U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2008-5199

Prepared in cooperation with the Oklahoma Water Resources Board

Hydrologic Drought of Water Year 2006 Compared with Four 

Major Drought Periods of the 20th Century in Oklahoma

Canadian River downstream from State Highway 99 near Ada August 16, 2006

Canadian River near Norman February 1952
Front Cover: Picture One shows wind ripples and river silts, Canadian River near Norman, Cleveland County, Oklahoma, taken February 1952. Photographer: W.B. Hamilton, from U.S. Geological Survey Photographic Library.

Picture Two shows the dry Canadian River near Ada, Pontotoc County, Oklahoma, downstream from State Highway 99, taken August 16, 2006. Photographer: Daniel Fenner, U.S. Fish and Wildlife Service.
Hydrologic Drought of Water Year 2006 

Compared with Four Major Drought Periods 

Of the 20th Century in Oklahoma

By Robert L. Tortorelli

Prepared in cooperation with the Oklahoma Water Resources Board

Scientific Investigations Report 2008–5199

U.S. Department of the Interior

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

DIRK KEMPTHORNE, Secretary

U.S. Geological Survey

Mark D. Myers, Director

U.S. Geological Survey, Reston, Virginia: 2008

This and other USGS information products are available at:

http://store.usgs.gov/

U.S. Geological Survey

Box 25286, Denver Federal Center

Denver, CO 80225

To learn about the USGS and its information products visit http://www.usgs.gov/

1-888-ASK-USGS

Any use of trade, product, or firm names is for descriptive purposes only and does not imply endorsement by the 

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:

Tortorelli, R.L., 2008, Hydrologic drought of Water Year 2006 compared with four major drought periods of the 20th 

century in Oklahoma: U.S. Geological Survey Scientific Investigations Report 2008–5199, 46 p.
iii

Contents

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

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

Purpose and Scope ..............................................................................................................................2

Progression of Drought ........................................................................................................................2

Definition of Drought Sequence ................................................................................................2

Drought Monitor ...........................................................................................................................2

Statewide Precipitation and Streamflow ..........................................................................................2

Acknowledgments ................................................................................................................................7

Precipitation by Climate Division ................................................................................................................7

Climate Division 1 Panhandle ...........................................................................................................12

Climate Division 2 North Central ......................................................................................................12

Climate Division 3 Northeast .............................................................................................................12

Climate Division 4 West Central .......................................................................................................12

Climate Division 5 Central ..................................................................................................................14

Climate Division 6 East Central .........................................................................................................14

Climate Division 7 Southwest ...........................................................................................................14

Climate Division 8 South Central ......................................................................................................14

Climate Division 9 Southeast ............................................................................................................14

Streamflow of Long-Term Sites .................................................................................................................14

Salt Fork Arkansas River at Tonkawa ..............................................................................................14

Chikaskia River near Blackwell ........................................................................................................14

Cimarron River near Waynoka ..........................................................................................................27

Cimarron River near Ripley ...............................................................................................................27

Illinois River near Tahlequah .............................................................................................................27

Canadian River at Calvin ....................................................................................................................27

North Canadian River near Wetumka ..............................................................................................27

Salt Fork Red River at Mangum ........................................................................................................27

Red River near Gainesville, Texas ....................................................................................................27

Washita River near Dickson ..............................................................................................................28

Blue River near Blue...........................................................................................................................28

Red River at Arthur City, Texas .........................................................................................................28

Effects of Low Streamflows .......................................................................................................................28

Conditions at Major Reservoirs ........................................................................................................28

Hydroelectric Power Generation .....................................................................................................28

Ground Water at a Long-Term Site ..................................................................................................34

Wildfires ...............................................................................................................................................34

Summary........................................................................................................................................................34

Selected References ...................................................................................................................................36

Appendixes ...................................................................................................................................................39

 1–7. Photographs showing:

 1. Salt Fork of Arkansas River at Tonkawa (0751000), showing low flow, 30 cubic 

feet per second, looking upstream from U.S. Highway 77 bridge, August 6, 2006.. .........41
iv

 2. Chikaskia River near Blackwell (07152000), showing low flow, 74 cubic feet per 
v

10–21. Graphs showing:

 10. Salt Fork Arkansas River at Tonkawa (A) annual departure from long-term

median annual streamflow, water years 1942–2006 (B) comparing daily-mean

streamflow of Water Year 2006 and long-term daily-mean streamflow, water

years 1942–2006...................................................................................................................18

 11. Chikaskia River near Blackwell (A) annual departure from long-term median

annual streamflow, water years 1937–2006 (B) comparing daily-mean

streamflow of Water Year 2006 and long-term daily-mean streamflow, water

years 1937–2006...................................................................................................................19

 12. Cimarron River near Waynoka (A) annual departure from long-term median

annual streamflow, water years 1938–2006 (B) comparing daily-mean

streamflow of Water Year 2006 and long-term daily-mean streamflow,

water years 1938–2006. ......................................................................................................20

 13. Cimarron River near Ripley (A) annual departure from long-term median 

annual streamflow, water years 1940–2006 (B) comparing daily-mean 

streamflow of Water Year 2006 and long-term daily-mean streamflow, water 

years 1940–2006. Includes streamflow record 1940–87 from nearby station 

0716100, Cimarron River at Perkins. .................................................................................21

 14. Illinois River near Tahlequah (A) annual departure from long-term median 

annual streamflow, water years 1936–2006 (B) comparing daily-mean 

streamflow of Water Year 2006 and long-term daily-mean streamflow, water 

years 1936–2006...................................................................................................................22

 15. Canadian River at Calvin (A) annual departure from long-term median annual

streamflow, water years 1939–2006 (B) comparing daily-mean streamflow 

of Water Year 2006 and long-term daily-mean streamflow, water years 

1939–2006..............................................................................................................................23

 16. North Canadian River near Wetumka (A) annual departure from long-term 

median annual streamflow, water years 1938–2006 (B) comparing daily-mean

streamflow of Water Year 2006 and long-term daily-mean streamflow, water 

years 1938–2006...................................................................................................................24

 17. Salt Fork Red River at Mangum (A) annual departure from long-term median

annual streamflow, water years 1938–2006 (B) comparing daily-mean 

streamflow of Water Year 2006 and long-term daily-mean streamflow, water 

years 1938–2006...................................................................................................................25

 18. Red River near Gainesville, Texas, (A) annual departure from long-term median

annual streamflow, water years 1937–2006 (B) comparing daily-mean 

streamflow of Water Year 2006 and long-term daily-mean streamflow, water 

years 1937–2006...................................................................................................................26

 19. Washita River near Dickson (A) annual departure from long-term median 

annual streamflow, water years 1929–2006 (B) comparing daily-mean 

streamflow of Water Year 2006 and long-term daily-mean streamflow, water 

years 1929–2006...................................................................................................................29

 20. Blue River near Blue (A) annual departure from long-term median annual 

streamflow, water years 1937–2006 (B) comparing daily-mean streamflow of 

Water Year 2006 and long-term daily-mean streamflow, water years 

1937–2006..............................................................................................................................30

 21. Red River at Arthur City, Texas, (A) annual departure from long-term median

annual streamflow, water years 1945–2006 (B) comparing daily-mean 

streamflow of Water Year 2006 and long-term daily-mean streamflow, water 

years 1945–2006...................................................................................................................31
vi

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

percent of Conservation Storage as of October 4, 2006.......................................................32

23. Graph showing Fittstown ground-water well, comparing daily water levels for 

Water Year 2006 and long-term mean-daily water levels, water years 1981–2006. ........36

Tables

1. Summary of precipitation at Climate Divisions in Oklahoma comparing the median 

of mean annual precipitation during water years 1925-2006 with average annual 

precipitation during periods of previous documented hydrologic droughts and 

the recent hydrologic drought period. ....................................................................................10

2. Summary of streamflow conditions at selected long-term streamflow-gaging 

stations in Oklahoma comparing the median of mean annual streamflow with 

average annual streamflow during periods of previous documented hydrologic 

droughts and the recent hydrologic drought period.............................................................16

3. Storage in selected major Oklahoma lakes and reservoirs during October 4, 2006, 

by National Weather Service Climate Division, and comparison with December 21, 

2005, and May 24, 2006, storage. .............................................................................................33

4. Comparison of hydroelectric power generation at selected Oklahoma hydroelectric 

plants between Calendar Year 2005 and Water Year 2006...................................................35

Conversion Factors and Datums

Multiply By To obtain

Length

inch (in.) 2.54 centimeter (cm)

inch (in.) 25.4 millimeter (mm)

foot (ft) 0.3048 meter (m)

Area

square mile (mi2

) 2.590 square kilometer (km2) 

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)

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 the water year ends.
Abstract

Water Year 2006 (October 1, 2005, to September 30, 

2006) was a year of extreme hydrologic drought and the driest year in the recent 2002–2006 drought in Oklahoma. The 

severity of this recent drought can be evaluated by comparing it with four previous major hydrologic droughts, water 

years 1929–41, 1952–56, 1961–72, and 1976–81. The U.S. 

Geological Survey, in cooperation with the Oklahoma Water 

Resources Board, completed an investigation to summarize 

the Water Year 2006 hydrologic drought and compare it to the 

four previous major hydrologic droughts in the 20th century.

The period of water years 1925–2006 was selected as the 

period of record because before 1925 few continuous record 

streamflow-gaging sites existed and gaps existed where no 

streamflow-gaging sites were operated. Statewide annual precipitation in Water Year 2006 was second driest and statewide 

annual runoff in Water Year 2006 was sixth driest in the 

82 years of record. 

Annual area-averaged precipitation totals by the nine 

National Weather Service Climate Divisions from Water Year 

2006 are compared to those during four previous major hydrologic droughts to show how rainfall deficits in Oklahoma varied by region. Only two of the nine climate divisions, Climate 

Division 1 Panhandle and Climate Division 4 West Central, 

had minor rainfall deficits, while the rest of the climate divisions had severe rainfall deficits in Water Year 2006 ranging 

from only 65 to 73 percent of normal annual precipitation.

Regional streamflow patterns for Water Year 2006 indicate that Oklahoma was part of the regionwide below-normal 

streamflow conditions for Arkansas-White-Red River Basin, 

the sixth driest since 1930. The percentage of long-term stations in Oklahoma (with at least 30 years of record) having 

below-normal streamflow reached 80 to 85 percent for some 

days in August and November 2006.

 Twelve long-term streamflow-gaging sites with periods 

of record ranging from 62 to 78 years were selected to show 

how streamflow deficits varied by region. The hydrologic 

drought worsened going from north to south in Oklahoma, 

ranging from 45 percent in the north, to just 14 percent in eastcentral Oklahoma, and 20 percent of normal annual streamflow in the southwest.

The low streamflows resulted in only 86.3 percent of 

the statewide conservation storage available at the end of the 

water year in major reservoirs, and 7 to 47 percent of hydroelectric power generation at sites in Oklahoma in Calendar 

Year 2005.

Introduction

Water Year 2006 (October 1, 2005, to September 30, 

2006) was a year of extreme hydrologic drought and the driest 

year in the recent 2002–2006 drought in Oklahoma. A sense of 

the severity of this recent drought can be evaluated by comparing Water Year 2006 hydrologic drought with four previous 

major hydrologic droughts, water years 1929–41, 1952–56, 

1961–72, and 1976–81. The effect of the drought varies in 

different regions of the state. Data from several long-term 

streamflow-gaging stations are available to assess the effect of 

the hydrologic drought of Water Year 2006 in Oklahoma.

Hydrologic drought is associated with the effects of 

periods of precipitation deficits on surface or subsurface water 

supply. The frequency and severity of hydrologic drought 

is defined on a watershed or river basin scale. Water in the 

hydrologic storage systems, 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 increase substantially 

(National Drought Mitigation Center, 2006a).

The U.S. Geological Survey (USGS), in cooperation with 

the Oklahoma Water Resources Board, completed an investigation to summarize the Water Year 2006 hydrologic drought 

and compare it to the four previous major hydrologic droughts 

in the 20th century.

Hydrologic Drought of Water Year 2006 Compared 

With Four Major Drought Periods of the 20th Century

In Oklahoma

By Robert L. Tortorelli
2 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Purpose and Scope

The purpose of this report is to describe and document 

the Water Year 2006 hydrologic drought in Oklahoma and 

compare it to four previous major hydrologic droughts, water 

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

A brief introduction includes (1) a definition of drought 

sequence, (2) a presentation of monthly nationwide drought 

monitor graphics for Water Year 2006, and (3) a comparison of 

annual statewide total precipitation and statewide streamflow 

runoff from water years 1925–2006 in Oklahoma with the four 

previous major hydrologic droughts in the 20th century highlighted. Annual area-averaged precipitation totals for Water 

Year 2006 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 rainfall deficits varied by region. Next the mean 

annual streamflow during Water Year 2006 at 12 long-term 

streamflow-gaging sites are compared to streamflow during 

four previous major hydrologic droughts in the 20th century 

to show how streamflow deficits varied by region. The effects 

of low streamflows are discussed to include (1) conservation 

storage at major reservoirs throughout the state, (2) hydroelectric power generation, (3) ground-water levels at a long-term 

site, and (4) wildfires.

The effects of the hydrologic drought of Water Year 2006 

on agriculture are beyond the scope of this report and a discussion can be found in Oklahoma Agricultural Statistics 2007 

(National Agricultural Statistics Service, 2007).

Progression of Drought

Definition of Drought Sequence

The drought sequence development is illustrated in figure 

1. The start of 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 is experienced. If the drought continues for several seasons, streamflow is reduced to critical levels and “hydrologic” drought 

results (Oklahoma Water Resources Board, 2007a; National 

Drought Mitigation Center, 2006a). 

Drought Monitor

The U.S. Drought Monitor is a graphic depiction of 

broad-scale drought in the United States displayed on the 

National Drought Mitigation Center web page (National 

Drought Mitigation Center, 2007). Agricultural and hydrologic 

drought effects are displayed on a weekly graphic accompanied by tabular data and general regional narratives for that 

week. 

Figure 2 shows the progression of the Water Year 2006 

drought with 12 monthly Drought Monitor graphs from 

November 1, 2005, to October 3, 2006. The hydrologic 

drought of Water Year 2006 in Oklahoma is shown getting 

steadily worse from November through March, improving 

with some spring and summer rains from April through the 

beginning of July and then the drought is worst in August. 

Conditions improved in September and October.

Statewide Precipitation and Streamflow

Precipitation and runoff plots help to characterize the 

duration and severity of hydrologic drought by comparing 

annual statewide precipitation and runoff departures from 

long-term median values. Annual departures are shown as 

positive bars when annual departures exceed the long-term 

median and as negative bars when annual departures are 

less than the long-term median. Thus departures that are 

consistently negative over several years provide a measure 

of drought duration or persistence, while the magnitude of 

individual departures provides a measure of severity. Negative 

departure of runoff also can be characterized as runoff deficits.

The period of water years 1925–2006 was selected as 

the period of record for long-term drought analysis. Few 

continuous record streamflow-gaging sites existed and there 

were record year gaps where no streamflow-gaging sites were 

operated before 1925 (U.S. Geological Survey, 2007a). The 

four previous major hydrologic drought periods, water years 

1929–41, 1952–56, 1961–72, and 1976–81 were identified 

from the statewide runoff plot and modified from a previous 

drought report by Tortorelli and others (1991). The 2002–2006 

hydrologic drought period was identified from the statewide 

runoff plot.

Figures 3 and 4 show how annual statewide precipitation 

and annual statewide median runoff compare during water 

years 1925–2006. First, the statewide annual mean precipitation for each water year of the period (National Climatic Data 

Center, 2007a) is plotted as the departure from the median 

annual precipitation for the period (“normal” annual precipitation, blue line), and a 5-year weighted-average departure precipitation is plotted as a red line (fig. 3). The selected drought 

periods are indicated by different colored annual bars. Water 

Year 2006 was second driest in the 82 years of record from 

1925–2006. 

Second, the statewide annual median runoff for each 

water year of the period (U.S. Geological Survey, 2007a) is 

plotted as the departure from the median annual runoff for 

the period (“normal” annual runoff, blue line), and a 5-year 

weighted-average departure runoff is plotted as a red line 

(fig. 4). The selected drought periods are indicated by different 

colored annual bars. Based on runoff, Water Year 2006 was 

sixth driest in the 82 years of record from 1925–2006.

Wetter years plot above the median line and drier years 

plot below the median line. Water Year 2006 then can be compared to the dry years in the four previous major hydrologic 

droughts by depth of the bars. The length and severity of the 

water year 2002–2006 drought period also can be compared 
Introduction 3

Figure 1. Sequence of drought development (Oklahoma Water Resources Board, 2007a; modified from National Drought Mitigation 

Center, 2006a)
4 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Figure 2. Monthly Drought Monitor Graphs, November 1, 2005, through October 3, 2006, (National Drought Mitigation Center, 

2007) —Continued
Introduction 5

Figure 2. Monthly Drought Monitor Graphs, November 1, 2005, through October 3, 2006, (National Drought Mitigation Center, 2007).
6 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

28

24

20

16

12

8

4

0

-4

-8

-12

-16

Oklahoma Statewide Precipitation

1925-2006 Annual Departure

Long-Term Median Annual Precipitation 33.51 inches

5-year Weighted Average

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a

A

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de

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s

M

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m

cn

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i

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i

rutrapeDl

Hydrologic

au

Droughts: 1929-41 1952-56 1961-72 1976-81 2002-06

n

920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

1

nA

-20

Figure 3. Oklahoma statewide precipitation showing the annual departure from the long-term statewide median of 33.51 inches (blue 

line) and a 5-year weighted average line for water years 1925–2006 (red line). Wetter years plot above the median line and drier years 

plot below the median line.

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

10

8

6

4

2

0

-2

-4

Oklahoma Statewide Runoff

1925-2006

Annual Departure

Long-Term Median Annual Runoff 3 inches

5-year Weighted Average

,ffonuRlaunnA

ra

n

e

ai

y

d

r

e

e

M

p

m

se

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fr

c

n

e

i

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in

tr apeDlaun

Hydrologic

nA

Droughts: 1929-41 1952-56 1961-72 1976-81 2002-06

Figure 4. Oklahoma statewide runoff showing the annual departure from the long-term statewide median of 3 inches (blue line) and a 

5-year weighted average line for water years 1925–2006 (red line). Wetter years plot above the median line and drier years plot below 

the median line.
Precipitation By Climate Division 7

to the four previous major hydrologic drought periods by the 

5-year weighted average line.

The hydrologic drought of water years 1929–41 was 

known as the “Dust Bowl” years in the Great Plains and is 

documented in several references (Hoyt, 1936 and 1938; Nace 

and Pluhowski, 1965; Egan, 2006; National Drought Mitigation Center, 2006b). This drought was particularly severe in 

western Oklahoma with a deficit runoff in 1934; whereas, 

major wind erosion happened over the entire state in 1936 

(Nace and Pluhowski, 1965). The 1929–41 drought triggered 

nationwide soil conservation measures (National Drought 

Mitigation Center, 2006b). 

The hydrologic drought of water years 1952–56 was the 

most widespread and the most severe for all regions of Oklahoma for precipitation and in most regions for runoff than the 

other hydrologic drought periods (Nace and Pluhowski, 1965; 

Tortorelli and others, 1991; figs. 3–4). This drought prompted 

the construction of Atoka Lake to provide a reliable water supply for Oklahoma City (Johnson, 1956) and prompted many 

Oklahoma communities to plan for long-term water supply.

The hydrologic drought of water years 1961–72 also was 

widespread and lasted longer than that in 1952–56 but generally was not as severe (Tortorelli and others, 1991; figs. 3-4). 

By this time many of the major reservoirs in Oklahoma were 

completed (Vance, 2007).

The hydrologic drought of water years 1976–81 also was 

widespread, but was not as severe or persistent as the previous 

three major droughts (Tortorelli and others, 1991; figs. 3-4).

The precipitation and runoff plots in figures 3 and 4 

indicate that Water Year 2006 was very dry (second lowest 

statewide precipitation in the 1925–2006 study period) with 

very low statewide runoff (sixth lowest in the 1925–2006 

study period). On that basis, drought conditions in Water Year 

2006 were severe, but drought duration or persistence cannot 

yet be characterized (October 2006).

Regional streamflow patterns for Water Year 2006 

(fig. 5) indicate that Oklahoma was part of the regionwide 

below-normal streamflow for the Arkansas-White-Red River 

Basin, the sixth driest since 1930 (U.S. Geological Survey, 

2008a). Figure 6 shows the percentage of 82 long-term streamflow stations in Oklahoma (at least 30 years of record) having 

below normal streamflow during the water year 2002–2006 

drought period (U.S. Geological Survey, 2008b). As indicated 

by the dashed line in figure 6, about 25 percent of all stations 

can be expected to have streamflow below normal at any given 

time, where normal streamflow is considered to be within the 

25th and 75th percentile at each site. Figure 6 shows that for 

some days in August and November 2006, the percentage of 

long-term stations having below-normal streamflow reached 

80 to 85 percent.

Acknowledgments

The author thanks many people for their contributions to 

the data collection and data analysis presented in this report. 

Deke Arndt of Oklahoma Climatological Survey supplied 

Water Year 2006 precipitation maps and Brian Vance of 

the Oklahoma Water Resources Board provided a modified 

Drought Sequence diagram from the National Drought Mitigation Center. Additional special thanks go to Daniel Fenner of 

the U.S. Fish and Wildlife Service for providing photographs 

of low flow in August 2006 at numerous sites along the reach 

of the Canadian River above Calvin. Rachel Esralew of the 

Oklahoma Water Science Center compiled site maps. USGS 

personnel provided low flow photographs in August 2006 at 

USGS streamflow gages. The Oklahoma Publishing Company 

provided the photograph of Thunderbird Lake shoreline on the 

back cover. 

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, 2007b). 

These data were totaled for each water year from 1925–2006. 

These totals give a sense of annual precipitation in Oklahoma 

on a regional basis. 

Table 1 shows how Water Year 2006 precipitation compares with that during the driest year from each of the four 

previous major hydrologic droughts within each of the nine 

National Weather Service Climate Divisions to show how 

rainfall deficits in Oklahoma varied by region. Table 1 also 

shows how the annual precipitation for the selected years compares with the long-term median annual precipitation values 

for water years 1925–2006 (“normal”) and the ranking (lowest 

ranking associated with driest year). Precipitation in water 

year 2006 was slightly less than the long-term climate division 

median in two of the nine climate divisions, Climate Division 

1 Panhandle and Climate Division 4 West Central (minor rainfall deficits of 85 percent or more of normal precipitation). In 

all other climate divisions, Water Year 2006 precipitation was 

substantially less then the long-term climate division medians, 

with severe rainfall deficits ranging from only 65 to 73 percent 

of normal annual precipitation. Table 1 also shows that statewide precipitation Water Year 2006 was second driest in the 

82 years of record from 1925–2006 and was only 72 percent 

of the normal precipitation. Only one year in the 1925–2006 

period was drier, Water Year 1956 with only 56 percent of 

normal precipitation. 

The Oklahoma Mesonet, a statewide network of environment monitoring stations, consists of 115 automated stations 

covering Oklahoma and provides 5-minute precipitation 

data. At least one station is located in each of 77 Oklahoma 

counties. Oklahoma Mesonet climate data are available since 

1994, but were not used for this report so that data from one 

source (National Climatic Data Center, 2007b) for the period 

1925–2006 would be used. In addition, Mesonet data uses 

mean annual precipitation from calendar years 1971–2000 

as “normal” instead of median annual precipitation from 
8 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Figure 5. Regional streamflow patterns Water Year 2006 (U.S. Geological Survey, 2008a).
Precipitation By Climate Division 9

EXPLANATION

The

d each day as the percent of streamflow gages having below normal flow, where

the lower bound for normal is the 25th percentile value (dotted line) among all historical values

for all days of the year. The percent of stations below normal is based only on streamflow

gages in the state having at least 30 years of record

Percent of Stations Below Normal Streamflow, plotted as the red line on the above graph,

is calculate Percent of Stations Below Normal Streamflow

2001 2002 2003 2004 2005 2006 2007

0

10

20

30

40

50

60

70

80

90

100

Expected percentage

Since January 16, 2001

Oklahoma [82 sites]

Year

Figure 6. Percentage of stations below normal streamflow since January 16, 2001, through February 1, 2008, in Oklahoma (U.S. 

Geological Survey, 2007c).
10 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Table 1. Summary of precipitation at 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 previous documented hydrologic droughts and the recent hydrologic drought period.

[avg, average; %, percent; Rank, rank of driest year of drought period out of period WY 1925-2006; WY, water year; SW, statewide]

Hydrologic Drought Periods

1929-41 3 1952-56 3

Lowest year / Rank Lowest year / Rank

Climate 

Division

number 

Climate Division name

Long-term 

annual 

median

(inches)

WY avg 

annual 

precipitation

(inches)

Percent longterm median

WY Avg 

annual 

precipitation

(inches)

Percent longterm median

SW Statewide 1 33.51 1936 5 1956 1

25.24 75% 18.68 56%

1 Panhandle 2 19.54 1937 2 1956 1

12.24 63% 11.34 58%

2 North Central 2 28.94 1936 6 1956 1

20.16 70% 15.10 52%

3 Northeast 2 38.96 1939 8 1956 1

30.59 79% 22.90 59%

4 West Central 2 26.55 1940 8 1952 1

20.14 76% 15.98 60%

5 Central 2 33.73 1936 2 1956 1

24.03 71% 19.74 59%

6 East Central 2 42.91 1936 3 1956 1

28.11 66% 23.86 56%

7 Southwest 2 27.56 1939 4 1956 1

18.75 68% 17.45 63%

8 South Central 2 36.63 1939 2 1956 1

24.19 66% 16.46 45%

9 Southeast 2 48.51 1934 2 1956 1

30.86 64% 25.10 52%

1

 Ranks from Statewide Monthly Precipitation Totals, National Climatic Data Center (2007a)

2

 Ranks from Climate Division Monthly Precipitation Totals, National Climatic Data Center (2007b).

3

 Documented drought periods are modified from Tortorelli and others, 1991.
Precipitation By Climate Division 11

Table 1. Summary of precipitation at 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 previous 

documented hydrologic droughts and the recent hydrologic drought period.

[avg, average; %, percent; Rank, rank of driest year of drought period out of period WY 1925-2006; WY, water year; SW, statewide]

Hydrologic Drought Periods

1961-72 3 1976-1981 3 2002-2006 2006

Lowest Year / Rank Lowest Year / Rank Lowest Year / Rank Rank

Climate 

Division 

number

WY avg 

annual 

precipitation

(inches)

Percent 

long-term 

median

WY avg 

annual 

precipitation

(inches)

Percent 

long-term 

median

WY avg 

annual 

precipitation 

(inches)

Percent 

long-term 

median

WY avg 

annual

 precipitation

(inches)

Percent 

long-term 

median

SW 1963 3 1978 10 2006 2 2

24.60 73% 27.11 81% 24.12 72% 24.12 72%

1 1970 4 1976 29 2002 15 22

13.05 67% 17.58 90% 15.34 79% 16.69 85%

2 1966 5 1976 14 2006 7 7

20.15 70% 23.24 80% 20.23 70% 20.23 70%

3 1963 2 1981 14 2006 5 5

24.81 64% 32.89 84% 28.29 73% 28.29 73%

4 1970 3 1976 24 2002 19 28

18.00 68% 22.23 84% 21.90 82% 23.46 88%

5 1972 6 1976 7 2006 3 3

25.08 74% 25.41 75% 24.17 72% 24.17 72%

6 1963 4 1980 6 2006 2 2

28.24 66% 30.30 71% 27.70 65% 27.70 65%

7 1967 2 1980 23 2006 3 3

17.46 63% 23.40 85% 18.59 67% 18.59 67%

8 1963 4 1978 8 2006 3 3

25.15 69% 27.78 76% 24.45 67% 24.45 67%

9 1963 7 1978 3 2006 6 6

35.02 72% 31.95 66% 34.89 72% 34.89 72%
12 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

water years 1925–2006. This period contains an extremely 

wet period (fig. 3); therefore, data presented on the Mesonet 

website (fig. 8; Oklahoma Climatological Survey, 2008a, 

2008b) indicated more severe precipitation deficits in 2006 

than in table 1. However, these data do show how Water Year 

2006 differs from normal and give a sense of regional rainfall 

deficits. 

Climate Division 1 Panhandle

Climate Division 1 Panhandle is in far northwest Oklahoma. Water Year 2006 was the 22nd driest in the 82 years of 

record from 1925–2006, with 16.69 inches of rainfall, a deficit 

of 2.85 inches or 85 percent of normal area precipitation (table 

1). Water Year 1956 was the driest year, from the 1952–56 

drought period, with only 11.34 inches of rainfall, a deficit of 

8.20 inches or 58 percent of normal annual area precipitation. 

Climate Division 2 North Central

Climate Division 2 North Central is in north-central 

Oklahoma. Water Year 2006 was the seventh driest in the 

82 years of record from 1925–2006, with 20.23 inches of 

rainfall, a deficit of 8.71 inches or 70 percent of normal area 

precipitation (table 1). Water Year 1956 was the driest year, 

from the 1952–56 drought period, with only 15.10 inches 

of rainfall, a deficit of 13.84 inches or 52 percent of normal 

annual area precipitation. 

Climate Division 3 Northeast

Climate Division 3 Northeast is in northeast Oklahoma. 

Water Year 2006 was the fifth driest in the 82 years of record 

from 1925–2006, with 28.29 inches of rainfall, a deficit of 

10.67 inches or 73 percent of normal area precipitation 

(table 1). Water Year 1956 was the driest year, from the 

1952–56 drought period, with only 22.90 inches of rainfall, 

a deficit of 16.06 inches or 59 percent of normal annual area 

precipitation. 

Climate Division 4 West Central

Climate Division 4 West Central is in west-central Oklahoma. Water Year 2006 was the 28th driest in the 82 years of 

record from 1925–2006, with 23.46 inches of rainfall, a deficit 

of 3.09 inches or 88 percent of normal area precipitation 

(table 1). Water Year 1952 was the driest year, from the 

1952–56 drought period, with only 15.98 inches of rainfall, 

a deficit of 10.57 inches or 60 percent of normal annual area 

precipitation. 

1 2 3

4

5

6

7

8 9

CENTRAL

NORTHEAST

PANHANDLE

SOUTHWEST

SOUTHEAST

SOUTH

CENTRAL

NORTH CENTRAL

EAST

CENTRAL

WEST

CENTRAL

OKLAHOMA

0 200100 KILOMETERS

0 100 200 50 MILES

Climate Division number

and name

5 CENTRAL

Albers Equal Area Conic Projection

Figure 7. National Weather Service Climate Divisions in Oklahoma.
Precipitation By Climate Division 13

Figure 8. Oklahoma (A) percent of normal rainfall, Water Year 2006 (Oklahoma Climatological Survey, 2008a) (B) departure from normal 

rainfall, Water Year 2006 (Oklahoma Climatological Survey, 2008b).
14 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Climate Division 5 Central

Climate Division 5 Central is in central Oklahoma. Water 

Year 2006 was the third driest in the 82 years of record from 

1925–2006, with 24.17 inches of rainfall, a deficit of 

9.56 inches or 72 percent of normal area precipitation 

(table 1). Water Year 1956 was the driest year, from the 

1952–56 drought period, with only 19.74 inches of rainfall, 

a deficit of 13.99 inches or 59 percent of normal annual area 

precipitation. 

Climate Division 6 East Central

Climate Division 6 East Central is in east-central Oklahoma. Water Year 2006 was the second driest in the 82 years 

of record from 1925–2006, with 27.70 inches of rainfall, a 

deficit of 15.21 inches or 65 percent of normal area precipitation (table 1). Water Year 1956 was the driest year, from the 

1952–56 drought period, with only 23.86 inches of rainfall, 

a deficit of 19.05 inches or 56 percent of normal annual area 

precipitation.

Climate Division 7 Southwest

Climate Division 7 Southwest is in southwest Oklahoma. 

Water Year 2006 was the third driest in the 82 years of record 

from 1925–2006, with 18.59 inches of rainfall, a deficit of 

8.97 inches or 67 percent of normal area precipitation 

(table 1). Water Year 1956 was the driest year, from the 

1952–56 drought period, with only 17.45 inches of rainfall, 

a deficit of 10.11 inches or 63 percent of normal annual area 

precipitation.

Climate Division 8 South Central

Climate Division 8 South Central is in south-central 

Oklahoma. Water Year 2006 was the third driest in the 

82 years of record from 1925–2006, with 24.45 inches of 

rainfall, a deficit of 12.18 inches or 67 percent of normal area 

precipitation (table 1). Water Year 1956 was the driest year, 

from the 1952–56 drought period, with only 16.46 inches 

of rainfall, a deficit of 20.17 inches or 45 percent of normal 

annual area precipitation.

Climate Division 9 Southeast

Climate Division 9 Southeast is in southeast Oklahoma. 

Water Year 2006 was the sixth driest in the 82 years of record 

from 1925–2006, with 34.89 inches of rainfall, a deficit of 

13.62 inches or 72 percent of normal area precipitation 

(table 1). Water Year 1956 was the driest year, from the 

1952–56 drought period, with only 25.10 inches of rainfall, 

a deficit of 23.41 inches or 52 percent of normal annual area 

precipitation.

Streamflow of Long-Term Sites

Twelve long-term streamflow-gaging sites with periods 

of record ranging from 62 to 78 years were selected to show 

how streamflow deficits varied by region (fig. 9, table 2). Two 

graphs are presented for each long-term site (figs. 10 to 21). 

The first graph is similar to the statewide runoff plot in figure 

4. The annual mean streamflow (U.S. Geological Survey, 

2007b) for each water year of the period of record is plotted as 

a departure bar from the long-term median annual flow (“normal” annual flow, blue line), and a 5-year weighted-average 

departure streamflow is plotted as a red line (A graphs). Wetter 

years plot above the median line and drier years plot below 

the median line. Water Year 2006 then can be compared to the 

dry years from the four previous major hydrologic droughts in 

the 20th century by the depth of bars. The length and severity of the water year 2002–2006 drought period in terms of 

streamflow deficit can be compared to the four previous major 

hydrologic droughts by the 5-year weighted average line.

The second graph shows a comparison of the daily-mean 

flow from Water Year 2006 (red line; U.S. Geological Survey, 

2008d) to the long-term daily mean flow (blue line; U.S. Geological Survey, 2008e) and provides an indication of how the 

streamflow deficits changed seasonally (B graphs).

Table 2 shows how Water Year 2006 streamflow from 

each long-term site compares with the driest year from each 

of the four previous major hydrologic droughts in the 20th 

century, and shows the rank and percent of long-term medianannual flow (“normal”) for each low-flow year. Statewide 

runoff during the driest years also is ranked. Statewide runoff 

in Water Year 2006 was sixth driest in the 82 years of record 

from 1925-2006.

Salt Fork Arkansas River at Tonkawa

Salt Fork Arkansas River at Tonkawa (07151000) is a 

streamflow-gaging site in north-central Oklahoma. Water 

Year 2006 was the sixth driest in the 65 years of record from 

1942–2006, with just 19 percent of normal annual flow 

(table 2). Water Year 1954 was the driest year, from the 

1952–56 drought period, with 12 percent of normal annual 

flow. Zero flow was not recorded during Water Year 2006, 

with some wet periods in November, May, and June (fig. 10). 

The lowest flow was at the end of the water year in August 

and September (fig. 10; appendix 1; U.S. Geological Survey, 

2008c).

Chikaskia River near Blackwell

Chikaskia River near Blackwell (07152000) is a streamflow-gaging site in north-central Oklahoma. Water Year 2006 

was the 15th driest in the 70 years of record from 1937–2006, 

with 45 percent of normal annual flow (table 2). Water Year 

1954 was the driest year, from the 1952–56 drought period, 
Streamflow of Long-Term Sites 15

#

#

#

#

#

#

#

#

#

#

#

#

KANSAS

TEXAS

COLORADO

NEW MEXICO

MISSOURI ARKANSAS

Red

River

Washita

River

Canadian

River

North

Canadian

River

Cimmaron

River

Arkansas

River

Blue River

near Blue

Canadian River

at Calvin

Washita River

near Dickson

Cimarron River

near Ripley

Cimarron River

near Waynoka

Red River atArthur City, Texas

Salt Fork RedRiver at Mangum

Illinois Rivernear Tahlequah

Red River nearGainesville, Texas

Chikaskia River

near Blackwell

North Canadian River

near Wetumka

Salt Fork Arkansas

River at Tonkawa

94°

98°

98°

100°

100°

102°

102° 96°

96°

38°

36°

36°

34°

34°

Station names correspondto table 2

EXPLANATION

#

County Boundary

Rivers

State Boundary Line

Long-term streamflow-gaging stations

Rivers from U.S. Environmental ProtectionAgency River Reach File version 1.Albers Equal-Area Projection.North American Datum 1983.

0 50 100 25 Miles0 50 100 25 Kilometers

A

B

C

D Appendix 5 photograph locations

E F Canadian River: A. near Thomas

B. at BridgeportC. near Union CityD. at PurcellE. near WanetteF. near Ada

Figure 9. Selected long-term streamflow-gaging stations in Oklahoma and Canadian River photograph locations.
16 Hydrologic Drought of Water Year 2006 Compared with 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 previous documented 

hydrologic droughts and the recent hydrologic drought period.

[yr, year; avg, average; Rank, rank of driest year of drought period out of period of record; mi2, square miles; N, nonregulated; R, regulated; WY, water year; 

ft3/s, cubic feet per second; SW, statewide]

Site 

no.

Station

number Station name

Contributing 

drainage

area

(mi2

)

Type of

record

(N/R)

Continuous record 

period of record 

(complete WY)

Years

of

record

Long-term 

annual

median

(ft3

/s)

SW Statewide 1 1925-2006 1 82

1 07151000 Salt Fork Arkansas River at Tonkawa, Okla. 4,520 R 1942-2006 65 808

2 07152000 Chikaskia River near Blackwell, Okla. 1,859 N 1937-2006 70 480

3 07158000 Cimarron River near Waynoka, Okla. 8,504 N 1938-2006 69 231

4 07161450 Cimarron River near Ripley, Okla. 2 13,053 N 1940-2006 67 1,345

5 07196500 Illinois River near Tahlequah, Okla. 959 N 1936-2006 71 919

6 07231500 Canadian River at Calvin, Okla. 23,151 N,R 1939-42, 1945-2006 66 1,376

7 07242000 North Canadian River near Wetumka, Okla. 9,391 R 1938-2006 69 683

8 07300500 Salt Fork Red River at Mangum, Okla. 1,357 N 1938-2006 69 71.8

9 07316000 Red River near Gainesville, Texas 24,846 N,R 1937-2006 70 2,535

10 07331000 Washita River near Dickson, Okla. 7,202 N,R 1929-2006 78 1,400

11 07332500 Blue River near Blue, Okla. 476 N 1937-2006 70 254

12 07335500 Red River at Arthur City, Texas 38,595 R 1945-2006 62 7,223

1

 Ranks from Statewide Annual Runoff Summary USGS Waterwatch web page, U.S. Geological Survey (2007a) Although there is record from continuous 

streamflow gages since WY 1903, there were few operating gages and gaps where no gages were operating prior to 1925.

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
Streamflow of Long-Term Sites 17

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 previous documented 

hydrologic droughts and the recent hydrologic drought period.—Continued

[yr, year; avg, average; Rank, rank of driest year of drought period out of period of record; mi2, square miles; N, nonregulated; R, regulated; WY, water year; 

ft3/s, cubic feet per second; SW, statewide]

Hydrologic Drought Periods

1929-41 3 1952-56 3 1961-72 3 1976-1981 3 2002-2006 2006

Lowest yr / Rank Lowest yr / Rank Lowest yr / Rank Lowest yr / Rank Lowest yr / Rank Rank

Site

no.

Avg

annual

flow 

(ft3

/s)

Percent

longterm 

median

Avg

annual 

flow

(ft3

/s)

Percent 

longterm 

median

Avg

annual

flow

(ft3

/s)

Percent 

longterm 

median

Avg

annual

flow

(ft3

/s)

Percent 

longterm 

median

Avg

annual

flow

(ft3

/s)

Percent 

longterm 

median

Avg 

annual 

flow 

(ft3

/s)

Percent 

longterm 

median

SW 1940 1 1953 2 1964 4 1981 7 2006 6 6

1 NA 1954 1 1964 3 1981 13 2006 6 6

95.5 12% 137 17% 280 35% 157 19% 157 19%

2 1940 4 2 1954 1 1966 4 1981 7 2006 15 15

76.6 16% 71.0 15% 97.6 20% 152 32% 217 45% 217 45%

3 1939 4 26 1956 5 1971 4 1977 17 2002 3 10

174 75% 53.6 23% 46.7 20% 134 58% 46.0 20% 96.1 42%

4 1940 4 4 1953 1 1971 2 1981 11 2006 12 12

307 23% 235 17% 294 22% 455 34% 491 37% 491 37%

5 1940 4 6 1954 1 1964 3 1981 5 2006 8 8

279 30% 193 21% 239 26% 275 30% 289 31% 289 31%

6 1940 4 8 1956 6 1966 3 1981 1 2006 2 2

478 35% 393 29% 217 16% 184 13% 190 14% 190 14%

7 1940 4 2 1956 1 1963 3 1981 5 2006 4 4

157 23% 156 23% 166 24% 178 26% 176 26% 176 26%

8 1940 4 1 1952 4 1971 2 1981 5 2006 3 3

12.3 17% 17.5 24% 12.5 17% 22.7 32% 14.4 20% 14.4 20%

9 1939 4 5 1953 2 1964 3 1983 12 2006 1 1

1,010 40% 651 26% 654 26% 1,274 50% 567 22% 567 22%

10 1939 4 3 1956 5 1964 1 1981 7 2006 2 2

391 28% 441 31% 340 24% 495 35% 384 27% 384 27%

11 1939 4 2 1956 1 1964 9 1980 4 2006 5 5

42.9 17% 30.8 12% 114 45% 77.7 31% 79.5 31% 79.5 31%

12 NA 1952 9 1964 2 1980 3 2006 1 1

4,182 58% 2,754 38% 2,953 41% 1,794 25% 1,794 25%
18 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

A

Hydrologic

Droughts 1952-56 1961-72 1976-81 2002-06

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

Salt Fork Arkansas River at Tonkawa, Okla.

07151000 Regulated 1942-2006

Annual Departure

Median Annual Streamflow 808 ft /s3

5-year - Weighted Average

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Sreamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1942-2006

Salt Fork Arkansas River at Tonkawa, Okla. 07151000

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

Regulated 1942-2006

Streamflow, in cubic feet per second (ft /s) 3 Figure 10. Salt Fork Arkansas River at Tonkawa (A) annual departure from long-term median annual streamflow, water years 

1942–2006 (B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1942–2006.
Streamflow of Long-Term Sites 19

A

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

Chikaskia River near Blackwell, Okla.

07152000 Unregulated 1937-2006

Annual Departure

Median Annual Streamflow 480 ft /s3

5-year Weighted Average

-1,000

-500

0

500

1,000

1,500

2,000

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1937-2006

Chikaskia River near Blackwell, Okla. 07152000

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

Streamflow, in cubic feet per second (ft /s) 3 Figure 11. Chikaskia River near Blackwell (A) annual departure from long-term median annual streamflow, water years 1937–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1937–2006.
20 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

A

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

-500

-250

0

250

500

750

1,000

Cimarron River near Waynoka, Okla.

07158000 Unregulated 1938-2006

Annual Departure

Median Annual Streamflow 231 ft /s3

5-year Weighted Average

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1938-2006

Cimarron River near Waynoka, Okla. 07158000

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

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

Zero

flow

Figure 12. Cimarron River near Waynoka (A) annual departure from long-term median annual streamflow, water years 1938–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1938–2006.
Streamflow of Long-Term Sites 21

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1940-2006

Cimarron River near Ripley, Okla. 07161450

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

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

A

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

6,000

Cimarron River near Ripley, Okla.

07161450 Unregulated 1940-2006

Annual Departure

Median Annual Streamflow 1,345 ft /s3

5-year Weighted Average

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

Figure 13. Cimarron River near Ripley (A) annual departure from long-term median annual streamflow, water years 1940–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1940–2006. Includes 

streamflow record 1940–87 from nearby station 0716100, Cimarron River at Perkins.
22 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

Illinois River near Tahlequah, Okla.

07196500 Unregulated 1936-2006

Annual Departure

Median Annual Streamflow 919 ft /s3

5-year Weighted Average

-1,000

-500

0

500

1,000

1,500

2,000

A

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1936-2006

Illinois River near Tahlequah, Okla. 07196500

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

Streamflow, in cubic feet per second (ft /s) 3 Figure 14. Illinois River near Tahlequah (A) annual departure from long-term median annual streamflow, water years 1936–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1936–2006.
Streamflow of Long-Term Sites 23

A

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

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 1965-2006

Annual Departure

Median Annual Streamflow 1,376 ft /s3

5-year Weighted Average

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1939-42, 1945-2006

Canadian River at Calvin, Okla. 07231500

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

Regulated 1965-2006

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

Zero

flow

Figure 15. Canadian River at Calvin (A) annual departure from long-term median annual streamflow, water years 1939–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1939–2006.
24 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

A

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

-1,000

-500

0

500

1,000

1,500

2,000

North Canadian River near Wetumka, Okla.

07242000 Regulated 1938-2006

Annual Departure

Median Annual Streamflow 683 ft /s3

5-year Weighted Average

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1938-2006

North Canadian River near Wetumka, Okla. 07242000

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

Regulated 1938-2006

Streamflow, in cubic feet per second (ft /s) 3 Figure 16. North Canadian River near Wetumka (A) annual departure from long-term median annual streamflow, water years 

1938–2006 (B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1938–2006.
Streamflow of Long-Term Sites 25

Water Year

-100

100

150

200

250

A

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

-50

0

50

Salt Fork Red River at Mangum, Okla.

07300500 Unregulated 1938-2006

Annual Departure

Median Annual Streamflow 71.8 ft /s3

5-year Weighted Average

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

1

10

100

1,000

10,000

2

3

4

5

7

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1938-2006

Salt Fork Red River at Mangum, Okla. 07300500

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

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

Zero

flow

Figure 17. Salt Fork Red River at Mangum (A) annual departure from long-term median annual streamflow, water years 1938–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1938–2006.
26 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

A

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 1945-2006

Annual Departure

Median Annual Streamflow 2,535 ft /s3

5-year Weighted Average

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1937-2006

Red River near Gainesville, Texas 07316000

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

Regulated 1945-2006

Streamflow, in cubic feet per second (ft3/s) Annual Departure from Median Annual Streamflow

in cubic feet per second (ft3/s)

Figure 18. Red River near Gainesville, Texas, (A) annual departure from long-term median annual streamflow, water years 1937–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1937–2006.
Streamflow of Long-Term Sites 27

with 15 percent of normal annual flow. Zero flow was not 

recorded during Water Year 2006, with some wet periods in 

November, April-May, and August-September (fig. 11). The 

lowest flow was near the end of the water year in July (fig. 11; 

appendix 2; U.S. Geological Survey, 2008c).

Cimarron River near Waynoka

Cimarron River near Waynoka (07158000) is a streamflow-gaging site in northwest Oklahoma. Water Year 2006 

was the 10th driest in the 69 years of record from 1938–2006, 

with 42 percent of normal annual flow (table 2). Water Year 

2002 was the third driest year, from the 2002–2006 drought 

period, with 20 percent of normal annual flow. Zero flow was 

recorded in Water Year 2006 during the first part of August 

(fig. 12). The lowest flow was at the end of the water year in 

first part of August and last part of September (fig. 12; appendix 3; U.S. Geological Survey, 2008c).

Cimarron River near Ripley

Cimarron River near Ripley (07161450) is a streamflowgaging site in central Oklahoma. Water Year 2006 was the 12th

driest in the 67 years of record from 1940–2006, with 

37 percent of normal annual flow (table 2). Water Year 1953 

was the driest year, from the 1952–56 drought period, with 

17 percent of normal annual flow. Zero flow was not recorded 

during Water Year 2006, with some wet periods in October, 

May-July, and August-September (fig. 13). The lowest flow 

was near the end of the water year in August (fig. 13; appendix 

4; U.S. Geological Survey, 2008c).

Illinois River near Tahlequah

Illinois River near Tahlequah (07196500) is a streamflow-gaging site in east-central Oklahoma. Water Year 2006 

was the 8th driest in the 71 years of record from 1936–2006, 

with just 31 percent of normal annual flow (table 2). Water 

Year 1954 was the driest year, from the 1952–56 drought 

period, with 21 percent of normal annual flow. Zero flow was 

not recorded during Water Year 2006, with some wet periods 

in May, August, and September (fig. 14). The lowest flow was 

near the end of the water year in August (fig. 14; U.S. Geological Survey, 2008c).

Canadian River at Calvin

Canadian River at Calvin (07231500) is a streamflowgaging site in east-central Oklahoma. Water Year 2006 was 

the second driest in the 66 years of record from 1939–42, 

1945-2006; with just 14 percent of normal annual flow (table 

2). Water Year 1981 was the driest year, from the 1976-81 

drought period, with 13 percent of normal annual flow. Zero 

flow was recorded in Water Year 2006 during most of the 

month of August with some wet periods in October and March 

through June (fig. 15). The lowest flow was at the end of the 

water year in August and September (fig. 15; U.S. Geological 

Survey, 2008c).

Daniel Fenner of U.S. Fish and Wildlife Service (written commun., 2006) photographically documented no flow 

or little flow during mid-August on the reach of the Canadian 

River near Thomas upstream from the streamflow-gaging site 

at Bridgeport to near Ada, just upstream from the streamflowgaging site at Calvin (fig. 9, appendix 5).

North Canadian River near Wetumka

North Canadian River near Wetumka (07242000) is 

a streamflow-gaging site in central Oklahoma. Water Year 

2006 was the fourth driest in the 69 years of record from 

1938–2006, with just 26 percent of normal annual flow 

(table 2). Water Year 1956 was the driest year, from the 

1952–56 drought period, with 23 percent of normal annual 

flow. Zero flow was not recorded during Water Year 2006, 

with some wet periods in October, March through June and 

September (fig. 16). The lowest flow was near the end of the 

water year in August (fig. 16; U.S. Geological Survey, 2008c).

Salt Fork Red River at Mangum

Salt Fork Red River near Mangum (07300500) is a 

streamflow-gaging site in southwest Oklahoma. Water Year 

2006 was the third driest in the 69 years of record from 

1938–2006, with just 20 percent of normal annual flow 

(table 2). Water Year 1940 was the driest year, from the 

1929–41 drought period, with 17 percent of normal annual 

flow. Zero flow was recorded in Water Year 2006 during 

late June through August, with some wet periods in October, 

March through June and late August and September (fig. 17; 

U.S. Geological Survey, 2008c). Low flow was recorded from 

October through March, and some days in April through September (fig. 17).

Red River near Gainesville, Texas

Red River near Gainesville, Texas, (07316000) is a 

streamflow-gaging site in south-central Oklahoma. Water Year 

2006 was the driest in the 70 years of record from 1937–2006, 

with just 22 percent of normal annual flow (table 2). Water 

Year 1953 was second driest year, from the 1952–56 drought 

period, with 26 percent of normal flow. Zero flow was not 

recorded during Water Year 2006, with some wet periods in 

October, March, May, and September (fig. 18). The lowest 

flow was near the end of the water year in August (fig. 18, 

U.S. Geological Survey, 2008c). 
28 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Washita River near Dickson

Washita River near Dickson (07331000) is a streamflowgaging site in south-central Oklahoma. Water Year 2006 was 

the second driest in the 78 years of record from 1929–2006, 

with just 27 percent of normal annual flow (table 2). Water 

Year 1964 was the driest year, from the 1961–72 drought 

period, with 24 percent of normal annual flow. Zero flow was 

not recorded during Water Year 2006, with some wet periods 

in October, March, May, and September (fig. 19). The lowest 

flow was near the end of the water year in August (fig. 19; 

appendix 6; U.S. Geological Survey, 2008c).

Blue River near Blue

Blue River near Blue (07332500) is a streamflow-gaging 

site in south-central Oklahoma. Water Year 2006 was the fifth 

driest in the 70 years of record from 1937–2006, with just 31 

percent of normal annual flow (table 2). Water Year 1956 was 

the driest year, from the 1952-56 drought period, with 

12 percent of normal annual flow. Zero flow was not recorded 

during Water Year 2006, with some wet periods in March 

through May (fig. 20). The lowest flow was near the end of the 

water year in August and September (fig. 20; U.S. Geological 

Survey, 2008c).

Red River at Arthur City, Texas

Red River at Arthur City, Texas (07335500) is a streamflow-gaging site in southeast Oklahoma. Water Year 2006 was 

the driest in the 62 years of record from 1945–2006, with just 

25 percent of normal annual flow (table 2). Water Year 1964 

was the second driest year, from the 1961–72 drought period, 

with 38 percent of normal annual flow. Zero flow was not 

recorded during Water Year 2006, with some wet periods in 

March through May (fig. 21). The lowest flow was near the 

end of the water year in August and September (fig. 21; U.S. 

Geological Survey, 2008c).

Effects of Low Streamflows

Hydrologic drought is associated with the effects of periods of precipitation deficits on streamflow, lake and reservoir 

levels, and ground water. Although all droughts start with precipitation deficits, hydrologists are more concerned with how 

this deficit affects the hydrologic system. Hydrologic droughts 

commonly lag the 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 on reservoir levels may 

not affect water supply, hydroelectric power production, or 

recreational uses for several months. Water in the hydrologic 

storage systems, 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 increase substantially (National Drought 

Mitigation Center, 2006a).

Conditions at Major Reservoirs

The hydrologic drought of Water Year 2006 substantially 

affected the reservoirs in the state. The effects on 31 selected 

major lakes or reservoirs at three times of the water year are 

presented in table 3 (fig. 22; Oklahoma Water Resources 

Board, 2006b; U.S. Army Corps of Engineers, 2007). Table 3 

shows the conservation storage in these lakes, expressed both 

in terms of volume and percent of conservation storage, on 

October 4, 2006, a few days after the end of the Water Year 

2006. On that day the statewide total conservation storage was 

86.3 percent. Table 3 also compares levels at these reservoirs, 

expressed as percent of conservation storage, on two other 

days: (1) the levels on December 21, 2005, when the statewide 

total conservation storage was lowest, 84.5 percent, and (2) 

May 24, 2006, when the statewide total conservation storage was the highest, 96.8 percent. The north-central region of 

the state consistently had the highest percent of conservation 

storage (or wettest) while the southwest region of the state 

consistently had the lowest percent of conservation storage 

(or driest) at all three times of the water year. Lake Altus at 

Lugert (site 21, fig. 22) in the southwest region was the driest 

reservoir for the entire water year (appendix 7).

Lake Eufaula (site 18, fig. 22) is a good example of the 

dependence several water-use customers have on the reservoirs. Six municipalities, eight rural water districts, a hydroelectric plant, and natural gas plant all use water from the lake 

in addition to recreational use (Jackson, 2006b). However, it 

must be noted that the condition of farm ponds across Oklahoma was more drastically affected than the major reservoirs. 

Hundreds of farm ponds across Oklahoma had completely 

dried up by January 15, 2006 (Jackson, 2006b). 

Hydroelectric Power Generation

Hydroelectric power in Oklahoma was greatly reduced 

during Water Year 2006 because of reduction in available 

streamflow as a result of the hydrologic drought. Table 4 

illustrates the drastic reduction in hydroelectric power generation at selected hydroelectric plants from Calendar Year 2005 

to Water Year 2006. Even though there was a 3-month overlap 

between October through December 2005, the Water Year 

2006 hydroelectric power generation at sites in Oklahoma was 

only 7 to 47 percent of the Calendar Year 2005 power generation (table 4).
Effects of Low Streamflows 29

-2,000

-1,000 A

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

0

1,000

2,000

3,000

4,000

5,000

6,000

Washita River near Dickson, Okla.

07331000 Unregulated 1929-1960

Regulated 1962-2006

Annual Departure

Median Annual Streamflow 1,400 ft /s3

5-year Weighted Average

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1929-2006

Washita River near Dickson, Okla. 07331000

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

Regulated 1962-2006

Streamflow, in cubic feet per second (ft /s) 3 Figure 19. Washita River near Dickson (A) annual departure from long-term median annual streamflow, water years 1929–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1929–2006.
30 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

A

1920 1930 1940 1950 1960 1970 1980 1990 2000 2010

Water Year

-500

-250

0

250

500

750

1,000

Blue River near Blue, Okla.

07332500 Unregulated 1937-2006

Annual Departure

Median Annual Streamflow 254 ft /s3

5-year Weighted Average

Hydrologic

Droughts 1929-41 1952-56 1961-72 1976-81 2002-06

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3

B

10

100

1,000

10,000

100,000

20

30

40

50

70

200

300

400

500

700

2,000

3,000

4,000

5,000

7,000

20,000

30,000

40,000

50,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1937-2006

Blue River near Blue, Okla. 07332500

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

Streamflow, in cubic feet per second (ft /s) 3 Figure 20. Blue River near Blue (A) annual departure from long-term median annual streamflow, water years 1937–2006 (B) comparing 

daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1937–2006.
Effects of Low Streamflows 31

A

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 1945-2006

Annual Departure

Median Annual Stramflow 7,223 ft /s3

5-year Weighted Average

Hydrologic

Droughts 1952-56 1961-72 1976-81 2002-06

Annual Departure from Median Annual Streamflow,

in cubic feet per second (ft /s) 3 100,000

B

100

1,000

10,000

200

300

400

500

600

700

2,000

3,000

4,000

5,000

6,000

7,000

20,000

30,000

40,000

50,000

60,000

70,000

Daily-Mean Streamflow Water Year 2006

Long-Term Daily-Mean Streamflow Water Years 1945-2006

Red River at Arthur City, Texas 07335500

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

Regulated 1945-2006

Streamflow, in cubic feet per second (ft /s) 3 Figure 21. Red River at Arthur City, Texas, (A) annual departure from long-term median annual streamflow, water years 1945–2006 

(B) comparing daily-mean streamflow of Water Year 2006 and long-term daily-mean streamflow, water years 1945–2006.
32 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma KANSASTEXAS COLORADO

NEW MEXICO

MISSOURI ARKANSAS

Red

River

Washita

River

Canadian River

North

Canadian

River

Cimmaron

River

Arkansas

River

Verdigris

River

Neosho River

North

Fork

Red

River

22

20

18

25

7

6

11 3

10 8

2

30

27

19

28

12

26

14

13

9 5

17

24

29

21 31

1

23

4

15

16

94° 96°

96° 98°

98°

100°

100°

102°

102°

38°

36°

36°

34°

34°

EXPLANATION

Numbers at reservoir locationscorrespond to table 3

State Boundary Line

Reservoir StoragePercent of Conservation Storage as of October 4, 2006

<50%51 - 70%71 - 80%81 - 90%91 - 100%County Boundary

Rivers

0 50 100 25 Miles0 50 100 25 Kilometers

Rivers from U.S. Environmental ProtectionAgency River Reach File version 1.Albers Equal-Area Projection.North American Datum 1983.

Figure 22. Locations of selected major lakes and reservoirs in Oklahoma and percent of Conservation Storage as of October 4, 2006.
Effects of Low Streamflows 33

Table 3. Storage in selected major Oklahoma lakes and reservoirs during October 4, 2006, by National Weather Service Climate 

Division, and comparison with December 21, 2005, and May 24, 2006, storage.—Continued

[Shading indicates reservoir storage below 80 percent of total conservation storage; WY, Water Year]

Site

number

(fig. 22)

Climate Division

 Lake or Reservoir

Conservation 

storage 

(acre-feet)

10/04/06

storage

(acre-feet)

Percent of conservation storage

WY end 

10/4/2006 a

WY driest 

12/21/2005 b

WY wettest 

5/24/2006 c

2-North Central

1 Fort Supply 13,900 9,888 71.1 98.6 97.8

2 Great Salt Plains 31,420 25,986 82.7 100.0 98.1

3 Kaw* 375,160 375,160 100.0 100.0 100.0

Regional Totals/Averages 420,480 411,034 97.8 100.0 99.8

3-Northeast

4 Birch 19,225 16,665 86.7 71.1 97.4

5 Copan 34,634 27,817 80.3 75.9 100.0

6 Fort Gibson 365,200 361,087 98.9 98.7 100.0

7 Grand 1,672,000 1,509,910 90.3 88.9 99.6

8 Hudson 200,300 195,802 97.8 83.8 100.0

9 Hulah 22,565 20,240 89.7 66.0 100.0

10 Keystone 512,307 418,770 81.7 78.1 100.0

11 Oologah 552,219 510,351 92.4 88.8 100.0

12 Skiatook 322,700 228,371 70.8 83.9 86.7

Regional Totals/Averages 3,701,150 3,289,013 88.9 87.2 98.6

4-West Central

13 Canton 111,310 74,178 66.6 97.1 100.0

14 Foss 165,480 136,940 82.8 91.6 92.2

Regional Totals/Averages 276,790 211,118 76.3 93.8 95.3

5-Central

15 Arcadia 27,520 27,502 99.9 97.2 100.0

16 Heburn 7,105 5,691 80.1 88.0 100.0

17 Thunderbird 119,600 78,486 65.6 85.4 80.3

Regional Totals/Averages 154,225 111,679 72.4 87.7 84.7

6-East Central

18 Eufaula* 2,314,583 1,967,711 85.0 74.1 92.9

19 Tenkiller 654,100 602,009 92.0 77.7 100.0

Regional Totals/Averages 2,968,683 2,569,720 86.6 74.9 94.4

7-Southwest

20 Fort Cobb 80,010 72,710 90.9 100.0 100.0

21 Altus 132,830 10,508 7.9 37.6 48.8

22 Tom Steed 88,970 40,510 45.5 70.7 61.6
34 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Ground Water at a Long-Term Site

A long-term recording ground-water well that has a close 

hydraulic connection between streams and the aquifer illustrates the effect the Water Year 2006 drought had on groundwater levels in south-central Oklahoma. Figure 23 shows the 

daily ground-water levels in the Fittstown well during Water 

Year 2006 (red line; U.S. Geological Survey, 2007f) compared to the long-term mean-daily water level (blue line; U.S. 

Geological Survey, 2008e). The water level was almost 17 feet 

lower than normal in March; although, late spring rains caused 

a rise in water levels in May. At the end of the water year the 

water level was more than 9 feet lower than normal.

Wildfires

Fire danger was critical because of the drought starting in 

November 2005. Hundreds of homes had been destroyed and 

nearly 600,000 acres were burned by January 2006 (Knapp, 

2006; Slater, 2006). In a 24-hour period starting January 1, 

2006, more than 30 separate fires burned more than 81,000 

acres and more than a dozen homes were lost (Knapp, 2006). 

Governor Brad Henry issued a statewide burn ban in November 2005 that remained in effect, though discontinued several 

times, until the last counties were removed from the ban on 

December 4, 2006.

Summary

Water Year 2006 (October 1, 2005, to September 30, 

2006) was a year of extreme hydrologic drought and the driest year in the recent 2002–2006 drought in Oklahoma. The 

severity of this recent drought can be evaluated by comparing 

it with four previous major hydrologic droughts, water years 

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

The period of water years 1925–2006 was selected as the 

period of record because before 1925 few continuous record 

streamflow-gaging sites existed and gaps existed where no 

streamflow-gaging sites were operated. Statewide annual precipitation in Water Year 2006 was second driest with 

Table 3. Storage in selected major Oklahoma lakes and reservoirs during October 4, 2006, by National Weather Service Climate 

Division, and comparison with December 21, 2005, and May 24, 2006, storage.—Continued

[Shading indicates reservoir storage below 80 percent of total conservation storage; WY, Water Year]

Site

number

(fig. 22)

Climate Division

 Lake or Reservoir

Conservation 

storage 

(acre-feet)

10/04/06

storage

(acre-feet)

Percent of conservation storage

WY end 

10/4/2006 a

WY driest 

12/21/2005 b

WY wettest 

5/24/2006 c

Regional Totals/Averages 301,810 123,728 41.0 63.9 66.1

8-South Central

23 Arbuckle 72,400 63,165 87.2 95.9 100.0

24 McGee Creek 113,930 96,505 84.7 89.6 100.0

25 Texoma* 2,556,122 2,257,985 88.3 92.4 100.0

26 Waurika* 190,200 139,059 73.1 93.3 89.2

Regional Totals/Averages 2,932,652 2,556,714 87.2 92.4 99.3

9- Southeast

27 Broken Bow* 954,175 796,073 83.4 77.5 97.4

28 Hugo* 158,617 158,617 100.0 66.5 100.0

29 Pine Creek* 53,750 53,750 100.0 80.6 100.0

30 Sardis 274,330 252,137 91.9 90.1 100.0

31 Wister 60,162 47,915 79.6 62.6 100.0

Regional Totals/Averages 1,501,034 1,308,492 87.2 78.0 98.4

State Totals 12,256,824 10,581,498 86.3 84.5 96.8

 Reservoirs below 80 percent Storage 8 11 2

*

 indicates seasonal pool operation; actual storage figures/percents may vary

a

 WY end, 10/4/2006, approximates end of WY 2006 State Total Conservation Storage (Oklahoma Water Resources Board, 2006a).

b

 WY driest, 12/21/2005, approximates lowest State Total Conservation Storage for WY 2006 (Oklahoma Water Resources Board, 2005).

c

 WY wettest, 5/24/2006, approximates highest State Total Conservation Storage for WY 2006 (Oklahoma Water Resources Board, 2006b).
Summary 35

72 percent of normal precipitation and statewide annual runoff 

in Water Year 2006 was sixth driest in the 82 years of record. 

Annual area-averaged precipitation totals by the nine 

National Weather Service Climate Divisions from Water Year 

2006 are compared to those during four previous major hydrologic droughts in the 20th century to show how rainfall deficits 

in Oklahoma varied by region. Only two of the nine climate 

divisions, Climate Division 1 Panhandle and Climate Division 

4 West Central, had minor rainfall deficits, with 

85 percent or more of normal precipitation; while the rest of 

the climate divisions had severe rainfall deficits in Water Year 

2006 ranging from only 65 to 73 percent of normal annual 

precipitation. The East Central, Southwest, and South Central 

Climate Divisions were hardest hit with only 65 to 67 percent 

of normal annual precipitation.

Regional streamflow patterns for Water Year 2006 indicate that Oklahoma was part of the regionwide below-normal 

streamflow conditions for Arkansas-White-Red River Basin, 

the sixth driest since 1930. The percentage of long-term stations in Oklahoma (with at least 30 years of record) having 

below-normal streamflow reached 80 to 85 percent for some 

days in August and November 2006.

Twelve long-term streamflow-gaging sites with periods 

of record ranging from 62 to 78 years were selected to show 

how streamflow deficits varied by region. The hydrologic 

drought worsened going from north to south in Oklahoma, 

ranging from 45 percent in the north, to just 14 percent in 

east-central Oklahoma, and 20 percent of normal annual 

streamflow in the southwest. The Chikaskia River near Blackwell and the Cimarron River near Waynoka in north-central 

Oklahoma had 45 and 42 percent of normal annual streamflow 

during Water Year 2006, respectively. The Canadian River 

at Calvin in east-central Oklahoma had only 14 percent of 

normal annual streamflow, the second driest year in 66 years; 

the Salt Fork Red River near Mangum in southwest Oklahoma 

had only 20 percent of normal annual streamflow, the third 

driest in the 69 years of record and the Red River near Gainesville in south-central Oklahoma had only 22 percent of normal 

annual streamflow, the driest year in 70 years.

Some effects of low streamflows during Water Year 

2006 include (1) major reservoirs had only 86.3 percent of 

Table 4. Comparison of hydroelectric power generation at selected Oklahoma hydroelectric plants between Calendar Year 

2005 and Water Year 2006.

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

Site 

number

(fig.22)

Lake

hydroelectric

generation project

Climate division

Calendar Year 

2005

power

(GWh)

Water Year 2006

Power

(GWh)

Percent of

CY 2005

power

3 Kaw 1 2-North Central 130 36 28

6 Fort Gibson 2 3-Northeast 231 46 20

7 Grand (Pensacola) 3 3-Northeast 452 101 22

8 Hudson (RS Kerr) 3 3-Northeast 235 40 17

8 Salina 3, 4 3-Northeast 276 130 47

10 Keystone 2 3-Northeast 310 113 36

18 Eufaula 2 6-East Central 192 13 7

19 Tenkiller 2 6-East Central 95 21 22

27 Broken Bow 2 9-Southeast 98 29 30

1

 Data from Oklahoma Municipal Power Authority (OMPA) Calendar Year 2005 data from R. Morecroft (OMPA, written commun., 2008). Water 

Year 2006 data from D. Osburn (OMPA, written commun., 2008).

2

 Data from Department of Energy, Southwestern Power Administration (SWPA), Calendar Year 2005 data from J. Croton (SWPA, written commun., 2007), and Water Year 2006 data from Southwestern Power Administration (2007).

3

 Data from Grand River Dam Authority (GRDA). All data from A. Bishop (GRDA, written commun., 2007)

4

 Salina Pumped Storage Project, Chimney Rock Reservoir. Water used on the Salina Creek Arm of Lake Hudson, classified as offstream project.
36 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

the statewide conservation storage available at the end of 

the water year, (2) hydroelectric power generation at sites 

in Oklahoma was only 7 to 47 percent of the Calendar Year 

2005 power generation, (3) ground water at a long-term site in 

south-central Oklahoma had a drop in water level of more than 

17 feet lower than normal, and (4) wildfires burned more than 

600,000 acres.

Selected References

Bisbee, Julie, 2006, Lack of rain forces producers to sell 

cattle: The Oklahoman, July 11, 2006, accessed March 6, 

2008, at http://www.newsok.com/article/keyword/2000621/

Blazs, R.L., Walters, D.M., Coffey, T.E., Boyle, D.L., and 

Wellman, J.J., 2007, Water resources data, Oklahoma, water 

year 2006: U.S. Geological Survey Water-Data Report 

OK-06-1, 394 p.

Cole-Frowe, Carol, 2007, Water puzzle − State struggles with 

uneven water supply: Enid News, November 28, 2007, 

accessed December 12, 2007 at http://www.enidnews.

com/waterstories/local_story_332113854.html/resources_

printstory

Egan, Timothy, 2006, The worst hard time: New York, Houghton Mifflin Company, 340 p. 

Hoyt, J.C., 1936, Droughts of 1930-34: U.S. Geological Survey Water Supply Paper 680, 106 p. 

Hoyt, J.C., 1938, Drought of 1936: U.S. Geological Survey 

Water Supply Paper 820, 62 p. 

Holmes, R.R., Jr., 2008, Drought − Perceptions, effects, and 

assessment: U.S. Geological Survey, 3 p., accessed February 6, 2008, at http://il.water.usgs.gov/hydro_conditions/

drought_intro.html

Daily water level, feet below land surface

125

120

115

110

105

100

95

90

Fittstown Ground-Water Well

01N-06E-04 CAD 1

Daily Water Level Water Year 2006

Long-Term Mean Daily Water Level Water Years 1981-2006

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

Figure 23. Fittstown ground-water well, comparing daily water levels for Water Year 2006 and long-term mean-daily water levels, 

water years 1981–2006.
Selected References 37

Hutchison, M.A., 2000, Several Oklahoma cities remain flush 

with plentiful water sources: The Oklahoman, July 24, 

2000, accessed July 25, 2000, at http://www.oklahoman.

com/cgi-in/shart?ID=520839&TP=getarticle

Jackson, Ron, 2006a, Farmers, ranchers feeling drain of persistent drought conditions: The Oklahoman, July 11, 2006, 

accessed March 6, 2008, at http://www.newsok.com/article/

keyword/2000620/

Jackson, Ron, 2006b, When will the rain come?: The 

Oklahoman, January 15, 2006, accessed March 10, 

2008, at http://olive.newsok.com/APA26136/PrintArt.

asp?SkinFolder=Oklahoman

Jian, Xiaodong, Wolock, D.M., and Lins, H.F., 2007, Streamflow of 2006, water year summary: U.S. Geological Survey, 

accessed January 10, 2008, at http://water.usgs.gov/waterwa

tch/2006summary/#regional

Johnson, Cullen, 1956, City to buy land for lake: The 

Oklahoman, December 19, 1956, accessed March 11, 

2008, at http://olive.newsok.com/APA26136/PrintArt.

asp?SkinFolder=Oklahoman

Knapp, Adam, 2006, Oklahoma under burn ban as wild fires 

rage across state: About.com, March 16, 2006, accessed 

March 6, 2008, at http://www.newsok.com/article/

keyword/1788696/

McNutt, Michael, 2006a, Ag department declares state a 

natural disaster area: The Oklahoman, March 16, 2006, 

accessed March 6, 2008, at http://www.newsok.com/article/

keyword/1788696/

McNutt, Michael, 2006b, Gov. issues statewide burn ban: The 

Oklahoman, August 2, 2006, accessed March 6, 2008, at 

http://www.newsok.com/article/keyword/2824513/

McNutt, Michael, 2006c, Burn ban lifted for some: The 

Oklahoman, September 13, 2006, accessed March 31, 

2008, at http://olive.newsok.com/APA26136/PrintArt.

asp?SkinFolder=Oklahoman

Nace, R.L. and Pluhowski, E.J., 1965, Drought of 1950’s with 

special reference to the Midcontinent: U.S. Geological 

Survey Water Supply Paper 1804, 88 p. 

National Agricultural Statistics Service, 2007, Oklahoma 

agricultural statistics 2007: National Agricultural Statistics 

Service, 107 p.

National Climatic Data Center, 2007a, Statewide monthly total 

precipitation data, Calendar Year 1895–2006, file drd964x.

pcpst.txt: National Climatic Data Center, accessed May 9, 

2007, at http://www1.ncdc.noaa.gov/pub/data/cirs/ drd964x.

pcpst.txt

National Climatic Data Center, 2007b, State Climate Division 

monthly total precipitation data, Calendar Year 1895–2006, 

file drd964x.pcp.txt: National Climatic Data Center, 

accessed May 9, 2007, at http://www1.ncdc.noaa.gov/pub/

data/cirs/drd964x.pcp.txt

National Climatic Data Center, 2007c, Climate of 2006, 

annual review U.S. drought, January 11, 2007: National 

Climatic Data Center, accessed May 9, 2007, at http://www.

ncdc.noaa.gov/oa/climate/research/2006/ann/droughtsummary.html

National Drought Mitigation Center, 2006a, What is drought? 

– Understanding and defining drought: National Drought 

Mitigation Center, accessed September 13, 2006, at http://

www.drought.unl.edu/whatis/concept.htm

National Drought Mitigation Center, 2006b, What is drought? 

– Drought in the dust bowl years: National Drought Mitigation Center, accessed September 13, 2006, at http://www.

drought.unl.edu/whatis/dustbowl.htm

National Drought Mitigation Center, 2007, U.S. Drought 

Monitor: National Drought Mitigation Center, accessed 

December 21, 2007, at http://www.drought.unl.edu/dm/

monitor.html

Oklahoma Climatological Survey, 2005, Oklahoma Climate 

- Winter 2005-2006: Oklahoma Climatological Survey, 

accessed January 18, 2008, at http://climate.mesonet.org/

seasonal_summary.html

Oklahoma Climatological Survey, 2006a, Oklahoma Climate 

- Spring 2006: Oklahoma Climatological Survey, accessed 

January 18, 2008, at http://climate.mesonet.org/seasonal_

summary.html

Oklahoma Climatological Survey, 2006b, Oklahoma Climate - 

Summer 2006: Oklahoma Climatological Survey, accessed 

January 18, 2008, at http://climate.mesonet.org/seasonal_

summary.html

Oklahoma Climatological Survey, 2006c, Oklahoma Climate 

- Fall 2006: Oklahoma Climatological Survey, accessed 

January 18, 2008, at http://climate.mesonet.org/seasonal_

summary.html

Oklahoma Climatological Survey, 2008a, Percentage of 

normal rainfall, water year 2006: Oklahoma Climatological Survey, accessed January 16, 2008, at http://climate.

mesonet.org/rainfall/2006waterpct.gif

Oklahoma Climatological Survey, 2008b, Departure from normal rainfall, inches, water year 2006: Oklahoma Climatological Survey, accessed January 16, 2008, at http://climate.

mesonet.org/rainfall/2006waterdel.gif

Oklahoma Climatological Survey, 2008c, Drought Monitoring 

Tools: Oklahoma Climatological Survey, accessed January 

18, 2008, at http://climate.mesonet.org/rainfall_update.html
38 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Oklahoma Water Resources Board, 2005, Oklahoma Water 

Resources Bulletin and summary of current conditions, 

December 21, 2005: Oklahoma Water Resources Board, 

accessed October 5, 2006, at http://www.owrb.ok.gov/

supply/drought/pdf_dro/2005/189_1221_2005.pdf

Oklahoma Water Resources Board, 2006a, Oklahoma Water 

Resources Bulletin and summary of current conditions, 

October 4, 2006: Oklahoma Water Resources Board, 

accessed October 5, 2006, at http://www.owrb.ok.gov/

supply/drought/pdf_dro/2006/209_1004_2006.pdf

Oklahoma Water Resources Board, 2006b, Oklahoma Water 

Resources Bulletin and summary of current conditions, 

May 24, 2006: Oklahoma Water Resources Board, accessed 

October 5, 2006, at http://www.owrb.ok.gov/supply/drought/

pdf_dro/2006/200_0524_2006.pdf

Oklahoma Water Resources Board, 2007a, Hydrologic drought 

of Water Year 2006 – A historical context: Oklahoma Water 

Resources Board, 4 p.

Slater, Grant, 2006, How DRY can it get?: The Oklahoman, 

July 2, 2006,accessed March 6, 2008 at http://www.newsok.

com/article/keyword/1882166/

Southwestern Power Administration, 2007, 2004-2006 Annual 

report: Southwestern Power Administration, accessed 

October 17, 2008, at http://www.swpa.gov/PDFs/SWPA_

FY2004-2006_annual_report.pdf

Sutter, J. D., 2006, Drought continues to wither state: The 

Oklahoman, September 3, 2006.

Tortorelli, R.L., 2002, Statistical summaries of streamflow in 

Oklahoma through 1999: U.S. Geological Survey WaterResources Investigations Report 02–4025, 510 p.

Tortorelli, R.L., Cooter, E.J., and Schuelein, J.W., 1991, Oklahoma – Floods and droughts, in U.S. Geological Survey, 

National water summary 1988-1989 – Hydrologic events 

and floods and droughts: U.S. Geological Survey WaterSupply Paper 2375, p. 451–458.

U.S. Army Corps of Engineers, 2007, Tulsa district water control home page: U.S. Army Corps of Engineers, accessed 

March 13, 2007, at http://www.swt-wc.usace.army.mil/

U.S. Geological Survey, 2007a, Water watch − Past streamflow conditions – Table of computed median runoff (mm/

day), by water-year, for Oklahoma: U.S. Geological Survey, accessed January 11, 2007, at http://water.usgs.gov/

waterwatch/?m=statesum&r=ok

U.S. Geological Survey, 2007b, Automated data processing 

system (ADAPS), Daily Values Monthly and Annual Statistics (DVMAS): U.S. Geological Survey.

U.S. Geological Survey, 2007c, Drought watch — USGS 

Streamflow information on drought: U.S. Geological Survey, accessed November 27, 2007, at http://water.usgs.gov/

waterwatch/?m=pa07d_dry&r=ok&w=pa07a_dry%2Cplot

U.S. Geological Survey, 2007d, National Water Information 

System, web interface, USGS surface-water daily data for 

Oklahoma: U.S. Geological Survey, accessed November 27, 

2007, at http://waterdata.usgs.gov/ok/nwis/dv/?referred_

module=sw

U.S. Geological Survey, 2007e, Automated data processing 

system (ADAPS), Daily Values Daily Summary Statistics 

(DVDAYSTAT): U.S. Geological Survey.

U.S. Geological Survey, 2007f, National Water Information 

System, web interface, USGS ground-water daily data for 

Oklahoma: U.S. Geological Survey, accessed November 27, 

2007, at http://waterdata.usgs.gov/ok/nwis/dv/?referred_

module=gw

U.S. Geological Survey, 2008a, Streamflow of 2006 

– Water Year Summary: U.S. Geological Survey, 

accessed January 10, 2008, at http://water.usgs.gov/

waterwatch/2006summary/

U.S. Geological Survey, 2008b, U.S. Geological Survey 

Photographic Library, Oklahoma: U.S. Geological Survey, accessed February 22, 2008, at http://libraryphoto.

cr.usgs.gov/cgi-bin/search.cgi?search_mode=noPunct; 

free_form=Oklahoma;free_form=;free_form=;free_

form=;start=50

U.S. Geological Survey, 2008c, Water-resources data for the 

United States, Water Year 2006: U.S. Geological Survey, 

accessed March 6, 2008, at http://wdr.water.usgs.gov/

wy2006/search.jsp

U.S. Geological Survey, 2008d, National Water Information 

System, web interface, USGS ground-water-level daily 

statistics for Oklahoma: U.S. Geological Survey, accessed 

October 20, 2008, at http://waterdata.usgs.gov/ok/nwis/

dvstat/?referred_module=gw

Vance, Brian, ed., 2007, Oklahoma water atlas: Oklahoma 

Water Resources Board, 190 p.
Appendixes 39

Appendixes
40 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma
Appendixes 41

07151000 Salt Fork Arkansas River at Tonkawa August 6, 2006

Appendix 1. Salt Fork of Arkansas River at Tonkawa (0751000), showing low flow, 30 cubic feet per second, looking upstream 

from U.S. Highway 77 bridge, August 6, 2006. Photographer: Jim Norvell, USGS.

07152000 Chikaskia River near Blackwell August 6, 2006

Appendix 2. Chikaskia River near Blackwell (07152000), showing low flow, 74 cubic feet per second, looking downstream from 

State Highway 11 bridge, August 6, 2006. Photographer: Jim Norvell, USGS.
42 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

07158000 Cimarron River near Waynoka August 9, 2006

Appendix 3. Cimarron River near Waynoka (07158000), showing low flow, 0.17 cubic foot per second, looking downstream from 

U.S. Highway 281 bridge, August 9, 2006. Photographer: Marty Phillips, USGS.

07161450 Cimarron River near Ripley August 11, 2006

Appendix 4. Cimarron River near Ripley (07161450), showing low flow, 55 cubic feet per second, looking upstream toward 

State Highway 33 bridge, August 11, 2006. Photographer: Marty Phillips, USGS.
Appendixes 43

samohTraenreviRnaidanaC 6002,11tsuguA

A

07228500 Canadian River at Bridgeport August 11, 2006

B

Appendix 5. Canadian River upstream to downstream, August 11, 2006: (A) near Thomas, showing no flow, looking upstream from 

State Highway 33 bridge (B) at Bridgeport (07228500), showing low flow and pools, 2.9 cubic feet per second, looking upstream from 

U.S. Highway 281 bridge. All photographs: David Fenner, USFWS, and locations are shown on fig. 9. —Continued
44 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

Canadian River near Union City August 11, 2006

C

07229200 Canadian River at Purcell August 11, 2006

D

Appendix 5. Canadian River upstream to downstream, August 11, 2006: (C) near Union City, showing no flow and pools, looking 

upstream from State Highway 81 bridge (D) at Purcell (07229200), showing low flow and pools, 4.2 cubic feet per second, looking 

upstream from U.S. Highway 77 bridge. All photographs: David Fenner, USFWS, and locations are shown on fig. 9. —Continued
Appendixes 45

ettenaWraenreviRnaidanaC 6002,11tsuguA

E

adAraenreviRnaidanaC 6002,61tsuguA

F

Appendix 5. Canadian River upstream to downstream: (E) near Wanette, showing no flow, looking upstream from State Highway 

102 bridge, August 11, 2006 (F) near Ada, showing no flow, looking downstream from State Highway 99 bridge, August 16, 2006. All 

photographs: David Fenner, USFWS, and locations are shown on fig. 9.
46 Hydrologic Drought of Water Year 2006 Compared with Four Major Drought Periods of the 20th Century in Oklahoma

07331000 Washita River near Dickson August 22, 2006

Appendix 6. Washita River near Dickson (07331000), showing low flow and pools, 5.7 cubic feet per second, looking downstream 

from U.S. Highway 177 bridge, August 22, 2006. Photographer: Ernest Smith, USGS.

sutlAekaL 6002,22tsuguA

Appendix 7. Lake Altus at Lugert (07302500), showing very low lake elevation, 7.7 percent of conservation storage, looking 

upstream from dam, August 22, 2006. Photographer: Martin Schneider, USGS.
Back Cover: Picture of children in the Sam Noble Oklahoma Museum of Natural History summer program walking on Lake Thunderbird’s shoreline, Cleveland County, Oklahoma, published July 2, 2006. Photographer: Steve 

Sisney. Copyright 2006, The Oklahoma Publishing Company.

Publishing support provided by:

Lafayette Publishing Service Center

For more information concerning this publication, contact:

Director, USGS Oklahoma Water Science Center

202 NW 66th St., Bldg. 7

Oklahoma City, OK 73116

(405) 810-4400

Or visit the Oklahoma Water Science Center Web site at:

http://ok.water.usgs.gov
Tortorelli, R.L.—Hydrologic Drought of Water Year 2006 Compared with Major Drought Periods in Oklahoma—Scientific Investigations Report 2008–5199

Children walking on the shoreline of Lake Thunderbird. Photograph by Steve Sisney. Copyright 2006, The Oklahoma Publishing Company.

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