A stark divide in Texas shows what climate change looks like
The state of Texas is giving us a glimpse into what researchers mean when they warn that climate change will widen the difference between the haves and the have-nots. A steady parade of storms this spring has formed along a stark line of delineation, leaving central and east Texas with saturated ground and full reservoirs, while parts of west Texas suffer from drought, depleted reservoirs, and parched, blowing dirt.
The juxtaposition between too much and too little rain gets more complex as we march into summer and the possibility of tropical systems; we don't get to choose where that water goes. While some regions along the Rio Grande desperately need the rain, other south Texas locations are still contending with a surplus.
Further complicating the story of water in Texas is Mexico - the drought does not cease to exist at the border, and the country is facing its worst drought in over a decade. Along the border, the drought is causing tensions between the U.S. and Mexico over water resources for farming.
A battleground state
Springtime in Texas can be synonymous with hailstones and tornadoes. The giant state becomes a battleground between huge influxes of moisture from the Gulf of Mexico to the south and dry desert air from the west. This collision of forces can create its own front to provide lift and energy in the atmosphere for thunderstorms to develop.
We call this a dry line, and it almost always stretches across both panhandles of Oklahoma and Texas when it forms. Along this line, storms develop and progress to the east. Behind them, to the west, is left dry.
This year, the Gulf of Mexico is running a fever with way above-average temperatures, fueling increased moisture for storms to develop. The Dallas-Ft. Worth metroplex broke a number of daily rainfall records, and it has had among the top five wettest starts to the year.
In locations like Waco and Goldthwaite, it was the rainiest May on record. Wheat farmers have had to adjust their harvest schedule due to soggy fields. Parts of the Trinity River have come down from their major flood stage to moderate after a period of drier weather, but the fallout from the extreme spring rains continues.
On the other side of the coin, the west side of the state, especially in the deep southern reaches along the Mexican border, are experiencing drought. Recent rains have improved conditions through the panhandle and parts of West Texas, but most reservoirs remain remarkably low, some at only 1-2% of their capacity.
Along the Rio Grande, from Big Bend National Park toward Laredo, some locations have only seen 10% of the average rainfall to this point in the year. Impacts to agriculture have been felt from this region north into the Edwards Plateau as the soil has become parched, resulting in blowing dirt and delayed planting.
In fact, earlier this year, the last remaining sugar grower in Texas had to shut down its operation due to a lack of water resources. Sugar cane requires three times as much water as soybeans and corn, also cultivated in south Texas, and years of unreliable rainfall have made production impossible.
American and Mexican farmers compete for water
This is where Mexico enters the picture. The sugar cane producer was located along the Rio Grande and used water allocated from it to irrigate its crop. This river that forms the border between the U.S. and Mexico is a shared water commodity. As a part of a water treaty of 1944, the U.S. provides water from the Colorado River to Mexico, while Mexico is expected to share an average of 350,000 acre-feet of water from the Rio Grande each year.
The Falcon Reservoir is one of the two reservoirs that the water from the Rio Grande is diverted to by Mexico. It currently sits at only 10% capacity. Only about a quarter of the water required by the treaty has been delivered to the U.S. from Mexico over the last four years.
There are a number of factors as to why water levels are so low, upstream water use and politics among them, but the biggest player by far has been the drought. One hundred percent of the northernmost Mexican state of Chihuahua is experiencing drought, with 40% in the most dire category of exceptional.
Relief coming from the tropics?
Could there be hope from the tropics? Just this week there is an expected deluge of water from tropical activity in the Gulf of Mexico that could be welcome in this parched region of south Texas and northern Mexico - that is, if it doesn't fall too fast. Even though the soil is extremely dry, the risk of flash flooding remains.
And not all of Texas wants this rain.
With the current tropical system prompting a moderate chance of excessive rainfall in some of the same areas that have flooded this spring and in 2017, anxiety is high.
Those who lived through Hurricane Harvey just seven years ago are understandably on edge when hurricane season approaches. Harvey was the "most significant tropical cyclone rainfall event in U.S. history" with over 60 inches of rain falling in southeast parts of the state, flooding hundreds of thousands of homes and killing 68 people.
Although historic rain is not expected with this system, climate change has made extreme rainfall events increasingly common. Following Harvey, researchers estimated that between 20-37.7% more rain fell than would have in a world without climate change. This is as much as 15 inches more rain in some locations.
As a result of rising temperatures, extreme rainfall has increased across the U.S., including in places like Texas. When the temperature is higher, the atmosphere can hold more moisture, creating a higher potential for extreme rainfall events.
But in places without a source of moisture - such as the Gulf of Mexico - higher air temperatures also mean an increased likelihood of drought, because the warmer the air, the higher the evaporation rate of water from soil and plants. In Texas, climate change has increased the temperature by an average of 3 degrees Fahrenheit since the preindustrial era.
Bottom line: Climate change means increasing extremes in drought and rainfall. And right now, Texas is showing the consequences of both.