outlook+water: October 2018

outlook+water: October 2018

SUMMARY:

  • September was the wettest September on record for Texas and the third wettest month on record.
  • Drought is down to affecting 12 percent of the state.
  • Statewide reservoir levels continue to rise.
  • The odds of El Niño paying a visit are up to 70 to 75 percent.

Our cats have not been happy. Over the past couple of months, their hollow gazes have been fringed with disappointment and concern, plaintive mews escaping their cute little lips: “You write about the weather, but you don’t seem to do anything about it. Where’s the sun?!?!” Indeed, the weather pattern has changed dramatically from sunny, dry days to overcast and rainy (and precious few moments for sunbathing).

The big rains in north-east, north-central, and central Texas have continued from last month with sizable parts of the state receiving 10 inches or more and some parts seeing more than 20 inches (Figure 1a). According to the National Centers for Environmental Information, September 2018 was the wettest September on record (since 1895) and, at statewide precipitation total of 6.77 inches, the third wettest on record after May 2015 and August 2017 (source).

As I write this, massive rains in the upper Hill Country have washed out a bridge on the Llano and, almost overnight, filled up Lake Travis and Lake Buchanan (Figures 1b and 1c). Even Choke Canyon Reservoir on the Frio saw a bump in storage over the last month that pulled it out of record low territory (Figure 1d).

The statewide drought is slightly improved now (46 percent of the state in drought; Figure 2) than a month ago (47 percent); however, recent weather patterns rearranged drought across the state removing drought along the Gulf Coast, lessening severity in many parts of West Texas, and doubling down on the north-to-south center of the state (Figure 3).

Figure one
Figure 1a: Inches of rain that fell in Texas in the 30 days before October 16, 2018 (source).
figure 1b
Figure 1b: Reservoir storage in Lake Travis since 2016 compared to statistics (median, min, and max) for conditions since 1990 (source).
figure 1c
Figure 1c: Reservoir storage in Lake Buchanan since 2016 compared to statistics (median, min, and max) for conditions since 1990 (source).
Figure 1d: Reservoir storage in Choke Canyon Reservoir since 2016 compared to statistics (median, min, and max) for conditions since 1990 (source).
Figure 1d: Reservoir storage in Choke Canyon Reservoir since 2016 compared to statistics (median, min, and max) for conditions since 1990 (source).

The amount of Texas in drought over the past month has again more than halved from 29 percent to 12 percent; however, small parts of West Texas are still suffering from extreme and exceptional drought conditions and extreme drought has developed in Far West Texas, along the Culberson-Hudspeth county line (Figure 2a). We saw improvements in drought conditions across most of the state (Figure 2b). Rainfalls over the past week should result in further drought improvements in the eastern half of the state.

 

Figure 2a
Figure 2a: Drought conditions in Texas according to the U.S. Drought Monitor (as of September 18, 2018 (source).
Figure 2b: Changes in the U.S. Drought Monitor for Texas between September 11, 2018, and October 9, 2018 (source).
Figure 2b: Changes in the U.S. Drought Monitor for Texas between September 11, 2018 and October 9, 2018 (source).

Ninety-day rainfall deficits continue to improve with sizable parts of the state with at least twice as much rainfall as normal (Figure 3). Even with all the recent rains, there are still widely distributed splotchy parts of East Texas, the Rio Grande Valley, the High Plains, and Far West Texas where rainfall is below normal.

Figure 3: Rainfall as a percent of normal for the past 90 days (as of October 16, 2018; source).
Figure 3: Rainfall as a percent of normal for the past 90 days (as of October 16, 2018) (source).

 

As I write this, the North American Drought Monitor for conditions at the end of September had not been published, so I’m showing conditions at the end of August again (Figure 4a). Rainfall deficits over the past 90 days for the United States shows continuing drought in the headwaters of the Rio Grande in southern Colorado (Figure 4b).

Figure 4a: The North American Drought Monitor for August 31, 2018 (source).
Figure 4a: The North American Drought Monitor for August 31, 2018 (source).
Figure 4b: Percent of normal rainfall for the past 90 days for the continental United States as of October 17, 2018 (source).
Figure 4b: Percent of normal rainfall for the past 90 days for the continental United States as of October 17, 2018 (source).

Persistent rains have continued the upswing in statewide reservoir storage, lifting storage from 78.1 percent on September 23rd to 84.3 percent on October 17th (Figure 5a). Reservoirs in the eastern part of the state are generally showing increases in storage (compare Figure 5b, this month, to Figure 6b, last month).

Figure 5a: Statewide reservoir storage since 2016 compared to statistics (median, min, and max) for state-wide storage since 1990 (source).
Figure 5a: Statewide reservoir storage since 2016 compared to statistics (median, min, and max) for statewide storage since 1990 (source).
Figure 5b: Reservoir storage as October 17, 2018, in major reservoirs of the state. (source; I’m not showing Elephant Butte this month because the source had a glitch that showed the reservoir as 100 percent full!)
Figure 5b: Reservoir storage as October 17, 2018, in major reservoirs of the state. (source; I’m not showing Elephant Butte this month because the source had a glitch that showed the reservoir as 100 percent full!)

We remain under an El Niño Watch for the fall and winter with increased certainty of 70 to 75 percent. The consensus projection shows El Niño conditions arriving this fall (Figure 6). El Niños generally result in wetter-than-normal and cooler-than-normal conditions for Texas and act as a tropical storm suppressor.

Figure 6. Forecasts of sea surface temperatures anomalies for the Niño 3.4 Region as of October 11, 2018 (modified from source).
Figure 6. Forecasts of sea surface temperatures anomalies for the Niño 3.4 Region as of October 11, 2018 (modified from source).

The U.S. Seasonal Drought Outlook through December is the same as last month’s with drought improvements projected for across the state (Figure 7).

Figure 7: The U.S. Seasonal Drought Outlook for August 16 through December 31, 2018 (source).
Figure 7: The U.S. Seasonal Drought Outlook for September 20 through December 31, 2018 (source).

Author

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Dr. Robert Mace,
Deputy Executive Director & Chief Water Policy Officer at The Meadows Center for Water and the Environment
Robert Mace is a Professor of Practice in the Department of Geography at Texas State University. Robert has over 30 years of experience in hydrology, hydrogeology, stakeholder processes, and water policy, mostly in Texas. 

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