Key Points adapted from the Fourth National Climate Assessment; Chapter 23

The Southern Great Plains

Kansas, Oklahoma, and Texas—collectively known as the Southern Great Plains—experience dramatic and consequential weather events every year. Hurricanes, flooding, severe storms with large hail and tornadoes, blizzards, ice storms, relentless winds, heat waves, cold snaps, and drought threaten the region’s people and economies with some of the most diverse and extreme weather hazards on the planet. These events cause significant stress to existing infrastructure and socioeconomic systems, and they often result in significant loss of life and cost billions of dollars in damages.

Climate conditions vary dramatically across the region: precipitation ranges from an annual average of less than 10 inches in the western portions to over 60 inches in the southeastern corner. Surface water availability varies as a result, with large reservoirs in eastern parts of the region and few reservoirs in the west. Most rivers in the region do not draw from mountain snowpack so their flows depend on seasonal rainfall amounts. The region is vulnerable to periods of drought as well as periods of abundant precipitation. The region has experienced an increase in annual average temperature of 1°–2°F since the early 20th century, with the greatest warming during the winter months.

The Southern Great Plains Region encompasses Kansas, Oklahoma, and Texas.

With the Gulf of Mexico to its southeast, the coastal Southern Great Plains is vulnerable to hurricanes and sea level rise. An extreme storm surge in Galveston Bay would threaten much of the U.S. petroleum and natural gas refining capacity. Variations in freshwater flows and evaporation affect the salinity of bays and estuaries along the coast and have the potential to alter coastal ecosystems and affect the fishing industry. Tropical cyclones are also responsible for exceptional rainfall rates in the region. Houston, Texas, in particular, has experienced several record-breaking floods. Learn about Hurricane Harvey »

The Southern Great Plains is a critical thoroughfare for rail and road freight. It also supports numerous ocean and river ports, and is a major energy producer and exporter. The three-state region accounts for a surprising 25% of all U.S. energy production, and more than 550,000 miles of roads connect the region’s communities and support its economies. The vast and dispersed nature of the region’s infrastructure makes maintaining the region’s aging infrastructure difficult. Infrastructure is typically designed to withstand historical climate extremes and is exposed to the environment year-round. Therefore, as the intensity and frequency of climate-related extremes such as heat, drought, flooding, and severe storms increase, impacts to the region are usually adverse and costly. The Southern Great Plains ranks near the top of states with structurally deficient or functionally obsolete bridges, with some bridges nearing the end of their design life.

The region has tens of thousands of dams and levees with an average age exceeding 40 years, and many of these are not subject to regular inspection and maintenance. Most state and local budgets are unable to meet the funding needs for infrastructure improvements, particularly in rural towns where funding is largely derived from municipal revenue. In urban centers, population growth will likely require expansion of transportation infrastructure and services and revisions to flood control structures and policies. These will likely result in increased water resource needs and a growth in building demand.

Understanding the potential for future changes in the frequency and severity of weather events and their impacts will ultimately determine the sustainability of economies, cultures, ecosystems, health, and life in the region. Over the past two decades, state and local governments have invested in the creation of weather monitoring networks—called Mesonets—that are designed to measure important weather and climate parameters. Mesonet stations are critical infrastructure required to establish the long-term climate record for the region. Observations from these networks have been critical for predicting and preparing for extreme weather events such as droughts, floods, ice storms, and severe convective storms. Data gathered through these networks are used daily by decision-makers, public safety officials, educational institutions, the agricultural sector, and researchers, generating societal and economic benefits that greatly exceed the investments made in Mesonet systems.

Future Climate Conditions

Global climate models indicate a continued increase in average temperatures for the region. By late in the 21st century, if no reductions in emissions take place, the region is projected to experience an additional 30–60 days per year above 100°F than it does now.        

Under both lower- and higher-scenario climate change projections, the number of days exceeding 100°F is projected to increase markedly across the Southern Great Plains by the end of the century. Maps show projected conditions in 2070–2099 as compared to 1976–2005.

Additional insights from climate projections include: 

• The frequency, duration, and intensity of extreme heat events is expected to increase. Conversely, the occurrence of extreme cold events is expected to decrease.
• How climate change might alter patterns of severe weather typically associated with the Southern Great Plains is difficult to quantify. Whatever changes occur are unlikely to be uniform across the region, and additional research is needed.
• Along the Texas coastline, sea levels have risen 5–17 inches over the last 100 years, depending on local topography and  the sinking of land (a process called subsidence). Sea level rise is projected to continue, and will exacerbate risks and impacts from storm surges.
• The frequency and intensity of heavy precipitation are projected to continue to increase in the region, particularly if global emissions of heat-trapping gases continue to grow.
• The expected increase of precipitation intensity implies fewer soaking rains and more time to dry out between events, resulting in lower soil moisture. As increased temperature conditions increase evapotranspiration, the region could experience drier conditions than it has experienced over the past 1,000 years.

Changing demands for food, energy, and water

The quality of life of the 34 million people residing in the Southern Great Plains is dependent upon available resources and natural systems for food, energy, and water. 

• Water is used in every aspect of agricultural production and to generate electricity. 
• Energy is required to extract and deliver water for human and agricultural uses, including wastewater treatment. 
• Both water and energy are required to irrigate and process agricultural products and livestock to feed the region’s increasing population. 

At least 60% of the region’s population is clustered around urban centers and the remaining population is spread across vast areas of rural land. Rapid urbanization and economic development are among the forces driving increases in demand for food, energy, and water in the region’s cities. States in the Southern Great Plains import over 20% of their food-related items from Arizona, and relationships with Mexico also impact the food–energy–water nexus in the region.

Major products from the Southern Great Plains include crops, beef, and petroleum. These three represent just a portion of the interdependencies among food, energy, and water in the region.

Impacts of Drought

When severe drought affects the Southern Great Plains, contention over the availability of water can arise among various industries and sectors. For instance, the regional drought from 2010 to 2015 severely affected both agricultural and aquatic ecosystems, and limited water availability in 2011 limited some power plants’ capacities. Another notable impact of the drought was a reduction of irrigation water released for the Texas Rice Belt farmers on the Texas coastal plains. When facing drought, regional agencies are called to work together to balance competing water demands in an attempt to meet the basic needs of cities, businesses, and industries.

Drought in the Southern Great Plains begins as a physical phenomenon that expands through society. For example, in one year, Matagorda County, Texas, planted acres of rice dropped from 22,000 acres to 2,100 acres. The ripple effect on the local economy was severe, with a 70% decline in sales of farm implements and machinery, and some family-owned establishments that had survived for decades closed permanently. Irrigation strategies shifted from river-based sources to pumping water from the Gulf Coast Aquifer and this resulted in dozens of new wells being drilled. Pumping of groundwater from the increased number of wells then resulted in declining groundwater levels, adding stress to water levels that were already falling in the region.. Some farmers attempted to adapt by making the difficult transition to other crops such as corn. However, when flooding rains inundated the region in 2016, 15% of the corn crop was destroyed by flood waters. Thus the 2010–2015 drought simultaneously affected agriculture, energy, recreation, and economic activity, eventually leading to increased groundwater use. 

Water for the Future

• Projected increases in the population of Texas are estimated to contribute to a 17% increase in water demand over the next 50 years. This estimate accounts for growing demand for municipal use, manufacturing, and power generation.
• Water use projections in Oklahoma are expected to increase by 21% for municipal use, 22% for agricultural use, and 63% for energy use. 
• The Kansas Water Plan’s preliminary assessment of projected water demand also shows an increase of 20%, but with the expected variability depending upon rural versus urban areas.

The importance of groundwater as a resource in the region will increase under a changing climate. Throughout much of western Kansas, western Oklahoma, and the Texas Panhandle, groundwater from the Ogallala Aquifer is the dominant water source, and it is used primarily for agriculture. The aquifer is known to be shrinking faster than it is replenishing, and some portions are likely to become partially or completely depleted within the next 25 years. If extensive periods of drought occur, they could trigger large social and economic consequences in the region.

Research into the food–energy–water nexus is in its early stages. It is clear that tradeoffs and complexities exist between sectors, and changes in one sector are likely to affect the entire system. Significant gaps still remain in the scientific understanding of the role climate change will play as a disruptive force and a threat to food, energy, and water security.

Changing conditions threaten current infrastructure

As global temperatures increase, the region is experiencing higher average temperatures year-round, and the number of days per year with maximum temperatures above 100°F is projected to increase markedly. Longer, hotter summers will strain cooling systems and energy utilities, damage road surfaces, and reduce water resources. As warmer temperatures increase evaporation, moisture in the air increases, and heat stress will increase for humans, animals, and plants, especially during the summertime. Population growth, increased urban density, and expansion are expected to intensify the urban heat island effect in many Southern Great Plains cities, resulting in higher energy use for cooling. Any events that result in prolonged power failure during high heat conditions will have a substantial impact on human health and comfort.

Increased aridity or dryness is also projected for the Southern Great Plains with warming, in part due to the increased “thirst” of the atmosphere that depletes soil moisture. In the past, drought conditions have decreased the availability of surface water from rivers and reservoirs, leading to an increase in the use of groundwater. By 2060, the Texas Water Development Board projects that municipal water use will increase to 41% of available supply after accounting for only 9% in 2010. Therefore, a record drought occurring in the 2060s could result in as much as half of the state’s population facing a water supply shortage. Additionally, water infrastructure can be damaged by drought as clay soils that are common throughout the Southern Great Plains shrink. Soil shrinkage can damage both surface and subsurface infrastructure, including roads, water and sewer lines, and building foundations. 

Weather whiplash 

Periods of abundant precipitation followed by drought and high temperatures—a pattern sometimes referred to as weather whiplash—are also linked to increased wildfire activity. The sequence of abundant rain followed by a period of drought leads to abundant fuels that are dry and ready to burn. During the drought of 2011, Texas experienced several major wildfires, including the Bastrop Fire that destroyed more than 1,500 homes. In 2016 and 2017, fires in Kansas and Oklahoma burned more than 400,000 acres and were among the largest in the region’s history. These events killed thousands of cattle, contributed to several human fatalities, and damaged, displaced, or isolated rural communities. Model simulations indicate that wildfire risk will increase throughout the region as temperatures rise, particularly in the summer, and the duration of the fire season increases.

Water levels at Lake Whitney, near Waco, Texas, dropped substantially due to drought during 2011. Water was so low that it exposed dead trees and a reddish, sandy shoreline. 

Following the abrupt end to the persistent drought in 2015, the region suffered extensive damage associated with river and flash flooding. More than 40 inches of precipitation arrived in multiple episodes of very heavy rain in south-central Oklahoma in the spring of 2015. Numerous state and U.S highways experienced regional detours or closures, and a rockslide on Interstate Highway 35 closed portions of the road for several weeks. Flooding in Oklahoma and Texas caused an estimated $2.6 billion in damage in 2015, with $1 million in emergency relief funds provided by the U.S. Department of Transportation’s Federal Highway Administration to assist in the repair of damaged roads. The increasing frequency of extreme precipitation projected by climate models is anticipated to increase vulnerability of existing highway infrastructure.

Changing precipitation frequency and increases in the magnitude and frequency of heavy precipitation will place more stress on existing water resource infrastructure. The region has a large number of older dams and levees: between 1982 and 2012, 82 dams failed in Texas. As climate conditions continue to change, rare events such as 100-year floods (those that currently have a 1% chance of occurring in any given year) are likely to become more common. Extreme events may make flooding worse, and wear and tear on existing flood control infrastructure will necessitate revisions to design standards for flood infrastructure. Floodplain management and mitigation of flooding are currently left largely to local governments and cities and are thus reliant on local funding and resources for successful implementation.

The energy industry is taking climate and extreme weather events into consideration as it invests in renewable energy, distributed generation, smart grid technologies, and storage operations. From 2008 to 2013, the amount of electricity generated from wind more than tripled and the amount from solar has increased more than tenfold. Energy companies are working to ensure that these sources are safe, flexible, and affordable.

Coastal concerns

Rising sea levels and damaging storm surge are leaving some coastal regions vulnerable to climate change. Since the early 20th century, some areas of the Texas coast have experienced sea level rise rates higher than the global average, due in part to extraction of fossil fuels and groundwater, which results in land subsidence. Within Texas alone, 1,000 square miles of land is within 5 feet of the high tide line, including the homes of around 45,000 people. Sensitive assets include 1,600 miles of roadway, several hospitals and schools, 4 power plants, and 254 sites that store hazardous waste or sewage. 

The coastline in the vicinity of Galveston and Texas City is a critical oil refining and transport hub. Sea level rise will affect numerous assets there, including residential communities, roads, waterways, and energy generation facilities. Disruption to coastal oil-refining facilities can cause cascading failures throughout the region, including fuel shortages and higher prices. Rising seas are also a contributing cause of saltwater intrusion into the Gulf Coast Aquifer, a source that provides water for an estimated 8 million people. 

Water

Due to the historical frequency of drought, many municipalities are encouraging water conservation activities. Common strategies include rainwater harvesting, improved residential water-use efficiency, water audits, and restricted water use in times of drought. Other measures involve wastewater treatment and reuse, aquifer storage and recovery, and desalination.

The process of removing salt from water—called desalination—is an important contributor to efforts to meet current and projected water needs for communities, industry, and agriculture in Texas.

Climate threats to the built environment

Some components of the Southern Great Plains’ built environment are vulnerable to increasing temperature, extreme precipitation, and continued sea level rise, particularly as infrastructure ages and populations shift to urban centers. Along the Texas Gulf Coast, sea level rise puts coastal infrastructure at risk. Regional adaptation efforts that harden or relocate critical infrastructure are one option to reduce the risk of climate change impacts.

Changing conditions are likely to require updating of transportation design standards in the region. For example, minimum and maximum temperature ratings for binders used in asphalt roads may need to be modified to improve durability. Bridges may need modifications to meet the demands of higher summer temperatures, calculations of potential flooding will need to be updated to ensure the safety of dams and neighborhoods, and rail speeds may need to be restricted during high temperatures. Many technological solutions exist or are in development to build resilience to these climate-related challenges. However, climate and non-climate stressors and budgetary challenges will continue to present notable challenges to adaptive capacity in the Southern Great Plains.

Predictive analyses studies estimate that climate change and coastal development will cause hurricane damage to increase faster than the U.S. economy is expected to grow. The number of people expected to face substantial damage from coastal storms is estimated to increase more than eightfold over the next 60 years. Although economic analyses for specific regions, sectors, and states in the Southern Great Plains are limited, active ongoing research is beginning to produce critical metrics regarding the socioeconomic impacts of climate change at regional scales.

The role of economics is increasingly recognized as being critical for advancing the resilience of households, businesses, and local governments. Establishing economic resilience in a local business or a regional economy requires the ability to anticipate risk, evaluate how that risk can impact key economic assets, and build a responsive adaptive capacity. At the regional or community level, economic development practitioners can build capacity for economic resilience.

Ecosystems

The Southern Great Plains encompasses diverse ecoregions from high plains to coastal prairies. The region commonly experiences periods of drought punctuated by heavy rainfall events. Researchers have documented an increase in this pattern, and it is affecting water availability and influencing aquatic habitats including lakes, rivers, and streams. 

Species Distribution and Habitats

Climate plays a key role in the distribution of species. As temperatures increase, some species tend to shift to areas with more favorable conditions. Rising temperatures are resulting in changes to the timing and length of growing seasons and migration patterns of birds and butterflies. From Texas, white-wing doves have been expanding northward, and they are now common across Oklahoma. Factors such as habitat loss also influence species distributions, so it is difficult to pinpoint changing climate conditions as a single cause for these distribution changes.

Typical brown speckled back of the Houston toad.

The effects of aridification (a gradual change to a drier climate) will likely have negative impacts on some species. Ecosystem services—the materials and processes that ecosystems produce that benefit people—will also be affected. In general, drought forces wildlife to travel farther to locate food, water, and shelter, leaving them more vulnerable to other stresses. The highly endangered Houston toad was negatively impacted during the 2011 drought and devastating wildfire in Bastrop County, Texas. Whooping crane numbers, which depend on sufficient freshwater inflows for a reliable food source, were also reduced as a result of the drought.

Aridification diminishes the ability for species to thrive if they cannot move to better conditions. Migratory birds are often able to move to areas with better habitat conditions. Loss of irrigated rice fields in Texas contributed to significant declines in wintering waterfowl along the Gulf Coast. Playa lakes in the High Plains serve as important habitat for migrating waterfowl, but these can disappear during drought.
Climate change may be one factor in plant community changes. In turn, these changes affect fish and wildlife. In the Southern Great Plains region, winters are getting warmer and spring is arriving earlier. Along the Texas coast, black mangroves are expanding northward along the coast, and red mangroves, formerly not found in Texas, are now appearing there. 

Aquatic Ecosystems

Higher water temperatures in lakes, wetlands, rivers, and estuaries can result in lower dissolved oxygen, leading to more fish kills. Impacts to reservoirs include fluctuating lake levels, loss of habitat, loss of recreational access, increase in harmful algal blooms, and disconnectedness from upstream and downstream riverine habitats. Researchers have seen local declines in fish populations in rivers due to lack of water or water confined to increasingly narrow pools. Aridification can also have negative impacts on freshwater mussel populations.

Coastal Areas, Bays, and Estuaries

The Texas coast, with 6.5 million people contributing over $37 billion to the region's economy, benefits from bays and estuaries that serve as storm barriers to protect coastal infrastructure. The area also benefits from ecosystem services such as fishing, ecotourism, and the ocean economy. The region’s coastal ecosystems provide protection not only for people, but also for 25% of the Nation's refining capacity, including four crucial ports, much of the strategic petroleum reserves, and strategic military deployment and distribution installations.

Rising seas are impacting beaches along the Texas coast where the average rate of beach erosion is almost 10 feet per year. Sea level rise also means more frequent and longer-lasting flooding of marshes; if they are permanently flooded, protective marshes may become open water. Higher tides and storm surges cause inundation of freshwater areas and beach erosion, leading to a potential decrease or loss of barrier islands and coastal habitats, including nesting habitats and submerged habitat such as seagrass beds. A significant percentage of fishery species in the Gulf of Mexico are dependent upon estuaries for some portion of their life cycle.

Bay waters along the Texas coast have been warming for at least 35 years, more so from warmer winters than warmer summers. The increase in water temperature directly affects water quality, increasing the potential for low levels of dissolved oxygen, or hypoxia. Hypoxic events and harmful algal blooms have caused fish kills, resulting in lower productivity and diversity of estuarine ecosystems. Rivers flowing into coastal estuaries bring important nutrients and sediments that help maintain productive estuarine ecosystems. Reduced inflows of surface and groundwater from the Southern Great Plains have led to dramatic changes of the aquatic and wetland communities in inland locations as well as the coastal ecosystem. Changes in salinity, nutrients, and sediment have impacted oysters and other sensitive estuarine species. In addition, harmful algal blooms have become more frequent, more intense, and more widespread.  

Reduced freshwater inflows during 2011 led to record high salinities in Texas estuaries that contributed to a coast-wide “red tide” harmful algal bloom event. Red tides, a type of harmful algal bloom, most commonly occur during drought years, as the organism that causes red tide does not tolerate low salinity. Red tide blooms cause fish kills and contaminate oysters. In addition, oysters and other shellfish can accumulate red tide toxins in their tissues. People who eat oysters or other shellfish containing red tide toxins become seriously ill with neurotoxic shellfish poisoning. Once a red tide appears to be over, toxins can remain in the oysters for weeks to months. The 2011 bloom started in September and lasted into 2012. Fish mortality was abnormally high and the commercial oyster season was closed.

Human Health

Extreme heat can have significant impacts on healthy individuals in the Southern Great Plains and it acts as a threat multiplier to the medically vulnerable. For instance, heat stress is strongly correlated with complications of lung disease such as asthma and emphysema. Additionally, increases in summer temperature are correlated with increases in the death rate for older individuals with chronic conditions. During the hot summer of 2011, the average temperature in Texas from June to August broke all previous single-month records. Studies also revealed a 3.6% increase in emergency room visits and a 0.6% increase in deaths. Within the Southern Great Plains, changes in extreme temperatures are projected to result in an additional 1,300 deaths per year by the end of the century if emissions of heat-trapping gases continue increasing. If emissions decrease substantially, more than half of these additional deaths could be avoided. 

Populations of mosquitoes, ticks, rodents, and fleas that transmit a variety of human diseases may increase in the Southern Great Plains with rising temperatures and precipitation. Historically, extreme low temperatures in winter controlled insect populations. Now, higher temperatures let insects such as mosquitoes—and the diseases they carry—thrive longer and reproduce more successfully at higher latitudes and altitudes. 

Drought conditions reduce the number of sources and overall quantity of water for both humans and animals. As they share a reduced supply, germ transmission and outbreaks of infectious disease between humans and animals become more likely. Several waterborne diseases have been linked to drought. Skin infections, such as scabies and impetigo, and eye infections, including conjunctivitis, are also correlated with drought.Droughts, floods, and higher temperatures give invasive species a chance to proliferate, and these can harm crops and livestock. Additionally, the nutritional value of some crops are reduced as carbon dioxide levels increase.

Extreme temperatures pose serious health risks to outdoor agricultural workers. By the end of the century, if emissions of heat-trapping gases continue increasing, temperature extremes are projected to result in the loss of about two billion hours of labor across the nation. And the Southern Great Plains region is projected to experience higher-than-average impacts. Many states are developing plans and enhancing healthcare infrastructure to monitor climate-sensitive infectious diseases. Incorporating short-term to seasonal forecasts into public health activities can also help protect people as temperatures increase. Although there is some momentum to adopt adaptation strategies to improve health outcomes, large-scale efforts are still lacking and regional planners may learn from activities ongoing outside the region.

Indigenous Peoples

Water resource constraints, extreme weather events, higher temperature, and other public health issues conspire to increase the climate vulnerabilities of Tribal and Indigenous communities in the Southern Great Plains. Efforts to build community resilience can be hindered by existing limitations, yet traditional knowledge and intertribal organizations offer unique opportunities to adapt to the potential challenges of climate change.

While Tribes and Indigenous peoples across the Southern Great Plains generally experience the same climate change impacts as the rest of the Nation, these sovereign nations face unique challenges and opportunities in their response to climate change impacts. The biggest challenges to tribes and Indigenous peoples of the Southern Great Plains are those that threaten their ability to procure food, water, shelter, and preserve ancient cultural activities. Given the strong relationship between environment and culture, climate-induced changes to the seasons, landscapes, and ecosystems pose an existential threat to cultural traditions and community resilience. The impacts of excessive heat, drought, and the disappearance of native species are already disrupting some cultural practices. 

The region’s tribes and Indigenous peoples vary greatly in size. Some of the regions’ larger and wealthier tribal nations are working to develop and shape their own climate adaptation strategies. Conversely, some of the smaller nations, due to a relative lack of social and physical infrastructure, often struggle to exercise their sovereignty to respond to climate change. Consequently, the smaller tribes depend largely on the services, grant programs, and technology transfer capabilities of the Bureau of Indian Affairs and other Federal entities to support their climate adaptation efforts. 

Lack of physical infrastructure, tied directly to limited economic resources and power, poses a substantial obstacle to climate change adaptation for the tribes of the Southern Great Plains. While cities and other governmental jurisdictions make plans to build resilient physical infrastructure by using bonds, public–private partnerships, and taxes and tax instruments, only a handful of tribal nations have the ability to use these tools for climate adaptation. Most tribes and Indigenous peoples remain dependent on underfunded federal programs and grants for building and construction activities to improve the resilience of their infrastructure in the face of climate change threats. 

In response to their changing environment, some Tribes in the region are implementing adaptation measures and emissions reduction actions. Some of the larger and wealthier tribes have modeled construction and design of homes and large commercial building best practices on “green” or resilient net-zero carbon footprint designs. Increasing activity in community gardens, food recovery, recycling, water conservation, land-use planning, and investment in climate-resilient community design all signal opportunities for tribal nations to leapfrog significant obstacles other city, county, and state governments face when dealing with the costs of existing physical infrastructure that often make climate change adaptation difficult and incremental.

The preceding text is excerpted and abridged from Chapter 23 of the Fourth National Climate Assessment:Volume II: Impacts, Risks, and Adaptation in the United States. See Chapter 23: Southern Great Plains for references that support statements in this text.