Downloadable Media

• Download Video
• Download Clean Video (no graphics)
• Download Audio-only
• Download Video Caption

Transcript

Dr. Mark Wentzel – Hydrologist, Texas Water Development Board

Hi everyone, and welcome to the Texas Water Development Board's latest Water and Weather report. I'm Dr. Mark Wentzel, a hydrologist in the Surface Water Division here at the agency. And today, we'll be taking a look at conditions for our state at the end of June, as well as a closer look at one of the datasets we use for this report. 

Let's take a look at some of the big water and weather headlines. Overall, June rainfall was near normal while temperature was above normal across the state. At the end of June, 25 percent of the state was in drought, down one percentage point from the end of May. Statewide, storage in our water supply reservoirs is about 78 percent of capacity, about seven percentage points below normal for the end of June.

In the next few months, drought is expected to expand in the Panhandle and West, Central, and North Texas. Let's take a closer look at the U.S. Drought Monitor map for Texas. The area of the state impacted by drought didn't change much in June. Improvements in South Texas were almost completely offset by degradations in Central and West Texas. At the end of the month, 25 percent of the state is impacted by drought, down only one percentage point from May.

Why do we use the U.S. Drought Monitor map to monitor drought in Texas? Well, there are many ways to measure drought. Folks interested in meteorological drought tend to focus on comparing precipitation, measured in recent weeks or months, to long-term averages for those time periods. Folks interested in agricultural drought tend to focus on measuring soil moisture, which, in addition to precipitation, is impacted by soil properties, temperature, seasonal plant activity, and other factors. Folks interested in water supply focus on stream flows, reservoir volumes, and aquifer levels that are impacted by many more conditions and react to drought on timescales of months to years to decades.

Drought indices like the Palmer Drought Severity Index and drought categories used by the U.S. Drought Monitor are examples of attempts to build a composite interpretation of the many ways to measure drought. Mapping drought is easy when unusually dry or wet conditions have been in place in the area for months or even years. Under these conditions, all the various ways to measure drought align. Where things can get messy is during the transition from long-term drought to normal or the transition from long-term normal to drought. For example, in the winter after a wet fall, rainfall can be historically low for a month with limited declines in soil moisture or reservoir volumes. Or in the fall after a summer of drought conditions, one month of normal rainfall can provide limited improvement to soil moisture and no improvement to water supplies. In these cases, the many ways to measure drought are not likely to align.

So, what's the best way to depict drought across Texas? I rely on the U.S. Drought Monitor maps. As a surface water hydrologist, my interest in drought revolves around stream flows and reservoir volumes. I just don't have the required background to consider all the other factors that go into providing a general assessment of drought. In fact, no one person could pull it off. In our state, the U.S. Drought Monitor maps are developed by the Office of the State Climatologist at Texas A&M University, assisted by local offices of the National Weather Service and the Texas A&M AgriLife Extension Service. They consider a whole suite of factors, including rainfall, soil moisture, and hydrologic data, range and crop conditions, Palmer Drought Severity Index, and other indices when constructing their weekly drought maps. Their methods are data-driven, but they do rely on professional judgment when datasets may be pointing in different directions, and they're always trying to improve.

If you've got specific critiques of the drought designations in your county, reach out to your local extension service or National Weather Service office. I'm sure they'd be happy to hear from you. There are many ways to map drought, and we don't have time to look at all of them in these reports. So, if you're interested in seeing other ways to map drought, use the link below to reach the drought dashboard produced by the Texas Water Development Board and the office of the State Climatologist. And until next time, I hope you all stay healthy and safe.