Monday’s storm hit urban areas of North Texas with a vengeance, flooding roads, sidewalks and homes across the Metroplex.
But the record rainfall didn’t translate into much higher water levels for the reservoirs that supply drinking water to Tarrant County cities, according to initial data collected by the Tarrant Regional Water District.
“It definitely helps, and we’re very grateful for every drop of the water that was captured for water supply, but it really doesn’t change the picture for drought conditions,” said Zach Huff, the agency’s water resources engineering director.
While Lake Arlington rose 6.78 feet between Aug. 22 and Aug. 23, Cedar Creek Reservoir and Richland-Chambers Reservoir – both located southeast of Dallas – rose .86 feet and .21 feet respectively. The two reservoirs provide about 80% of the drinking water that Tarrant County residents and businesses use on a daily basis.
The downpour was concentrated just north of the Benbrook Lake watershed and just south of the Eagle Mountain Lake watershed, Huff said. That means the rainfall mostly missed the reservoirs in desperate need of water during the worst drought in Texas since 2011.
“What’s very unique about this storm is that in downtown Fort Worth, it was very, very intense,” Huff said. “You see the river flowing like that, and you’re thinking: ‘This has to instantly fill the reservoir.’ And then you look at the reservoirs, and they’re coming up about a foot. It’s just all about where the rain hits.”
Overall, the water district’s system went from about 80% full to just over 82% full over that 24-hour period, Huff said. He suspects that number will increase to 83% as the Cedar Creek Reservoir absorbs more water runoff from the storm.
Earlier this month, water district officials said they would likely instruct their customers – including Fort Worth, Arlington, Mansfield and other municipalities across 11 counties – to enter Stage 1 of its drought contingency plan by late September or early October. Stage 1, or the Water Watch stage, is triggered when total water supply falls beneath 75% full.
Under Stage 1, cities must reduce total water use by 5% through enforcing requirements to water lawns no more than twice per week and prohibiting outdoor watering between 10 a.m. and 6 p.m. Fort Worth already implements those requirements year-round, but Arlington and Mansfield do not currently have the rules in place.
Stages of drought contingency plan
Stage 1, Water Watch: Raw water supply falls beneath 75% full. Goal is to reduce total water use by 5%. Cities would limit outdoor watering to twice per week and prohibit watering between 10 a.m. and 6 p.m.
Stage 2, Water Warning: Raw water supply falls beneath 60% full. Goal is to reduce total water use by 10%. Cities would prohibit outdoor watering more than once per week and ask residents to postpone new landscaping. Agencies would send more public messaging to conserve.
Stage 3, Water Emergency: Raw water supply falls beneath 45% full. Goal is to reduce total water use by 20%. Cities would prohibit all outdoor watering with hose-end sprinklers and automatic irrigation systems, including at parks, golf courses, and sports fields. Businesses and residents would be banned from washing paved areas or buildings without permission.
While the water district is still adjusting its models to account for the massive storm, Huff believes the deluge will delay Stage 1 water restrictions by a few weeks.
There is reason for optimism following the second-highest 24-hour rainfall total in North Texas history, Huff said. Demand for water is expected to drop significantly because residents will have less need to water their lawns.
Before the storm, the district’s water use was up to about 550 million gallons per day. That number dropped to 285 million gallons overnight.
“Pushing demand down and decreasing evaporation will help with the drought very significantly.” Huff said. “We lose more to evaporation than we actually use and consume. Even though it’s not raining that much today or tomorrow, just having a few days of cloud cover really cuts down on evaporation.”
Water demand typically drops in September to an average of about 400 million gallons per day, and then down to 300 million toward the beginning of October depending on weather conditions, Huff said. All of those factors bode well for ensuring water supply remains stable, he said.
“When we look at our demand curves and how we model and project them, we’re right at the point where we start seeing demands decreasing,” Huff added. “It’ll be interesting when (water demand) rebounds as things warm back up, and as it rebounds, they shouldn’t be rebounding back to where they were. They should be rebounding back a little bit lower.”
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