Climate change related to floods, droughts, and water supply shortages in the Capital Area Raymond Slade, Jr. Certified Professional Hydrologist

Slide show organization IntroductionIntroduction Floods in the Capital AreaFloods in the Capital Area Current and previous droughtsCurrent and previous droughts Current and future water supplyCurrent and future water supply shortages during severe drought shortages during severe drought

Do we understand water resources ?

“The scientific literature and the Intergovernmental Panel on Climate Change (IPCC) have independently suggested that the intensity and frequency of extreme weather events will increase due to climate change.” American Meteorological Society Introduction It is likely that the Capital Area will experience higher and more frequent floods, and droughts with greater intensity and duration. Arguably, Central Texas, has the greatest variability in precipitation and runoff (extreme floods and severe droughts).

Google “Texas flood”… Floods in the Capital Area

You might get Stevie Ray Vaughn playing the song “Texas flood”

Texas leads the Nation in flood fatalities and flood damage costs Flood fatalities by State Flood insurance damage costs by State

Hallettsville, Fayette County 22.7 inches of rain, June 29-30, 1940 Also in Fayette County: 14.9 inches of rain May 22-28, inches of rain Oct , 1981

San Marcos, Hays County 30 inches of rain, Oct 17-18, inches of rain May 14-15, inches of rain in 4 hours and 12 inches in one hour May 11-12, 1972 Also in Hays county: 15 inches of rain May 24-31, 1929

Pedernales River near Johnson City, Blanco County 26 inches of rain on Sept 9-11, 1952 Hwy 281

Taylor, Williamson County 38 inches of rain, Sept 10, 1921

Sept 9-10, 1921 storm and flood 38.2 in. during 24 hrs at a U.S. Weather Bureau station at Thrall, Tx (national record) 215 drownings statewide--deadliest flood in Texas history. 87 people drowned in and near Taylor and 93 in Williamson County.

Colorado River at Austin, 1935 “Floods are merely a hazard… mankind is the disaster” Gilbert White Gilbert White Floods in 1936 and 1938 also topped Congress Avenue bridge

Austin, Texas, 1981 Memorial Day flood 13 people drowned, $36 million damages 8 inches rainfall in 2 hours—largest rain depths fell outside Austin. At the time of this flood, at least 7,000 families were known to live within 100-year flood plains in Austin—most did not know. Shoal Creek near 12th Street Flooded area in blue Flooded area superimposed on aerial photo of part of Shoal Creek basin Press release after flood

Current and previous droughts Google “drought”…

You might get a TV meteorologist defining drought as an annual rainfall deficit Father Guido Sarducci Vatican Weatherman, SNL

Typical drought cycle

Palmer Drought Severity Index Increasing numbers represent greater drought intensity Green—wetter than normal Gold – drier than normal Edwards Plateau Through Sept. 2013

Historical drought severity documentation Severe droughts

Public water supply systems under water use restrictions In 10-county Capital Area (Sept 11, 2013) 145 systems under restrictions These systems serve 1,684,000 people

Reality—how we deal with drought Start here

Drought Impacts Economic Development Agricultural Production Electric Power Generation Increased Wildfire Threat Ecological Integrity Public Water Supply From Maidment

Current and future water supply shortages during severe drought

Texas Water Plan 2012 Texas Water Development Board Purpose of Plan Estimate current and future water needs (shortages) and identify water management strategies and associated costs to meet future needs. Based on Data and analyses of current and future population, water use, and water availability (every 10 years from 2010 to 2060) Severe drought conditions (water demand at maximum and supply at minimum) 6 water use types: i.e., municipal (urban & rural), irrigation, livestock, manufacturing, mining, and steam electric)

Existing water supplies - the amount of water that can be produced with current permits, current contracts, and existing infrastructure during severe drought. Water Demand Projections - Quantity of water projected to meet the overall necessities of an area in a specific future year. Water supply needs (shortage) - projected water demands in excess of existing supplies that would be legally and physically available during a severe record. Water management strategies - projects and associated amount of water designed to meet needs for additional water supplies during drought. Definitions of water category terms in the Texas Water Plan

Capital Area population projections ,830, ,322, ,799, ,303, ,809, ,277,000 Year Population 2012 Texas Water Plan Texas Water Development Board

Capital Area municipal water demand, supply, and needs Demand SupplyNeed (shortage) Storage of Lake Austin Demand minus Supply = Need Need

Municipal (urban and rural) water needs, 2020 Burnet Llano Blanco Williamson Travis Hays Lee Bastrop Caldwell Fayette Explanation Need - acre feet per year Percent that demand exceeds supply Number of water suppliers with needs Total for area: Need 37,011 ac-ft per year Demand exceeds supply by 65% 43 water suppliers with needs % % % % % % 3 11, % % 0 0% 0 16,795 52% 4 Total need is 1.8 times the storage in Lake Austin

Municipal (urban and rural) water needs, 2060 Burnet Llano Blanco Williamson Travis Hays Lee Bastrop Caldwell Fayette Explanation Need - acre feet per year Percent that demand exceeds supply Number of water suppliers with needs 13, % 2 Total for area: Need 223,433 ac-ft per year Demand exceeds supply by 65% 66 water suppliers with needs Total need is 10 times the storage in Lake Austin % % 1 0 0% 0 35, % % % 4 69,352 25% 18 76, % % 9

“The scientific literature and the Intergovernmental Panel on Climate Change (IPCC) have independently suggested that the intensity and frequency of extreme weather events will increase due to climate change.” American Meteorological Society Conclusion Arguably, Texas, especially central Texas, already has the greatest variability in precipitation and runoff (extreme floods and severe droughts). Therefore, climate change may increase the frequency and severity of catastrophic floods, and the intensity and duration of severe droughts.