outlook+water: May 2019

outlook+water: May 2019

SUMMARY:

  • Large parts of East and Central Texas received more than 10 inches of rain over the past month.
  • Recent rains have erased drought from the Texas landscape.
  • The odds of El Niño staying with us through the summer have increased to 70 percent.

After drought peeked in the window and knocked on the door for several months, in swooped weekly fronts across the state over the past four weeks, topping off reservoirs, flooding rivers, and eliminating drought conditions. Similar rains in New Mexico have swollen the Rio Grande and raised Elephant Butte Reservoir to over 20 percent full—good news for the El Paso area, but still a long way to go to fill the reservoir.

It has been a wet past four weeks! Large sections of the eastern part of the state received at least 10 inches of rain over the part 28 days with an even larger area receiving at least 6 inches. Most of the state has gotten at least 1 inch of rain.

Figure 1: Inches of precipitation that fell in Texas in the 30 days before May 15, 2019 (source).
Figure 1: Inches of precipitation that fell in Texas in the 30 days before May 15, 2019 (source).

 

The recent rains have erased drought from the Texas landscape with remnants of abnormally dry areas persisting, as of May 7, south of Houston, near Del Rio, and along a few parts of the Lower Rio Grande Valley (Figure 2a). A new abnormally dry area has appeared up in Dallam and Hartley counties (Figure 2b).

 

Figure 2a: Drought conditions in Texas according to the U.S. Drought Monitor (as of May 7, 2019; source).
Figure 2a: Drought conditions in Texas according to the U.S. Drought Monitor (as of May 7, 2019; source).

 

Figure 2b: Changes in the U.S. Drought Monitor for Texas between April 9, 2019, and May 7, 2019 (source).
Figure 2b: Changes in the U.S. Drought Monitor for Texas between April 9, 2019, and May 7, 2019 (source).

 

Almost all of the state has received greater than normal rainfall for the past four weeks (Figure 3). About half of the state has received twice as much as normal with a large area receiving three times the normal amount.

 

Figure 3: Rainfall as a percent of normal for the past 30 days (as of May 15, 2019; source).
Figure 3: Rainfall as a percent of normal for the past 30 days (as of May 15, 2019; source).

 

The North American Drought Monitor for the end of April had not yet been released by mid-May when we prepared this summary. April showed major improvements across Texas as well as in the headwaters of the Rio Grande (Figure 4a). Percent of normal precipitation in the Rio Grande watershed in Colorado, the primary source of water for Elephant Butte Reservoir, over the last 30 days shows the results of major rainfalls in the basin resulting in two to three times normal precipitation (Figure 4b).

 

Figure 4a: The North American Drought Monitor for April 30, 2019 (source).
Figure 4a: The North American Drought Monitor for April 30, 2019 (source).
Figure 4b: Percent of normal precipitation for the past 30 days for Colorado and New Mexico as of May 15, 2019 (source). The red line is the Rio Grande Basin. I use this map to see check precipitation trends in the headwaters of the Rio Grande in southern Colorado, the main source of water to Elephant Butte Reservoir downstream.
Figure 4b: Percent of normal precipitation for the past 30 days for Colorado and New Mexico as of May 15, 2019 (source). The red line is the Rio Grande Basin. I use this map to see check precipitation trends in the headwaters of the Rio Grande in southern Colorado, the main source of water to Elephant Butte Reservoir downstream.

 

Statewide reservoir storage increased slightly over the past month and remains about 5 percentage points above normal for this time of year (Figure 5a). Percent full status for individual reservoirs this month (Figure 5b) is about the same as last month although Elephant Butte Reservoir is above 20 percent full, up from 13 percent a month ago.

 

Figure 5a: Statewide reservoir storage since 2017 compared to statistics (median, min, and max) for statewide storage since 1990 (source).
Figure 5a: Statewide reservoir storage since 2017 compared to statistics (median, min, and max) for statewide storage since 1990 (source).

 

Figure 5b: Reservoir storage as May 15, 2019, in the major reservoirs of the state (source).
Figure 5b: Reservoir storage as May 15, 2019, in the major reservoirs of the state (source).

 

We are still under an El Niño Advisory with a 70 percent chance (up from 65 percent a month ago) of weak El Niño conditions continuing through the summer and a 55 to 60 percent chance through the 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 temperature anomalies for the Niño 3.4 Region as of April 19, 2019 (modified from source).
Figure 6. Forecasts of sea surface temperature anomalies for the Niño 3.4 Region as of April 19, 2019 (modified from source).

 

 

Author

 

IMG_5251Robert Mace,
Interim 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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