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 than150 published definitions of drought. Alldrought definitions originate from a deficiency ofprecipitation or meteorological drought but othertypes of drought and impacts cascade from thisdeficiency. The four major definitions are basedon basic approaches to measuring drought:n Meteorological Droughtn Agricultural Droughtn Hydrological Droughtn Socioeconomic Drought
Meteorological DroughtMeteorological drought is defined usually on thebasis of the degree of dryness and the durationof the dry period. Definitions of meteorologicaldrought are region specific since theatmospheric conditions are variable regionally.
Agricultural DroughtAgricultural drought links various characteristicsof meteorological (or hydrological) drought toagricultural impacts, focusing on precipitationshortages, differences between actual andpotential evapotranspiration, soil water deficits,reduced groundwater or reservoir levels, etc.
Hydrological DroughtHydrological drought is associated with theeffects of periods of precipitation (includingsnowfall) shortfalls on surface or subsurfacewater supply (i.e., streamflow, reservoir andlake levels, groundwater). The frequency andseverity of hydrological drought is often definedon a watershed or river basin scale.
Socioeconomic DroughtSocioeconomic drought associates the supplyand demand of some economic good withelements of meteorological, hydrological, andagricultural drought. Socioeconomic droughtoccurs when the demand for an economic goodexceeds supply as a result of a weather-relatedshortfall in water supply.
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 SLIntensity: 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 summaryfor forecast statements. Released Thursday, August 23, 2012http://droughtmonitor.unl.edu/ Author: Michael Brewer/Liz Love-Brotak, NOAA/NESDIS/NCDC
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 HIntensity: 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 - ExceptionalThe Drought Monitor focuses on broad-scale conditions.Local conditions may vary. See accompanying text summaryfor forecast statements. Released Thursday, September 1, 2011 http://drought.unl.edu/dm Authors: Eric Luebehusen, U.S. Department of Agriculture
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 - SevereThe Drought Monitor focuses on broad-scale conditions.Local conditions may vary. See accompanying text summaryfor forecast statements. Released Thursday, August 23, 2012http://droughtmonitor.unl.edu Michael Brewer, National Climatic Data Center, NOAA
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 - SevereThe Drought Monitor focuses on broad-scale conditions.Local conditions may vary. See accompanying text summaryfor forecast statements. Released Thursday, September 1, 2011http://drought.unl.edu/dm Eric Luebehusen, USDA
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.
Impacts of the 2011 Droughtn 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- Gammons "The 2011 Texas Drought”
The 2012 Drought Continuesn 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
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
Pacific Niño 3.4 SST Outlook Nearly all of the dynamical models predict a transition from ENSO-neutral conditions (Niño-3.4SST anomalies between -0.5 C and +0.5 C) to El Niño during the Northern Hemispheresummer/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).
U. S. Seasonal Outlooks September November 2012 Temperature PrecipitationThe seasonal outlooks combine the effects of long-term trends,soil moisture, and, when appropriate, ENSO.
Tree-Ring Studyn 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 1895n 1700s & 1800s multiple droughts exceed DOR.
Final Thoughtsn 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