1. Drought:
Looking Back and
Planning Ahead
Todd H. Votteler, Ph.D.
Executive Manager of Science,
Intergovernmental Relations and Policy
Guadalupe-Blanco River Authority

2. 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

3. 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.

4. 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.

5. 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.

6. 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.

7. Current Conditions and
the 2011 Drought

8. U.S. Drought Monitor August 21, 2012
Valid 7 a.m. EDT
L S
SL
SL SL
SL
SL
SL SL
SL
SL
SL
L SL
L
L L
S
SL
Intensity: Drought Impact Types: L
D0 Abnormally Dry Delineates dominant impacts
D1 Drought - Moderate
S = Short-Term, typically <6 months
D2 Drought - Severe (e.g. agriculture, grasslands)
D3 Drought - Extreme
L = Long-Term, typically >6 months
D4 Drought - Exceptional (e.g. hydrology, ecology)
The Drought Monitor focuses on broad-scale conditions.
Local conditions may vary. See accompanying text summary
for forecast statements. Released Thursday, August 23, 2012
http://droughtmonitor.unl.edu/ Author: Michael Brewer/Liz Love-Brotak, NOAA/NESDIS/NCDC

9. U.S. Drought Monitor August 30, 2011
Valid 8 a.m. EDT
AH
H A
A A H
A H
A
H
A A
A
A A
A
A H
AH AH A
AH
AH
A H
AH H
Intensity: Drought Impact Types: H
D0 Abnormally Dry Delineates dominant impacts
D1 Drought - Moderate A = Agricultural (crops, pastures,
D2 Drought - Severe grasslands)
D3 Drought - Extreme H = Hydrological (water)
D4 Drought - Exceptional
The Drought Monitor focuses on broad-scale conditions.
Local conditions may vary. See accompanying text summary
for forecast statements. Released Thursday, September 1, 2011
http://drought.unl.edu/dm Authors: Eric Luebehusen, U.S. Department of Agriculture

10. U.S. Drought Monitor August 21, 2012
Valid 7 a.m. EST
Texas
Drought Conditions (Percent Area)
None D0-D4 D1-D4 D2-D4 D3-D4 D4
Current 11.75 88.25 73.61 38.48 14.08 1.18
Last Week
11.08 88.92 78.72 44.03 12.59 0.82
(08/14/2012 map)
3 Months Ago
9.00 91.00 57.92 33.55 13.54 1.15
(05/22/2012 map)
Start of
Calendar Year 0.01 99.99 97.83 84.81 67.32 32.36
(12/27/2011 map)
Start of
Water Year 0.00 100.00 100.00 99.16 96.65 85.75
(09/27/2011 map)
One Year Ago
0.07 99.93 99.72 98.36 92.78 74.50
(08/16/2011 map)
Intensity:
D0 Abnormally Dry D3 Drought - Extreme
D1 Drought - Moderate D4 Drought - Exceptional
D2 Drought - Severe
The Drought Monitor focuses on broad-scale conditions.
Local conditions may vary. See accompanying text summary
for forecast statements.
Released Thursday, August 23, 2012
http://droughtmonitor.unl.edu Michael Brewer, National Climatic Data Center, NOAA

11. U.S. Drought Monitor August 30, 2011
Valid 7 a.m. EST
Texas
Drought Conditions (Percent Area)
None D0-D4 D1-D4 D2-D4 D3-D4 D4
Current 0.00 100.00 99.92 99.01 95.04 81.08
Last Week
0.00 100.00 99.93 99.01 94.42 77.80
(08/23/2011 map)
3 Months Ago
2.25 97.75 96.07 91.89 81.09 50.65
(05/31/2011 map)
Start of
Calendar Year 7.89 92.11 69.43 37.46 9.59 0.00
(12/28/2010 map)
Start of
Water Year 75.57 24.43 2.43 0.99 0.00 0.00
(09/28/2010 map)
One Year Ago
75.51 24.49 5.52 0.68 0.00 0.00
(08/24/2010 map)
Intensity:
D0 Abnormally Dry D3 Drought - Extreme
D1 Drought - Moderate D4 Drought - Exceptional
D2 Drought - Severe
The Drought Monitor focuses on broad-scale conditions.
Local conditions may vary. See accompanying text summary
for forecast statements.
Released Thursday, September 1, 2011
http://drought.unl.edu/dm Eric Luebehusen, USDA

12. Total combined storage was greater than 70% in the North Central (86%), East (92%), and Upper Coast (100%)
Conditions
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.
Current Texas Reservoir Storage
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 .
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.
CONSERVATI ON STORAGE DATA FOR
SELECTED M AJOR TEXAS RESERVOI RS
PO BOX 13231 1700 N. Congress Avenue Austin, TX 78711-3231
Figures are based on the end of the month data at 109 major reservoirs that represent 96 percent of the total
Source: TWDB
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.

13. 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”

14. 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

15. Will El Niño Save Us?

16. Summary
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.*
* 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

17. Pacific Niño 3.4 SST Outlook
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.
Figure provided by the
International Research
Institute (IRI) for Climate
and Society (updated 16
Aug 2012).

18. U. S. Seasonal Outlooks
September November 2012
Temperature Precipitation
The seasonal outlooks combine the effects of long-term trends,
soil moisture, and, when appropriate, ENSO.

19. Drought Over the Last 500 Years

20. 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.

21. Texas Baldcypress

22. Reconstructed Div. 7
June PDSI
!

23. How Have Our Surface &
Groundwater Supplies Changed?

24. 
4.0
3.5
3.0
Acre-feet per Person
2.5
2.0
1.5
1.0
0.5
0.0
00
10
20
30
40
50
60
70
80
90
00
10
20
19
19
19
19
19
19
19
19
19
19
20
20
20
1953
Source: NRS

25. 
60 30
Millions of Acre-feet 50 25
Millions of People
40 20
30 15
20 10
10 5
0 0
0 0 0 0 0 0 0 0 0 0 0 0 0
1 90 191 192 193 194 195 196 197 198 199 200 201 202
Source: NRS

26. Total water level
declines in the
major aquifers
through 2005
Source: TWDB

27. FIGURE 5.7. PROJECTED EXISTING GROUNDWATER SUPPLIES AND GROUNDWATER AVAILABILITY
THOUGH 2060 (ACRE-FEET PER YEAR).
14,000,000 13,329,824
Supply
12,386,342 Availability
12,000,000 11,593,135
10,907,619
10,474,786
10,137,361
10,000,000
8,073,609
8,000,000 7,201,778
6,597,213
6,115,248
5,848,663 5,688,293
6,000,000
4,000,000
2,000,000
0
2010 2020 2030 2040 2050 2060
.0#$"%&"')$'!"#$"%&"')2'/"&&'(9%0'*+'3"$#"0(')2'(9"'6++>'
!"#$"%&"&'()'*+,*'-.//.)0'%#$"12""('3"$'4"%$'54'6+7+,' ?(%("'@%("$'A/%0':$);0!<%("$'%=%./%5./.(4,
Source: TWDB
5.2.3 GROUNDWATER SUPPLY TRENDS 5.2.4 POTENTIAL FUTURE IMPACTS RELATING TO

28. 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

29. Thank you.