Drought: Looking Back and Planning Ahead
Todd H. Votteler, Ph.D. Executive Manager of Science,
Intergovernmental Relations and Policy Guadalupe-Blanco River Authority
What is Drought? It Depends . . . Research in the 1980s uncovered more than 150 published definitions of drought. All drought definitions originate from a deficiency of precipitation or meteorological drought but other types of drought and impacts cascade from this deficiency. The four major definitions are based on basic approaches to measuring drought: n Meteorological Drought n Agricultural Drought n Hydrological Drought n Socioeconomic Drought
Meteorological Drought
Meteorological drought is defined usually on the basis of the degree of dryness and the duration of the dry period. Definitions of meteorological drought are region specific since the atmospheric conditions are variable regionally.
Agricultural Drought
Agricultural drought links various characteristics of meteorological (or hydrological) drought to agricultural impacts, focusing on precipitation shortages, differences between actual and potential evapotranspiration, soil water deficits, reduced groundwater or reservoir levels, etc.
Hydrological Drought
Hydrological drought is associated with the effects of periods of precipitation (including snowfall) shortfalls on surface or subsurface water supply (i.e., streamflow, reservoir and lake levels, groundwater). The frequency and severity of hydrological drought is often defined on a watershed or river basin scale.
Socioeconomic Drought
Socioeconomic drought associates the supply and demand of some economic good with elements of meteorological, hydrological, and agricultural drought. Socioeconomic drought occurs when the demand for an economic good exceeds supply as a result of a weather-related shortfall in water supply.
Current Conditions and the 2011 Drought
L
S
L
L
L
L
SL
SL
SL
SL
SL
SL
SL
SLSL
SLSL
SL
U.S. Drought Monitor August 21, 2012Valid 7 a.m. EDT
The Drought Monitor focuses on broad-scale conditions.Local conditions may vary. See accompanying text summaryfor forecast statements. Released Thursday, August 23, 2012
Author: Michael Brewer/Liz Love-Brotak, NOAA/NESDIS/NCDC
L
S
Intensity:D0 Abnormally DryD1 Drought - ModerateD2 Drought - SevereD3 Drought - ExtremeD4 Drought - Exceptional
http://droughtmonitor.unl.edu/
Drought Impact Types:
S = Short-Term, typically <6 months(e.g. agriculture, grasslands)
L = Long-Term, typically >6 months(e.g. hydrology, ecology)
Delineates dominant impacts
H
A
A
AA
H
A
H
A
A
H
A
A
A
A
H
A
H
H
A
AH
AH
AH
AH
AH
U.S. Drought MonitorH
August 30, 2011Valid 8 a.m. EDT
The Drought Monitor focuses on broad-scale conditions.Local conditions may vary. See accompanying text summaryfor forecast statements. Released Thursday, September 1, 2011Authors: Eric Luebehusen, U.S. Department of Agriculture
A
AH
Intensity:D0 Abnormally Dry
D1 Drought - Moderate
D2 Drought - Severe
D3 Drought - Extreme
D4 Drought - Exceptional
http://drought.unl.edu/dm
Drought Impact Types:A = Agricultural (crops, pastures,
grasslands)
H = Hydrological (water)
Delineates dominant impacts
U.S. Drought Monitor
http://droughtmonitor.unl.edu
Intensity:D0 Abnormally Dry
D1 Drought - Moderate
D2 Drought - Severe
D3 Drought - Extreme
D4 Drought - Exceptional
Drought Conditions (Percent Area)
Texas
August 21, 2012Valid 7 a.m. EST
The Drought Monitor focuses on broad-scale conditions.Local conditions may vary. See accompanying text summaryfor forecast statements.
Michael Brewer, National Climatic Data Center, NOAAReleased Thursday, August 23, 2012
None D0-D4 D1-D4 D2-D4 D3-D4 D4
Current
Last Week(08/14/2012 map)
3 Months Ago(05/22/2012 map)
Start ofCalendar Year(12/27/2011 map)
Start ofWater Year
(09/27/2011 map)
One Year Ago(08/16/2011 map)
0.07 99.93 99.72 98.36 92.78 74.50
0.00 100.00 100.00 99.16 96.65 85.75
0.01 99.99 97.83 84.81 67.32 32.36
9.00 91.00 57.92 33.55 13.54 1.15
11.08 88.92 78.72 44.03 12.59 0.82
11.75 88.25 73.61 38.48 14.08 1.18
U.S. Drought Monitor
http://drought.unl.edu/dm
Intensity:D0 Abnormally Dry
D1 Drought - Moderate
D2 Drought - Severe
D3 Drought - Extreme
D4 Drought - Exceptional
Drought Conditions (Percent Area)
Texas
August 30, 2011Valid 7 a.m. EST
The Drought Monitor focuses on broad-scale conditions.Local conditions may vary. See accompanying text summaryfor forecast statements.
Eric Luebehusen, USDAReleased Thursday, September 1, 2011
None D0-D4 D1-D4 D2-D4 D3-D4 D4
Current
Last Week(08/23/2011 map)
3 Months Ago(05/31/2011 map)
Start ofCalendar Year(12/28/2010 map)
Start ofWater Year
(09/28/2010 map)
One Year Ago(08/24/2010 map)
75.51 24.49 5.52 0.68 0.00 0.00
75.57 24.43 2.43 0.99 0.00 0.00
7.89 92.11 69.43 37.46 9.59 0.00
2.25 97.75 96.07 91.89 81.09 50.65
0.00 100.00 99.93 99.01 94.42 77.80
0.00 100.00 99.92 99.01 95.04 81.08
Current Texas Reservoir Storage
!! "#$%&!!!!!!! !!!'%(#)!!!!!!!!!!!!!!!!*+,-.(.+,&!!!!!!!!!!!!!!!!!!!!!!!!!!/#0+)(!!
Telephone (512) 463-7847 Fax (512) 936-0816 1-800-RELAYTX (for the hearing impaired) www.twdb.texas.gov
!
PO BOX 13231 1700 N. Congress Avenue Austin, TX 78711-3231
CONSERVATION STORAGE DATA FOR SELECTED MAJOR TEXAS RESERVOIRS
Figures are based on the end of the month data at 109 major reservoirs that represent 96 percent of the total conservation storage capacity of the 175 major water supply reservoirs in Texas. Major reservoirs are defined as having a conservation storage capacity of 5,000 acre-feet or greater.
RESERVOIR STORAGE July 2012
At the end of the month water supply reservoirs was at 22.75 million acre-feet*, or 73% of their total conservation storage capacity. This is 709,000 acre-feet less than a month ago but 1.3 million acre-feet more than storage at this time last year. Only one reservoir, Lake Houston, held 100% of conservation storage capacity. Eleven reservoirs were at or below 10% full: E.V. Spence, O. C. Fisher, Twin Buttes, Hords Creek Lake, J. B. Thomas, ; Electra and Meredith were effectively empty, Palo Duro at 4%, Mackenzie, Red Bluff, White River were at 8%, 9% and 10% full, respectively. Total combined storage was greater than 70% in the North Central (86%), East (92%), and Upper Coast (100%) regions. The regions with the lowest percentage storage were the High Plains (1%) and Trans-Pecos regions (9%). Storage over the last month declined in 7 regions and increased in 2 regions. Elephant Butte reservoir held 179,000 acre-feet, or 9% of storage capacity. This is 94,000 acre-ft less than a month ago. * Only the Texas share of storage in border reservoirs is counted.
Cond
ition
s In July total storage in 109 of the state’s major water supply reservoirs was 23 million acft*, or 73% of total conservation storage capacity.
Source: TWDB
Impacts of the 2011 Drought
n High Plains Underground Water Conservation District No. 1 experienced a 2.56 ft decline in the Ogallala Aquifer district wide in 2011.
n Edwards Aquifer 2011 recharge was 112,000 acft vs average recharge is 712,000 acft. It was only 43,700 acft in 1956!
n Texas agricultural losses due to the 2011 drought reached a record $7.62 billion.
n Texas Water Journal publishing John Nielsen-Gammon's "The 2011 Texas Drought”
The 2012 Drought Continues
n Combined storage of Highland Lakes is 45%. n San Antonio Pool of Edwards Aquifer in
Stage 3 Drought, Uvalde Pool in Stage 4 Drought.
n Lake Meredith, Twin Buttes, Electra, O.C. Fisher are all at less than 1% storage!!!
14
Will El Niño Save Us?
Summary
* Note: These statements are updated once a month in association with the ENSO Diagnostics Discussion: http://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory
ENSO Alert System Status: El Niño Watch*
ENSO-neutral conditions continue.* Equatorial sea surface temperatures (SST) are greater than 0.5 C above average
across the eastern Pacific Ocean. The atmospheric circulation over the tropical Pacific is near average. El Niño conditions are likely to develop during August or September 2012.*
Pacific Niño 3.4 SST Outlook
Figure provided by the International Research Institute (IRI) for Climate and Society (updated 16 Aug 2012).
Nearly all of the dynamical models predict a transition from ENSO-neutral conditions (Niño-3.4 SST anomalies between -0.5 C and +0.5 C) to El Niño during the Northern Hemisphere summer/fall, with El Niño continuing into winter 2012-13. The average dynamical model forecast is warmer than the statistical models.
The seasonal outlooks combine the effects of long-term trends, soil moisture, and, when appropriate, ENSO.
Temperature Precipitation
U. S. Seasonal Outlooks September November 2012
Drought Over the Last 500 Years
Tree-Ring Study n Report published 2011 in Texas Water Journal. n Tree rings can be used as proxies for climate. n Baldcypress used to reconstruct climate,
precipitation, & streamflow. n Accurate dating matching patterns of wide (wet
year) & narrow (dry year) rings. n Oldest tree, 582 years, was a sapling in 1426. n 1947-1957 DOR most severe multi-year drought
since records 1895 n 1700s & 1800s multiple droughts exceed DOR.
Texas Baldcypress
Rec
onst
ruct
ed D
iv. 7
Ju
ne P
DSI
!
How Have Our Surface & Groundwater Supplies Changed?
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
2020
Acre
-feet
per
Per
son
0.0
0.5
1.0
1.5
2.0
2.5
3.0
3.5
4.0
1953
Source: NRS
Source: NRS
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
2020
Milli
ons
of A
cre-
feet
0
10
20
30
40
50
60
Milli
ons
of P
eopl
e
0
5
10
15
20
25
30
Total water level declines in the major aquifers through 2005
Source: TWDB
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5.2.3 GROUNDWATER SUPPLY TRENDS89"' :$);0!<%("$' %=%./%5./.(4' 0;-5"$&' "&(%5/.&9"!'
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.0'("$-&')2'3"$#"0('#9%0:"'2$)-'(9"'6++>'?(%("'@%("$'
FIGURE 5.7. PROJECTED EXISTING GROUNDWATER SUPPLIES AND GROUNDWATER AVAILABILITY THOUGH 2060 (ACRE-FEET PER YEAR).
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5.2.4 POTENTIAL FUTURE IMPACTS RELATING TO GROUNDWATER AVAILABILITY
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5.7
8,073,609
7,201,7786,597,213
6,115,2485,848,663 5,688,293
13,329,824
12,386,342
11,593,135
10,907,61910,474,786
10,137,361
0
2,000,000
4,000,000
6,000,000
8,000,000
10,000,000
12,000,000
14,000,000
2010 2020 2030 2040 2050 2060
SupplyAvailability
Source: TWDB
Final Thoughts n 2011 Drought has not ended in the western half
of Texas as hydrologic drought persists. n Droughts more severe and of longer duration
than the Drought of Record have occurred and will reoccur in Texas at some point.
n The era of water supply creation ended in the 1980s & was replaced by the current era of water reallocation. Reallocation is shifting water from agricultural to municipal & industrial uses.
n Per capita surface & groundwater supplies are steadily declining in Texas. 28
Thank you.
