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How Current Drought Compares to 2011

The Texas Water Development Board (TWDB) recently produced a fascinating short video that puts the current drought in historical perspective by comparing rainfall, temperature, and water supplies to 2011. The text and visuals below are adapted from Dr. Mark Wentzel’s presentation. Wentzel serves as a hydrologist for the TWDB.

Wentzel’s charts depict statewide averages. The Houston region has had significantly more rainfall. So look at Wentzel’s data for trends happening around us. I’ll show Houston data at the end of this post.

Comparison to 2011 Drought

Wentzel says that June was warmer and drier than normal for much of the state, the fourth consecutive month with those conditions. At the end of June, drought conditions covered 86 percent of the state, up eight percentage points from the end of May. Storage in our water supply reservoirs is at 75 percent of capacity, ten percentage points below normal for this time of year. So, Texas is in a significant drought, the worst since 2011, but not worse than 2011.

Highlights of Wentzel video

Statewide Precipitation Averages

The State average rainfall from January to June of this year: 7.8 inches, about 60 percent of normal. Bad as that may be, it’s better than in 2011 when we received less than six inches in the first half of the year, only about 40 percent of normal.

Statewide Texas precipitation averages

Comparison to 2011 Temperatures

On the next chart, Wentzel shows monthly average temperatures across the entire state for both 2022 in orange and 2011 in red. Black dots show the 20th century average for comparison. He shows maximum and minimum temperature records in gray. The gold line represents January to June of this year.

Statewide Texas temperature averages

Temperatures have been above average five out of six months. That additional heat has certainly contributed to drought, but monthly temperatures in the first half of 2011 were even hotter for four of those six months.

In 2011, the real heat came in June, July, and August when we set maximum temperature records each month.

Dr. Mark Wentzel, TWDB

Temperatures the rest of the summer and 2022 are expected to be warmer than average, but not to exceed 2011 temperatures.

Percent of State in Drought

Low rainfall and high temperatures during the first half of 2022 have brought significant drought to Texas. The U.S. Drought Monitor map for conditions as of June 28 shows 86 percent of the state impacted by drought, up eight percentage points from the end of May. More of the state is experiencing drought at the end of June this year than for any June since 2011, when 96 percent of the state was in drought.

Effect on Water Supply

Statewide, our water supply reservoirs are being impacted by the current drought, but not as significantly as in 2011. The dark line on this chart shows how storage this year compares to minimum, maximum, and median values for the day of the year from data going back to 1990. Lighter lines show how we did in 2021 and 2020. The red line shows how we did in 2011.

Texas statewide totals expressed as percent of full capacity

We began 2022 with water supply storage more than two percentage points lower than normal for the time of year. By the end of June, we’ve fallen to about ten percentage points lower than normal.

In 2011, water supply began the year closer to normal, but fell farther and faster than in 2022. By the end of June, storage was about one and a half percentage points less than this year. In the second half of 2022, Wentzel expects additional storage declines, but not as severe as in 2011 when the State reached 30-year lows by mid-October.

Bottom Line for State

We are in a significant drought, even if it’s not as bad as 2011. But the real test won’t come this summer or even this year. Our water supply systems are designed to withstand a multi-year event. Will 2022 lead to a multi-year event? It’s too early to tell, says Wentzel. “But it’s never too early to conserve water and manage demand.”

Houston

The charts below comes from the National Weather Service Climate site and depicts conditions at Bush Intercontinental Airport.

The top half of the first shows temperatures. It depicts highs in red, average ranges in green, and lows in light blue for ever day of the year. The dark blue lines show actual temperature observations year to date.

The bottom half shows actual precipitation compared to the average. You can see that for part of the year, we were actually above normal. But starting around June 1, we fell behind.

The last chart shows temperatures in July to date. The dark blue lines show actual temps compared to highs, the normal range, and lows for every date. The three stars indicate records or ties.

Posted by Bob Rehak on 7/15/22 based on information from TWDB, NWS and Dr. Mark Wentzel

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