 29 1,333 140

6 41940 9 1956 7 1966 3 1981 1 4

478 33 393 27 217 15 184 13 237 16

7 41940 2 1956 1 1963 3 1981 5 9

157 23 156 23 166 24 178 26 215 31

8 41940 1 1952 5 1971 3 1981 6 2

12.3 18 17.5 26 12.5 18 22.7 34 12.4 18

9 41939 6 1953 3 1964 4 1983 13 1

1,010 40 651 26 654 26 1,274 51 315 13

10 41939 4 1956 6 1964 2 1981 8 1

391 23 440 26 340 20 495 29 316 18

11 41939 2 1956 1 1964 10 1980 5 4

42.9 17 30.8 12 114 45 77.7 31 69.8 28

12 NA 1952 10 1964 3 1980 4 2

4,182 61 2,754 40 2,953 43 2,008 29

1

Ranks from U.S. Geological Survey (2012a).

2

Includes streamflow record 1940–87 from nearby station 07161000, Cimarron River at Perkins, Okla.

3

Documented drought periods are modified from Tortorelli and others (1991).

4

Station records do not span entire drought period.
20 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

year 2011 (red line) (U.S. Geological Survey, 2012b) to the 

long-term daily mean streamflow (blue line) (U.S. Geological 

Survey, 2012b) and provides an indication of how the 

streamflow deficits changed seasonally during water year 

2011 compared to the period of record at that gage (all B

graphs, figs 10–21). Statewide, water year 2011 had averageannual streamflow that was the 16th smallest of the period 

1925–2011, more than was recorded during the drought 

periods of 1929–41, 1952–56, 1961–72, and 1976–81 (table 2). 

An average-annual streamflow ranking of only 16th smallest 

for this period, despite precipitation being ranked the 2d 

smallest, may be related to the relatively large streamflow in 

northeastern Oklahoma during water year 2011.

Salt Fork Arkansas River at Tonkawa

Salt Fork Arkansas River at Tonkawa, Okla. (station 

number 07151000) is a streamflow-gaging station in northcentral Oklahoma (fig 9). Water year 2011 was the fourth 

driest in the 70 years of record at the station for the period 

1942–2011, with 18 percent of long-term median annual 

streamflow being recorded (table 2). Water year 1954 was 

the driest year at the station, with 12 percent of long-term 

median annual streamflow being recorded. Zero streamflow 

was not recorded during water year 2011, similar to the 

drought year 2006 (Tortorelli, 2008), with some streamflow 

near the long-term daily mean streamflow being recorded 

in November, May, August, and September (fig. 10). The 

smallest daily mean streamflow during water year 2011 was 

4 cubic feet per second (ft3/s) recorded on September 13, 2011 

(fig. 10) (U.S. Geological Survey, 2012c).

Chikaskia River near Blackwell

Chikaskia River near Blackwell, Okla. (station number 

07152000) is a streamflow-gaging station in north-central 

Oklahoma (fig. 9). Water year 2011 was the fifth driest 

in the 75 years of record from 1937–2011 at that station, 

with 20 percent of long-term median annual streamflow 

being recorded (table 2). Water year 1954 was the driest 

year at the station, with 14 percent of long-term median 

annual streamflow being recorded. Zero streamflow was 

not recorded during water year 2011 at the station, similar 

to the drought year of 2006 (Tortorelli, 2008), with some 

above-median streamflow recorded in February, April, and 

mid-September (fig. 11). The smallest daily mean streamflow 

during water year 2011 was 1.5 ft3/s recorded on September 

6, 2011 (fig. 11) (U.S. Geological Survey, 2012c).

Cimarron River near Waynoka

Cimarron River near Waynoka, Okla. (station number 

07158000) is a streamflow-gaging station in northwestern 

Oklahoma (fig. 9). Water year 2011 was the driest in the 74 

years of record from 1938–2011, with 14 percent of the longterm median annual streamflow being recorded (table 2). 

During the drought of water year 2006, zero streamflow was 

recorded at this station only during early August (Tortorelli, 

2008). Zero streamflow was recorded in water year 2011 

in late May and early June and from late June through 

September, with above-mean streamflow recorded in early 

November 2010 (fig. 12) (U.S. Geological Survey, 2012c). 

Cimarron River near Ripley

Cimarron River near Ripley, Okla. (station number 

07161450, formerly named Cimarron River near Perkins, 

Okla., station number 0716000) is a streamflow-gaging 

station in central Oklahoma (fig. 9). Water year 2011 was 

the fifth driest in the 72 years of record from 1940–2011 at 

that station, with 23 percent of long-term median annual 

streamflow being recorded (table 2). Water year 1953 was the 

driest recorded year at the streamflow-gaging station, with 

17 percent of long-term median annual streamflow being 

recorded. Zero streamflow was not recorded during water 

year 2011, similar to the drought year of 2006, with abovemean streamflow being measured in late May 2011 (fig. 13; 

Tortorelli, 2008). The smallest daily mean streamflow during 

the 2011 water year at this station was 16 ft3/s recorded on 

September 2, 2011 (fig. 13) (U.S. Geological Survey, 2012c).

Illinois River near Tahlequah

Illinois River near Tahlequah, Okla. (station number 

07196500) is a streamflow-gaging station in east-central 

Oklahoma (fig. 9). Water year 2011 was relatively wet, with 

streamflow ranking 63d smallest in the 76 years of record 

from 1936–2011 at the station, with 140 percent of long-term 

median annual streamflow being recorded (table 2). Water 

year 1954 was the driest year recorded at the station, with 

20 percent of long-term median annual streamflow being 

recorded. Zero streamflow was not recorded during water 

year 2011, similar to the drought year of 2006, with some 

above-mean streamflow being recorded in late February 

and early March, late April, May, mid-August, and late 

September of 2011 (fig. 14; Tortorelli, 2008). Large amounts 

of precipitation produced substantial runoff in the watershed 

upstream from the station in April and May, contributing to 

the relatively large median annual streamflow at the site. The 

smallest daily mean streamflow during the 2011 water year at 

this station was 159 ft3/s recorded on September 15, 2011 (fig. 

14) (U.S. Geological Survey, 2012c).

Canadian River at Calvin

Canadian River at Calvin, Okla. (station number 

07231500) is a streamflow-gaging station in east-central 

Oklahoma (fig. 9). Water year 2011 was the fourth driest in 
Streamflow of Long-Term Stations 21

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

10

100

1,000

10,000

100,000

2

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000 Salt Fork Arkansas River at Tonkawa, Okla. 07151000

Streamflow, in cubic feet per second (ft3/s)

3

4

6

1

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1942–2011

Regulated 1942–2011

EXPLANATION

Month

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-1,000

-500

0

500

1,000

1,500

2,000

2,500

3,000

3,500

4,000

Annual departure from

median annual streamflow,

in cubic feet per second (ft3/s)

Salt Fork Arkansas River at Tonkawa, Okla. 07151000

Regulated 1942–2011

droughts: 1952–56 1961–72 1976–81 2011

Hydrologic

Annual departure

Median annual streamflow 812 ft3/s 

5-year weighted average

EXPLANATION

20

Sept

A

B

Data from U.S. Geological Survey (2012b)

Figure 10. Streamflow data for Salt Fork Arkansas River at Tonkawa, Oklahoma, water years 1942–2011. A, Annual departure from 

long-term median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean 

streamflow.
22 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

10

100

1,000

10,000

100,000

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000

Streamflow, in cubic feet per second (ft3/s)

2

3

4

6

1

EXPLANATION

Month

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1937–2011

Chikaskia River near Blackwell, Okla. 07152000

Unregulated 1937–2011

20

Annual departure from

median annual streamflow, in

cubic feet per second (ft3/s)

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-500

0

500

1,000

1,500

2,000

Chikaskia River near Blackwell, Okla. 07152000

Unregulated 1937–2011

EXPLANATION

Annual departure

Median annual streamflow 499 ft3/s 

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Sept

Data from U.S. Geological Survey (2012b)

A

B

Figure 11. Streamflow data for Chikaskia River near Blackwell, Oklahoma, water years 1937–2011. A, Annual departure from long-term 

median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
Streamflow of Long-Term Stations 23

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-500

-250

0

250

500

750

1,000

Annual departure from

median annual streamflow,

in cubic feet per second (ft

3/s)

Cimarron River near Waynoka, Okla. 07158000

Unregulated 1938–2011

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Annual departure

Median annual streamflow 223 ft3/s

5-year weighted average

EXPLANATION

Cimarron River near Waynoka, Okla. 07158000

Streamflow, in cubic feet per second (ft

3/s)

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1938–2011

Unregulated 1938–2011

EXPLANATION

Month

Zero flow

Zero flow

Zero flow

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

1

10

100

1,000

10,000

2

3

4

6

20

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000

Sept

Data from U.S. Geological Survey (2012b)

A

B

Figure 12. Streamflow data for Cimarron River near Waynoka, Oklahoma, water years 1938–2011. A, Annual departure from long-term 

median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
24 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

10

100

1,000

10,000

100,000

20

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000 Cimarron River near Ripley, Okla. 07161450

Streamflow, in cubic feet per second (ft

3/s)

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1940–2011

Unregulated 1940–2011

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-1,500

-500

500

1,500

2,500

Annual departure from

median annual streamflow,

in cubic feet per second (ft

3/s)

Cimarron River near Ripley, Okla. 07161450

Unregulated 1940–2011

EXPLANATION

Annual departure

Median annual streamflow 1,347 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Month

3,500

4,500

5,000

Sept

Data from U.S. Geological Survey (2012b)

A

B

Figure 13. Streamflow data for Cimarron River near Ripley, Oklahoma, water years 1940–2011. A, Annual departure from long-term 

median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
Streamflow of Long-Term Stations 25

Data from U.S. Geological Survey (2012b)

Annual departure from

median annual streamflow,

in cubic feet per second (ft

3/s) Streamflow, in cubic feet per second (ft

3/s)

Month

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

100

1,000

10,000

100,000

1,000,000

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000

200,000

300,000

400,000

600,000 Illinois River near Tahlequah, Okla. 07196500

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1936–2011

Unregulated 1936–2011

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-1,000

-750

-500

-250

0

250

500

750

1,000

1,250

1,500

1,750

2,000

Illinois River near Tahlequah, Okla. 07196500 

Unregulated 1936–2011

EXPLANATION

Annual departure

Median annual streamflow 950 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Sept

A

B

Figure 14. Streamflow data for Illinois River near Tahlequah, Oklahoma, water years 1936–2011. A, Annual departure from long-term 

median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
26 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

the 71 years of record from 1939–42 and 1945–2011, with 

16 percent of the long-term median annual streamflow being 

recorded (table 2). Water year 1981 was the driest year, with 

13 percent of the long-term median annual streamflow being 

recorded. Zero streamflow was not recorded in water year 

2011, with some brief periods of above-mean streamflow 

recorded in late April and late May at the station (fig. 15). Zero 

streamflow was recorded during most of August in the drought 

year of 2006 at this station (Tortorelli, 2008). The smallest 

daily mean streamflow at this station during the 2011 water 

year was 0.40 ft3/s recorded on September 6, 2011 (fig. 15) 

(U.S. Geological Survey, 2012c).

North Canadian River near Wetumka

North Canadian River near Wetumka, Okla. (station 

number 07242000) is a streamflow-gaging station in central 

Oklahoma (fig. 9). Water year 2011 was the ninth driest in the 

74 years of record from 1938–2011, with 31 percent of the 

long-term median annual streamflow being recorded (table 

2). Water year 1956 was the driest year at the station, with 

23 percent of the long-term median annual streamflow being 

recorded. Zero streamflow was not recorded during water year 

2011 at this station, similar to the drought year of 2006, with 

some periods of streamflow near or above the long-term daily 

mean streamflow being recorded in February, April and May 

(fig. 16; Tortorelli, 2008). The smallest daily mean streamflow 

during the 2011 water year was 34 ft3/s recorded at this station 

on August 6, 2011 (fig. 16) (U.S. Geological Survey, 2012c).

Salt Fork Red River at Mangum

Salt Fork Red River near Mangum, Okla. (station number 

07300500) is a streamflow-gaging station in southwestern 

Oklahoma (fig. 9). Water year 2011 was the second driest in 

the 74 years of record from 1938–2011, with 18 percent of the 

long-term median annual streamflow being recorded (table 2). 

Water year 1940 was the driest year recorded at the station, 

with 18 percent of the long-term median annual streamflow 

being recorded. Zero streamflow was recorded in water year 

2011 during part of October 2010 and from mid-May through 

September, with short periods of above-mean streamflow 

measured in October, November, and February (fig. 17) (U.S. 

Geological Survey, 2012c). In the drought year of 2006, zero 

flow was recorded for a shorter period, from late June through 

August at this station (Tortorelli, 2008).

Red River near Gainesville, Texas

Red River near Gainesville, Tex., (station number 

07316000), is a streamflow-gaging station in south-central 

Oklahoma (fig. 9). Water year 2011 was the driest in the 

75 years of record from 1937–2011, with 13 percent of the 

long-term median annual streamflow being recorded (table 2). 

Water year 2006 was the second driest year on record, with 

23 percent of the long-term median annual streamflow being 

recorded at this station. Zero streamflow was not recorded 

during water year 2011 at this station, similar to the drought 

year of 2006, but streamflow remained less than long-term 

daily mean streamflow throughout water year 2011 (fig. 18) 

(Tortorelli, 2008). The smallest daily mean streamflow during 

the 2011 water year at the station was 24 ft3/s recorded on 

September 1, 2011 (fig. 18) (U.S. Geological Survey, 2012c). 

Washita River near Dickson

Washita River near Dickson, Okla. (station number 

07331000) is a streamflow-gaging station in south-central 

Oklahoma (fig. 9). Water year 2011 was the driest in the 

83 years of record from 1929–2011, with 18 percent of the 

long-term median annual streamflow being recorded (table 

2). Water year 1964 was the second driest year recorded at 

this station, with 20 percent of the long-term median annual 

streamflow being recorded. Zero streamflow was not recorded 

during water year 2011 at this station, similar to the drought 

year of 2006, with daily mean streamflow briefly equaling or 

exceeding long-term daily mean streamflow in late May and 

mid-August of 2011 (fig. 19) (Tortorelli, 2008). The smallest 

daily mean streamflow during the 2011 water year was 1.0 

ft3/s recorded at this station on August 8, 2011 (fig. 19) (U.S. 

Geological Survey, 2012c).

Blue River near Blue

Blue River near Blue, Okla. (station number 07332500) 

is a streamflow-gaging station in south-central Oklahoma 

(fig. 9). Water year 2011 was the fourth driest in the 75 years 

of record from 1937–2011, with 28 percent of the long-term 

median annual streamflow being recorded (table 2). Water 

year 1956 was the driest year recorded at the station, with 

12 percent of the long-term median annual streamflow being 

recorded. Zero streamflow was not recorded during water year 

2011 at the station, similar to the drought year of 2006, with 

daily mean streamflow briefly equaling or exceeding longterm daily mean streamflow in late December, late April, and 

late May of 2011 (fig. 20) (Tortorelli, 2008). The smallest 

daily mean streamflow during the 2011 water year at this 

station was 0.24 ft3/s recorded on August 29, 2011 (fig. 20) 

(U.S. Geological Survey, 2012c).

Red River at Arthur City, Texas

Red River at Arthur City, Tex. (station number 07335500) 

is a streamflow-gaging station in southeastern Oklahoma (fig. 

9). Water year 2011 was the second driest in the 67 years of 

record from 1945–2011, with 29 percent of the long-term 

median annual streamflow being recorded (table 2). Water 

year 2006 was the driest year on record for this station, with 
Streamflow of Long-Term Stations 27

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-2,000

-1,000

0

1,000

2,000

3,000

4,000

5,000

Canadian River at Calvin, Okla. 07231500

Unregulated 1939–64 Regulated 1965–2011

EXPLANATION

Annual departure

Median annual streamflow 1,439 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Annual departure from median annual streamflow,

in cubic feet per second (ft3/s)

Data from U.S. Geological Survey (2012b)

Streamflow, in cubic feet per second (ft

3/s)

200

400

600

2,000

4,000

6,000

20,000

40,000

60,000

1

10

100

1,000

10,000

100,000

Canadian River at Calvin, Okla. 07231500

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1939–42, 1945–2011

Regulated 1965–2011

20

40

60

2

4

6

Month

Sept Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

0.1

1,000,000

0.2

0.4

0.6

200,000

400,000

600,000

A

B

Figure 15. Streamflow data for Canadian River at Calvin, Oklahoma, water years 1939–2011. A, Annual departure from long-term 

median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
28 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-1,000

-750

-500

-250

0

250

500

750

1,000

1,250

1,500

1,750

2,000

North Canadian River near Wetumka, Okla. 07242000

Regulated 1938–2011

EXPLANATION

Annual departure

Median annual streamflow 692 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Annual departure from median annual streamflow,

in cubic feet per second (ft3/s) Streamflow, in cubic feet per second (ft

3/s)

Month

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

10

100

1,000

10,000

100,000

20

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000 North Canadian River near Wetumka, Okla. 07242000

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1938–2011

Regulated 1938–2011

Sept

Data from U.S. Geological Survey (2012b)

A

B

Figure 16. Streamflow data for North Canadian River near Wetumka, Oklahoma, water years 1938–2011. A, Annual departure from 

long-term median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily 

mean streamflow.
Streamflow of Long-Term Stations 29

Annual departure from median annual streamflow,

in cubic feet per second (ft3/s)

Streamflow, in cubic feet per second (ft

3/s)

Month

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

1

10

100

1,000

10,000

2

3

4

6

20

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000 Salt Fork Red River at Mangum, Okla. 07300500

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1938–2011

Unregulated 1938–2011

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-100

-50

0

50

100

150

200

250

Salt Fork Red River at Mangum, Okla. 07300500

Unregulated 1938–2011

EXPLANATION

Annual departure

Median annual streamflow 67.7 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Sept

Zero flow

Zero flowZero flow

Data from U.S. Geological Survey (2012b)

A

B

Figure 17. Streamflow data for Salt Fork Red River at Mangum, Oklahoma, water years 1938–2011. A, Annual departure from long-term 

median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
30 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma Annual departure from median annual streamflow,

in cubic feet per second (ft3/s) Streamflow, in cubic feet per second (ft

3/s)

Month

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

10

100

1,000

10,000

100,000

20

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000 Red River near Gainesville, Texas 07316000

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1937–2011

Regulated 1945–2011

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-4,000

-2,000

0

2,000

4,000

6,000

8,000

10,000

Red River near Gainesville, Texas 07316000

Unregulated 1937–1944

Regulated 1945–2011

EXPLANATION

Annual departure

Median annual streamflow 2,508 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Sept

Data from U.S. Geological Survey (2012b)

A

B

Figure 18. Streamflow data for Red River near Gainesville, Texas, water years 1937–2011. A, Annual departure from long-term median 

annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
Streamflow of Long-Term Stations 31

Annual departure from median annual streamflow,

in cubic feet per second (ft3/s) Streamflow, in cubic feet per second (ft

3/s)

Month

10

100

1,000

10,000

100,000

20

30

40

60

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000

Water year

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

Washita River near Dickson, Okla. 07331000

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1929–2011

Regulated 1962–2011

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

-2,000

-1,000

0

1,000

2,000

3,000

4,000

5,000

6,000

Washita River near Dickson, Okla. 07331000

Unregulated 1929–1960

Regulated 1962–2011

EXPLANATION

Annual departure

Median annual streamflow 1,723 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

2

3

4

6

1

Sept

Data from U.S. Geological Survey (2012b)

A

B

Figure 19. Streamflow data for Washita River near Dickson, Oklahoma, water years 1929–2011. A, Annual departure from long-term 

median annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
32 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma Annual departure from median annual streamflow,

in cubic feet per second (ft3/s)

Water year

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010 -500

-250

0

250

500

750

1,000

Blue River near Blue, Okla. 07332500

Unregulated 1937–2011

EXPLANATION

Annual departure

Median annual streamflow 253 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Data from U.S. Geological Survey (2012b)

Streamflow, in cubic feet per second (ft

3/s)

10

100

1,000

10,000

100,000

20

40

60

200

400

600

2,000

4,000

6,000

20,000

40,000

60,000

2

4

6

1

Blue River near Blue, Okla. 07332500

Month

Sept Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

0.2

0.4

0.6

0.1

A

B

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1937–2011

Unregulated 1937–2011

Figure 20. Streamflow data for Blue River near Blue, Oklahoma, water years 1937–2011. A, Annual departure from long-term median 

annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
Groundwater Levels at SelectedLong-Term Stations 33

26 percent of the long-term median annual streamflow being 

recorded. Zero streamflow was not recorded during water 

year 2011 at the station, similar to the drought year of 2006, 

with daily mean streamflow briefly equaling or exceeding 

long-term daily mean streamflow in early February and early 

and late May of 2011 (fig. 21) (Tortorelli, 2008). The smallest 

daily mean streamflow during the 2011 water year at this 

station was 207 ft3/s recorded on September 26, 2011 (fig. 21) 

(U.S. Geological Survey, 2012c).

Effects of Low Streamflows

Hydrologic drought is associated with the effects 

of periods of precipitation deficits on streamflow, lake 

and reservoir levels, and groundwater levels. Although 

all droughts start with precipitation deficits (fig. 1), 

hydrologists are more concerned with how these deficits 

affect the surface-water and groundwater components of 

the hydrologic system. Hydrologic droughts commonly lag 

meteorological and agricultural droughts. During hydrologic 

droughts, precipitation deficiencies take longer to show 

up in components of the hydrologic system. For example, 

precipitation deficits may result in a rapid depletion of soil 

moisture that has an immediate effect on agriculture (Jackson, 

2006a), but the effect of drought on reservoir levels may 

not affect water supply, hydroelectric power production, or 

recreational uses for several months. Water in the hydrologic 

storage systems of rivers and reservoirs commonly has 

multiple and competing purposes including flood control, 

irrigation, recreation, navigation, hydropower, and wildlife 

habitat. Competition for this water escalates during drought 

and conflicts between water users can increase substantially 

(National Drought Mitigation Center, 2012).

Conditions at Major Reservoirs

The hydrologic drought of water year 2011 substantially 

affected reservoirs in the State (table 3, fig. 22) (Oklahoma 

Water Resources Board, 2010a–d, 2011a–j; U.S. Army 

Corps of Engineers, 2012). On September 29, 2011, the day 

before the end of the water year 2011, the statewide total 

conservation storage was 83.3 percent (table 3), which was 

the lowest statewide conservation storage recorded in water 

year 2011 and was slightly less than the conservation storage 

of 86.3 percent available at the end of water year 2006 

(Tortorelli, 2008). The wettest day (having the greatest amount 

of conservation storage) of water year 2011 was April 14, 

2011, when the statewide total conservation storage was the 

highest (100 percent; table 3). The northeastern region of the 

State consistently had the highest percentage of conservation 

storage, whereas the southwestern region of the State 

consistently had the lowest percentage of conservation storage 

(table 3). Lake Altus at Lugert (map identifier 20, fig. 22) in 

the southwestern region was the reservoir with the lowest 

percentage of conservation storage for the entire water year 

2011 (table 3).

The condition of farm ponds across Oklahoma was more 

drastically affected than the major reservoirs with hundreds of 

farm ponds across Oklahoma having completely dried up by 

July 2011, which, along with lack of local hay and high feed 

prices caused widespread sell-offs of State cattle herds (Hayes, 

2011a). In addition to low lake levels and streamflow affecting 

water supplies and recreational tourism, hot, stagnant, 

nutrient-enriched water caused widespread blooms of bluegreen algae (Cyanophyta) in many reservoirs throughout 

the State, which may have caused some illnesses, impaired 

the clarity of water, and caused economic losses to local 

businesses (Cross, 2011; Lawrence, 2012; Sewell, 2011).

Hydroelectric Power Generation

Hydroelectric power generation in Oklahoma was 

substantially reduced at many reservoirs during calendar year 

2011 because of a reduction in available streamflow, as a result 

of the hydrologic drought. Calendar year 2011 hydroelectric 

power generation at stations in Oklahoma ranged from 24 

to 112 percent of the calendar year 2010 power generation, 

with the sum of hydroelectric power generation at nine 

reservoirs declining by 42 percent in 2011 compared to 2010 

(table 4). Reduced hydropower generation during droughts 

in Oklahoma requires substitution of electrical generation 

capacity by combustion of fossil fuels such as coal and natural 

gas (Renewable Energy Policy Network for the 21st century, 

2012). Greater power generation with coal and natural gas, 

typically costs more than hydropower generation and creates 

emissions of additional greenhouse gases and solid wastes 

associated with fossil fuel combustion (Renewable Energy 

Policy Network for the 21st Century, 2012).

Groundwater Levels at Selected

Long-Term Stations

A long-term recording groundwater well that is in 

hydraulic connection with a stream illustrates the effect the 

water year 2011 drought had on groundwater levels in southcentral Oklahoma. The daily mean water level recorded in 

a well completed to 396 feet (ft) below land surface in the 

Arbuckle-Simpson aquifer near Fittstown, Okla., was several 

feet above the long-term daily mean water level in September 

and much of October 2010 but had decreased to about 11 ft 

lower than long-term daily mean water levels by the end of 

water year 2011 (fig. 23A). A well completed to 122 ft below 

land surface in the Arbuckle-Simpson aquifer in an adjoining 

county (Johnston) had similar changes in groundwater levels 

during water year 2011, ending the year at about 5 ft lower 

than long-term daily-mean water levels measured at that well 

(fig. 24A). A well completed to 386 ft below land surface in 
34 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Month

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

100

1,000

10,000

100,000

1,000,000

200

300

400

600

2,000

3,000

4,000

6,000

20,000

30,000

40,000

60,000

200,000

300,000

400,000

600,000 Red River at Arthur City, Texas 07335500

EXPLANATION

Daily mean streamflow, water year 2011

Long-term daily mean streamflow, water years 1945–2011

Regulated 1945–2011

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water year

-10,000

-5,000

0

5,000

10,000

15,000

20,000

Red River at Arthur City, Texas 07335500

Regulated 1945–2011

EXPLANATION

Annual departure

Median annual streamflow 6,909 ft3/s

5-year weighted average

droughts: 1929–41 1952–56 1961–72 1976–81 2011

Hydrologic

Sept

Data from U.S. Geological Survey (2012b)

A

B

Annual departure from median annual streamflow,

in cubic feet per second (ft3/s)

Streamflow, in cubic feet per second (ft

3/s)

Figure 21. Streamflow data for Red River at Arthur City, Texas, water years 1945–2011. A, Annual departure from long-term median 

annual streamflow, and B, Comparison between daily mean streamflow, water year 2011, and long-term daily mean streamflow.
Groundwater Levels at SelectedLong-Term Stations 35

Table 3. Storage in selected major Oklahoma lakes and reservoirs on September 29, 2011, by National Weather Service Climate 

Division, and comparison with April 14, 2011, storage.

[Shading indicates reservoir storage below 80 percent of total conservation storage; WY, water year; Regional totals and averages are based on conservation 

storage in acre-feet for the lakes and reservoirs in each climate division; daily storage numbers above conservation storage amounts are rounded down to 100 

percent, as storage above conservation storage is considered to be in the flood pool of a reservoir; *, indicates seasonal pool operation; actual storage figures/

percents may vary]

Site

number

(fig. 22)

Climate division

lake or reservoir

Conservation 

storage

(acre-feet)

09/29/11

storage

(acre-feet)

Percent of conservation storage

WY end

09/29/11

WY driest

09/01/11

WY wettest

04/14/11

2 North Central

1 Fort Supply 12,221 7,958 65.1 73.1 100

2 Kaw* 437,120 374,569 85.7 86.9 92.1

Regional totals/averages 449,341 382,527 85.1 86.5 92.4

3 Northeast

3 Birch 18,221 13,611 74.7 81.0 96.3

4 Copan 34,647 30,852 89.0 94.7 100

5 Fort Gibson 365,200 353,045 96.7 98.0 100

6 Grand 1,478,860 1,495,291 100 100 100

7 Hudson 200,185 207,372 100 100 100

8 Hulah 22,565 18,395 81.5 91.5 100

9 Keystone 449,961 385,748 85.7 86.2 91.1

10 Oologah 549,300 496,410 90.4 93.3 100

11 Stiatook 323,607 220,149 68.0 62.9 84.2

Regional totals/averages 3,442,546 3,220,873 93.6 94.2 99.8

4 West Central

12 Canton 109,742 68,740 62.6 64.9 100

13 Foss 183,092 144,095 78.7 80.9 92.6

Regional totals/averages 292,834 212,835 72.7 74.9 96.1

5 Central

14 Arcadia 29,546 23,024 77.9 80.1 92.6

15 Heyburn 5,325 4,241 79.6 80.9 100

16 Thunderbird 119,600 91,350 76.4 79.6 84.7

Regional totals/averages 154,471 118,615 76.8 79.8 87.0

6 East Central

17 Eufaula* 2,253,993 1,806,690 80.2 83.0 81.9

18 Tenkiller 654,246 594,260 90.8 91.5 96.3

Regional totals/averages 2,908,239 2,400,950 82.6 84.9 85.2

7 Southwest

19 Fort Cobb 74,030 59,862 80.9 84.4 99.5

20 Altus 128,919 23,232 18.0 18.9 50.8

21 Tom Steed 97,520 58,046 59.5 63.2 82.0

Regional totals/averages 300,469 141,140 47.0 49.4 72.9

8 South Central

22 Arbuckle 72,400 58,844 81.3 84.7 96.5

23 McGee Creek 113,959 97,870 85.9 91.6 93.8

24 Texoma* 2,692,553 2,042,069 75.8 78.2 84.8

25 Waurika* 191,406 147,208 76.9 79.3 93.9

Regional totals/averages 3,070,318 2,345,991 76.4 75.7 86.0

9 Southeast

26 Broken Bow* 919,485 814,390 88.6 88.6 88.7

27 Hugo* 171,009 112,735 65.9 73.9 88.9

28 Pine Creek* 38,608 20,352 52.7 62.0 99.3

29 Sardis 274,192 246,249 89.8 92.2 94.2

30 Wister 49,441 37,364 75.6 83.0 100

Regional totals/averages 1,452,735 1,231,090 84.7 86.7 90.8

State totals 12,070,953 10,054,021 83.3 85.1 100

Resevoirs below 80 percent storage 15 10 1
KANSAS TEXAS COLORADO NEW MEXICO 

Red River Washita RiverCanadian River North Canadian River Cimarron River Arkansas River Verdigris River 

North Fork RedRiver 21 19 17 24 

5 10 2 9 7 29 

27 11 25 13 12 8 4 16 23 

20 

1 22 3 14 15 

96° 96° 98° 98° 100° 100° 102° 102° 

36° 34° 

EXPLANATION <50 51–70 71–80 81–90 91–100 0 25 50 100 MILES 0 25 50 100 KILOMETERS Conservation storage as of September 29, 2011, in percent Numbers at reservoir locations correspond to table 3 Rivers from U.S. Environmental Protection Agency River Reach File version 1 Albers Equal-Area projection North American Datum of 1983

Figure 22. Locations of selected major Oklahoma lakes and reservoirs and percentage of conservation storage as of September 29, 2011.
Groundwater Levels at SelectedLong-Term Stations 37

Table 4. Comparison of hydroelectric power generation at selected Oklahoma hydroelectric plants between calendar years

2010 and 2011.

[GWh, Gigawatt-hour; CY, calendar year]

Site number 

(fig. 22)

Lake hydroelectric

generation project Climate division

Calendar year

2010 power

(GWh)

Calendar year 2011

Power

(GWh)

Percent of 

CY 2010 power

2 Kaw1 2 North Central 110 26 24

5 Fort Gibson2 3 Northeast 252 158 63

6 Grand (Pensacola)3 3 Northeast 528 321 61

7 Hudson (RS Kerr)3 3 Northeast 278 171 62

7 Salina3, 4 3 Northeast 233 229 98

9 Keystone2 3 Northeast 296 68 23

17 Eufaula2 6 East Central 328 96 29

18 Tenkiller2 6 East Central 120 106 88

26 Broken Bow2 9 Southeast 108 121 112

Sum 2,253 1,297 58

1

Data from J. Rogers (Oklahoma Municipal Power Authority, written commun., 2012).

2

Data from A. Corker (Southwestern Power Administration, written commun., 2012).

3

Data from D. Townsend and W. Potter (Grand River Dam Authority, written commun., 2012).

4

Salina Pumped Storage Project, Chimney Rock Reservoir. Water used on the Salina Creek Arm of Lake Hudson, classified as offstream project.

the High Plains aquifer in the panhandle (fig. 25A) did not 

have responses to wet and dry periods during the year, but the 

long-term downward trend in groundwater levels recorded 

since the mid-1960s continued.

The Arbuckle-Simpson aquifer is karstic, consisting 

of highly permeable limestone and dolomite rocks with 

relatively shallow water tables and good hydraulic connection 

to local streams, which contribute to relatively rapid 

responses to precipitation events and drought (Christenson 

and others, 2011). The High Plains aquifer of northwestern 

Oklahoma consists of layers of silty sands with some layers 

of low-permeability caliche. Materials in that aquifer tend to 

have relatively small permeability. Precipitation and recharge 

amounts also tend to be much less in the panhandle than in 

the rest of the State and water tables in the High Plains aquifer 

generally are several hundred feet below land surface (Luckey 

and others, 2000; Wood, 2000). All of those factors combine 

to attenuate short-term water-level changes in wet and dry 

periods in the High Plains aquifer. Long-term declines in 

groundwater levels in the High Plains aquifer are well-known, 

being caused by water withdrawals that exceed recharge in 

that relatively arid area (McGuire, 2011). 
38 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

125

120

115

110

105

100

95

90

Daily mean water level, water year 2011

Long-term daily mean water level, water years 1981–2011

Groundwater well near Fittstown, Okla.

EXPLANATION

Sep

Month

Missing

data

Data from U.S. Geological Survey (2012c)

110

100

90

80

70

65

115

120

125 1958 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2013

Year

EXPLANATION

Continuously recorded water level, water years 2008–12

LOESS curve of measured water levels, water years 1959–2012

Measured water levels, water years 1959–2012

01N–06E–04 CAD 1

A

B

Daily water level, in feet below land surface Water level, in feet below land surface

Figure 23. A, Daily-mean water levels, water year 2011; B, Long-term daily mean water levels and all water levels measured in a 

groundwater well near Fittstown, Oklahoma, water years 1958–2012.
Groundwater Levels at SelectedLong-Term Stations 39

Data from U.S. Geological Survey (2012c)

Water level, in feet below land surface

Month and year

35

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

Daily water level, in feet below land surface

Sept

Month

40

36

31

27

23

19

14

10

EXPLANATION

Daily mean water level, water year 2011

Long-term mean daily water level, water years 2006–11

Groundwater well Johnston 31

01S–05E–31 CBD

EXPLANATION

Continuously recorded water level, water years 2017–12

LOESS curve of measured water levels, water years 2007–12

30

25

20

15

10

5

37.5

Sept Jan Apr July Oct Jan Apr July Oct Jan Apr July Oct Jan Apr July Oct Jan Apr July

2007 2008 2009 2010 2011 2012

Figure 24. A, Daily-mean water levels, water year 2011; B, Long-term daily mean water levels; and continuously recorded water levels 

measured in a groundwater well in Johnston County, Oklahoma, water years 2006–11.

A

B
40 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept Oct

Daily water level, in feet below land surface

Sept

Month

Data from U.S. Geological Survey (2012c)

Water level, in feet below land surface

1956 1960 1965 1970 1975 1980 1985 1990 1995 2000 2005 2010 2013

Year

240

234

229

223

217

211

206

EXPLANATION

Daily mean water level, water year 2011

Long-term mean daily water level water years

1979–97, 2010–11

Groundwater well near Texhoma, Okla.

01N–12E–35 BDD1

180

190

200

210

220

230

EXPLANATION

Continuously recorded water level, water years 2010–12

LOESS curve of measured water levels, water years 1956–2012

Measured water levels, water years 1956–2012

234

201

Figure 25. A, Daily-mean water levels, water year 2011; B, Long-term daily-mean water levels; and continuously recorded water levels 

measured in a groundwater well near Texhoma, Oklahoma, water years 1956–2011.

A

B
References 41

Summary

Water year 2011 (October 1, 2010, through 

September 30, 2011) was a year of hydrologic drought, 

receiving the 2d lowest amount of precipitation and having 

the 16th lowest average annual streamflow and the 42d 

lowest statewide runoff for Oklahoma recorded for the period 

1925–2011. The period of water years 1925–2011 was selected 

as the period of record to examine hydrologic drought in 

this report because before 1925 few continuous record 

streamflow-gaging stations existed and gaps existed where no 

streamflow-gaging stations were operated. In 2011, effects of 

the drought became particularly severe during the summer, 

with the statewide average temperature of 89.1°F during July 

being the hottest month recorded for any State since 1895. 

Some effects of drought during water year 2011 included:

1. streamflow being nearly the smallest recorded for the 

period 1925–2011, particularly in western and southwestern Oklahoma;

2. major reservoirs having only 83.3 percent of the statewide 

conservation storage available at the end of the water 

year;

3. calendar year 2011 hydroelectric power generation at 

stations in Oklahoma being about 58 percent of calendar 

year 2010 power generation;

4. groundwater levels in State aquifers having decreased;

5. wildfires burning more than 300,000 acres and hundreds 

of structures;

6. voluntary and mandatory water-conservation measures 

and mandatory outdoor burn bans being enacted in some 

parts of the State and states of emergency declared;

7. production of many major crops being less than half of 

2010 production;

8. hay and feed prices increasing and many farm ponds drying up, forcing large sales of cattle and, thereby, decreasing cattle herds, which were down to the smallest numbers since 1968;

9. recreational tourism on Oklahoma streams and lakes 

decreasing because of low water levels and blue-green 

algae blooms; and

10. above-normal mortality and poorer condition of many 

species of aquatic and terrestrial wildlife being reported.

The severity of the 2011 drought can be evaluated by 

comparing it with four previous major hydrologic droughts, 

water years 1929–41, 1952–56, 1961–72, and 1976–81. 

Annual area-averaged precipitation totals for the nine National 

Weather Service Climate Divisions from water year 2011 were 

compared to precipitation totals for years in the four previous 

major hydrologic drought periods of the 20th century to show 

how precipitation deficits in Oklahoma varied by region. The 

nine climate divisions in Oklahoma had precipitation in water 

year 2011 ranging from 43 to 76 percent of normal annual 

precipitation, with the Climate Division 3 Northeast having 

the closest to normal precipitation and the Climate Division 

7 Southwest having the greatest percentage of annual deficit. 

Water year 2011 was the second driest of the 1925–2011 

period; only the drought period of 1952–56 had a year with 

less precipitation.

Regional streamflow for water year 2011 indicated that 

streamflow conditions for the Arkansas-White-Red water 

resources region, the 26th lowest since 1930, were considered 

to be normal, despite the very dry conditions in the southern 

and southwestern parts of the region in Oklahoma. Twelve 

long-term streamflow-gaging stations with periods of record 

ranging from 67 to 83 years were selected to show how 

streamflow deficits varied by region in the State. Statewide, 

water year 2011 had average annual streamflow that was the 

16th lowest, and statewide runoff that was the 42d lowest 

of the period 1925–2011, more than was measured in years 

during the drought periods of 1929–41, 1952–56, 1961–72, 

and 1976–81. The hydrologic drought worsened from the 

northeast toward the southwest in Oklahoma, ranging from 

streamflows 140 percent above normal in the northeast to 

13 percent of normal in the southwest. The Red River near 

Gainesville, Texas, long-term streamflow-gaging station in 

southwestern Oklahoma, had 13 percent of normal annual 

streamflow, the smallest long-term median annual streamflow 

recorded at that station for the period 1937–2011. In the 

central part of the State, the North Canadian River near 

Wetumka, long-term streamflow-gaging station, had 31 

percent of normal long-term median annual streamflow. 

Conversely, in the northeastern part of the State, the Illinois 

River near Tahlequah, long-term streamflow-gaging station, 

had 140 percent of normal long-term median annual 

streamflow. Below-normal streamflow in much of the State 

resulted in major reservoirs containing 83.3 percent of the 

statewide conservation storage at the end of the water year.

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Appendixes 1–4 47

Appendixes 1–4

Photographs of Selected Sites at Normal/High-Flow Conditions

and Drought/Low-Flow Conditions, 2007–12
Appendix 1. Looking east from the northwest corner of Lake Overholser near Ramsey Road in Oklahoma City, Oklahoma, during normal conditions in conditions in September 2011.
Appendixes 1–4 49

W.J. Andrews, USGS Photograph

S.J. Smith, USGS Photograph

Appendix 2. Dock on southwestern corner of Lake Hefner in Oklahoma City, Oklahoma, during 

normal conditions in July 2012 and drought conditions in October 2011.
50 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

W.J. Andrews, USGS Photograph

J.C. Scott, USGS Photograph

Appendix 3. Marina at the southwestern corner of Lake Hefner in Oklahoma City, Oklahoma, during 

normal conditions in July 2012 and drought conditions in September 2011.
Appendixes 1–4 51

J.A. Savoia, USGS Photograph

J.A. Savoia, USGS Photograph

Appendix 4. North Canadian River near Calumet, Oklahoma, during floods of July 2007 and drought 

conditions in July 2011.
52 Hydrologic Drought of Water Year 2011 Compared to Four Major Drought Periods of the 20th Century in Oklahoma

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