Will January’s rainfall impact Texas drought conditions? Officials say it’s complicated
Texas has been in a drought since September 2021, with Brazos River Authority reservoirs remaining below full capacity despite recent rainfall.
The Brazos River Authority has three water supply reservoirs in the Brazos River Basin: Possum Kingdom Lake, Lake Granbury and Lake Limestone.
Aaron Abel, Water Services Manager with Brazos River Authority, said the Possum Kingdom reservoir, about two and a half hours away from Fort Worth, is at 82% full and 6 feet below full elevation. Lake Granbury, a smaller reservoir about an hour from Fort Worth, is 86% full.
“The drought that started in September of 2021, it’s kind of impacted the Brazos more so than it has, say, the Trinity River and all the other basins further to the east,” Abel said. “This particular drought, it’s kind of impacted further west you go and then also further south you go. So some of our downstream reservoirs are even more significantly impacted than Possum Kingdom and Granbury.”
Although Texas has seen rainfall toward the end of January — with more expected in the Fort Worth-Dallas area going into February — the state’s drought conditions are not going away anytime soon.
How does rainfall factor into water supply?
Rainfall directly impacts reservoir water supply, but the amount of rain that comes down is not necessarily the amount that will end up in the reservoirs.
Abel said the Brazos River Authority watches every rain event to see if it will initiate runoff to fill the reservoirs. As of January, he said there needs to be more rain in order to get rivers and creeks flowing into the reservoirs and replenishing supply.
Typically, rainfall doesn’t happen often in the winter, so there currently isn’t much change in water supply conditions.
How much rain does it take to ensure the reservoirs are full?
It’s difficult to quantify exactly how much rain it would take to fill up the reservoirs.
Abel said it would likely take multiple rounds of 3-5 inches of rain over a widespread area upstream of the reservoirs for multiple weeks in order to fill up the reservoirs.
When it rains, the amount of water that falls into your rain gauge is not the same amount that runs off into lake reservoirs.
Here’s what the Brazos River Authority factors in when determining lake levels after rainfall:
Where the rain falls
How heavy the storm is
If the rain sinks into the ground or runs off
The amount of water already in the lake
Will the recent rains be enough to get Texas out of a drought?
Recent rains have not had major impacts on drought conditions, but spring showers could help.
Currently the United States is under La Nina conditions, which typically causes warmer and dry conditions in the south. With La Nina expected to end in March, Abel said normal spring rains would help with the drought conditions.
During the winter, plants and other vegetation are dormant and absorb less water than normal so rain is able to saturate soil and initiate runoff.
“If we continue to get some rain, especially here in the late winter, we may be able to see some runoff develop associated with rain events,” Abel said.