Thursday, May 19, 2016

Central Texas is "Flash Flood Alley"

No Drought
Lovelady well height: 533.89 ft-msl (119.53 ft-Depth to Water)
Barton Springs: approximately 111 cfs 10-day average


Central Texans are no strangers to floods, especially flash floods. In fact, according to the LCRA, the Hill Country and Central Texas region has even earned the nickname Flash Flood Alley due to a “greater risk of flash flooding than most regions of the United States.” In fact, according to the USGS, Texas has more than double the flood fatalities (since 1960) of any other state.

So what is the cause behind Flash Flood Alley? Floodsafety.com provdes a video graphic overview of the key factors that result in higher flash flood occurence across Central Texas. One key point is the region’s unique geographical location, often positioned at the meeting point of air masses converging from the Gulf and the Pacific. The resulting storms tend to generate high rainfall over short periods of time. When lots of rain falls in too short a time to allow for infiltration, flash floods are sure to follow.  

There are several dams in place, controlled by the LCRA, across the six Highland Lakes to help manage floodwaters from heavy rain in the region and prevent greater disasters in areas downstream. These are detailed in the graphic at left (LCRA), showing their progression toward the Gulf of Mexico. Hydrologists at the LCRA River Operations Control Center (ROCC) monitor these sites at all hours and manipulate the dam floodgates.

A year ago in May 2015, Wimberley and Houston experienced deadly floods. Last month, Houston had another. Brian K Sullivan of Bloomberg News explains that “Events like these are often called ‘100-year floods,’ but that can be misleading. The U.S. governments began using the term in the 1960s to describe a flood that has a 1 percent chance of happening in any given year, not a chance of happening only once a century.”

We should note that predictions of historic floods don’t necessarily account for other conditions that can alter the potential for an occurrence, for example climate change or an unusually strong El Niño or La Niña. “That’s why the 100-year event is such a moving target, especially in an urban environment,” said Chuck Watson, director of research and development at Enki Research, which develops tools to measure hazards. “Someone builds a couple of parking lots, and you just turned a 100-year event into a 70-year event because of the impervious surfaces… Asphalt doesn’t soak up rainwater; it just sends it somewhere else, such as into the house next door. When you add in natural climate cycles, the results are further skewed...One of the influences of El Niño is to send more rain across the southern U.S. In a situation like that, the chances of a catastrophic flood might rise to one in 20 according to Chuck Watson.” For more information on 100-year floods and how they’re defined, check out this article from the USGS.

With flooding common in periods of heavy rain, folks in Central Texas should live by these  simple, but critical, rules to stay safer:

  1. Don’t drive over flooded roads or low water crossings; “turn around, don’t drown.”  If you need to drive during rainy or flooded conditions, use ATXfloods.com for current updates to help you plan a route around dangerous areas
  2. If you find yourself stuck in a structure, or on high ground, during extreme flood conditions, do not try to swim for it. Stay where you are as long as possible to allow rescuers the opportunity to come to you

Take a look at this video, shared on Facebook by Robert Teague, of flash flooding in action. As you can see, a massive pulse of water is followed by a buildup of debris proceeding like a tiny monsoon over a low-water crossing. Needless to say, this type of flow is extremely dangerous.

Thursday, May 5, 2016

Aquifer Status


No Drought
Lovelady well height: 532.22 ft-msl (121.20 ft-Depth to Water)
Barton Springs: approximately 110 cfs 10-day average


The graph shows the groundwater level elevation at the Lovelady monitor well from 1991 to the present. The Lovelady well is one of the District’s drought index wells (in addition to flow at Barton Springs). The graph illustrates that over the past two decades there have been dramatic peaks and critical lows. Due to the recent wetter-than normal rainfall in the region, the groundwater-level elevation in the Lovelady well has reached 531.8 ft-msl. This elevation is well above the average of 491.7 ft-msl. The current levels are similar to peak measurements taken at Lovelady 11 years ago in May of 2005 (531.5 ft-msl), and higher than levels reached in 2007 (the 3rd wettest year on record for the region). Barton Springs is also flowing at very high rates of greater than100 cubic feet per second (cfs), also above it’s average levels of ~53 cfs.



Climatologists attribute the wet conditions to a surprisingly strong El Niño phenomenon in 2015-16, which has already delivered 11 inches of rainfall this year—in addition to the high rainfall in 2015. Only time will tell if the stronger phenomenon this year will continue the trend of increasing Lovelady measurements beyond 2005 levels.


All this is good news for the aquifer as we enter into our normal hot and dry summer period. Conditions are high enough that we won’t likely approach significant drought conditions in 2016. However, after the creeks stop flowing, we know water levels will begin their usual decline.

Wednesday, April 6, 2016

April 2016 Edwards & Trinity Aquifers Update

No Drought
Lovelady well height: 529.55 ft-msl (123.87 ft-Depth to Water)
Barton Springs: approximately 103 cfs 10-day average

The effects of increased rainfall through much of the past year (52 in since last April) have been evidenced by increased water levels in the Edwards and Trinity Aquifers. The graphic below depicts the rise in water level in the BSEACD Lovelady monitor well since May of 2015. The steady rise in water levels since November 2015 almost came to an end at the beginning of March 2016 when 3 inches of rain over a four-day period brought more recharge to the Edwards Aquifer. This additional rainfall caused flow in the creeks that pass over the recharge zone to increase, thereby increasing recharge to the aquifer. And, water levels in Lovelady are rising again, but slowly.
Notably, water levels at the Lovelady well are currently at their highest mark since 2007 when a depth to water of 126.1 ft was recorded. 

As an indicator of recharge to the Trinity Aquifer, Jacob’s Well Spring has benefitted from the wet 2015 and has maintained flow greater than 10 cubic feet per second (cfs) through the beginning of 2016 but flow, similar to other streams and springs, is now beginning to recede.

In the long term, the presently-strong El Niño has begun visibly weakening, according to NOAA. This weakening could lead to decreased rainfall, decreased stream flow, and decreased groundwater levels. That said, the April rainfall total is already a quarter of an inch (0.27 in) five days into the month and meteorologists predict more rain to come.

Friday, March 25, 2016

El Nino Continues, Aquifers Benefit

 
No Drought
Lovelady well height: 529.06 ft-msl
Barton Springs: approximately 104 cfs 10-day average

As predicted, the current El Niño phenomenon has ranked among the strongest (and for some the most disruptive) in history. As seen in this graphic from the National Weather Service, the characteristic warming of the ocean has only slowly begun to diminish into March. This occurrence ties the previous 1997-1998 instance as the strongest on record. Climate predictions indicate above-normal precipitation continuing into May 2016. It’s also predicted this will hasten a strong hurricane season later this year. Looking ahead, climatologists predict there will likely be a shift into a La Niña period this fall. For more information, visit this article on Weather.com.

Locally, we’re still benefiting from increased rainfall due to El Niño. According to the LCRA, Austin and surrounding areas have received 1 to 2 inches of rain in the last two weeks adding to the 2016 total of between 6-8 inches.  As of March 22, 2016, the drought monitor lists all of Central
Texas as drought free.
IMG_0993.JPG
Above average rainfall continues to yield recharge to the Edwards Aquifer, especially at sites like Antioch Cave on Onion Creek. Below, take a look at a video of recharge in action at Antioch cave, forming a whirlpool at the vault built over it.
https://youtu.be/xxb-1Ms70Pw

Tuesday, January 12, 2016

Edwards and Trinity Aquifer conditions, A Year In Review


No Drought
Lovelady well height: 524.60 ft-msl
Barton Springs: approximately 104 cfs 10-day average

          2015 began with some much-needed relief from Stage II Alarm Drought conditions. After rejuvenating rainfall in the preceding months, the Board declared No-Drought on January 29. Fueled by a stronger-than-usual El Niño phenomenon, heavy rainfall continued throughout the spring. A brief dry spell in summer was quickly overtaken by even heavier rains in the fall.  In a nutshell, 2015 was a wet, then briefly dry, then even wetter year.

          Steady recharge increased water levels in the Edwards and Trinity aquifers as well as Barton Springs and Jacob’s Well flow early in 2015. Aquifer levels continued an upward trend and received an even larger boost from extremely heavy rainfall on Memorial Day, as 5.20 inches fell on Camp Mabry. Total May rainfall in Austin reached a record-breaking 17.59 inches, topping the previous tally of 14.10 inches in 1895. The Hill Country and San Marcos received between 12 -15 inches. Rain temporarily disappeared from the region in July and August to round out the summer.

          Central Texas became perhaps more familiar than ever with the El Niño phenomenon, as 2015 boasts one of the strongest in history. As a result, the dry spell of summer was short-lived. An historic Halloween flood unleashed an astounding 18.5 inches in Buda, with surrounding areas reporting between 11 and 16. This event topped the previous Halloween 2013 and Memorial Day 2015 floods in stage level and discharge on Onion Creek. Antioch cave began taking desired recharge after storm runoff flows passed.

          In the 2015 Hydrograph (above, click to enlarge) includes three graphs depicting periods of above and below average rainfall at Camp Mabry during 2015 and the resulting effects on the Lovelady monitor well  and Jacob’s Well spring. At periods of above average rainfall, visible in the lowest graph, the discharge level at Jacob’s well spikes dramatically. Throughout the year, and at accelerated rates after rain events, the Lovelady Monitor well depth to water slowly increased.

          After continued rains through the 2015 Holiday Season, Texas remains drought-free as of January 5. The Lovelady well and Barton Springs drought trigger sites remain well above their respective average thresholds. The outlook for 2016 according to the National Oceanic and Atmospheric Administration is a still strengthening El Niño that could last into early spring. This perhaps being the strongest El Niño since 1997-1998.

On behalf of the BSEACD, Happy New Year!

Monday, November 30, 2015

What Makes a Good Monitoring Well?

Aquifer conditions are dynamic and therefore water levels can fluctuate because of drought, recharge, and pumping.  Monitor wells help track these changes and inform policy to help protect water supplies and spring flow for all users.  After all, groundwater is a shared resource.
We often get asked the question, what makes a good monitor well? In short, the answer is that a well that is representative of the aquifer we are interested in. But, while water levels can be measured in most wells, the nature of the geology and well construction usually limits the potential for a well to be used for monitoring purposes.
Diagram of a typical well headAt the surface, groundwater wells can appear  similar, however  individual wells--even neighboring ones--can be constructed in very different ways.  For example, different depths of wells, or different depths of the casing influences production rates and water quality.  Well records (e.g. driller's logs, geophysical logs, video logs) are key to understanding a well's construction.
Drillers use a variety of construction methods to balance sufficient quantity (yield) with good (a relative term) water quality.  The Edwards and Trinity Aquifers are each made up of many layers of rock.  Water quantity and quality can vary from layer to layer.  The location and depth of a well, and how it is constructed, determine what rock units that well can access and therefore influence its yield and quality. The construction of a well such as its casing depth, amount of cement, and/or packers can seal off undesirable layers. At the same time, the well is left open or screened at selected intervals to allow water to enter the well at the desired layers.
Every well should have a driller's log that documents well depth, well construction, pump setting, and an initial water level.  In 2003, all well drillers were required to submit this information online, so data on wells drilled in the last 12 years is much more accessible. In sensitive areas, a more detailed geophysical log is often required to inform the well construction and to limit the mixing of undesirable waters between aquifers (and into the well).
On the top of the well (called well head), most contain a 1/2" or 3/4" hole that can allows the measurement of the water level in the well (also called an observation port). To prevent debris or contaminants from entering the well, this port is usually plugged by a blue plastic square-head nut. The water level can be measured through that port using either an eline (electric measuring tape; reliable but time-consuming) or a sonic meter (bounces a sound wave off water surface; fast but requires verification).
District staff maintain over 30 continuous water level monitoring sites in the Edwards and Trinity aquifers. A pressure transducer and the cable installed in a domestic well with a drop tube.Many of the wells are domestic wells that are in use.  These sites are equipped with a probe (a pressure transducer) that is programmed to measure the water level hourly.  Staff stop by to download the data about once a quarter, or more frequently for a specific study. These monitoring wells are plumbed with a drop pipe that keeps the pressure transducer and cable away from the pipe that brings water to the surface and the pump wires. Monitoring does not interfere with operation of the well.
Everyone benefits from an efficient monitoring network.  Optimal monitor wells are representative of the aquifer and area we are interested in learning about. Monitor wells need good construction information (logs) and must be readily accessible. Many thanks to all of the well owners who allow this essential access to water level data, respond to conservation requests, and responsibly use and maintain their wells.  We are all in this together.
Useful links:
Geologic diagram of aquifer layers (stratigraphic column)

Thursday, November 5, 2015

Pouring It On

             For many in Central Texas, the morning before Halloween was much more frightening than the holiday itself. An historic flood, larger than the previous Halloween 2013 and Memorial Day 2015 events, occurred as a large front of heavy rain and thunderstorms swept across the region early Friday.
USGS Stream Gage on Onion Creek at Twin Creeks Road:

Halloween 2013: Gage Height: 20ft; Discharge: 12,000 cfs
Memorial Day 2015: Gage Height: 22ft; Discharge: 17,000 cfs
Halloween 2015: Gage Height: 28ft; Discharge: 45,000 cfs

In Buda, the final rain total reached an astounding 18.46 inches. Surrounding areas, including Kyle, San Marcos, Wimberley and Onion Creek all reported between 11” and 16”. In addition to punishing rain totals, the storm generated three tornadoes and a great deal of property damage.

What made this flood so much more significant than the aforementioned 2013 and ‘15 events? In this case, huge amounts of rainfall were concentrated in a shorter period of time. In addition, the ground in Central Texas was relatively dry prior to this year’s Halloween flood than the months preceding the two earlier events. In dryer conditions, heavy rain doesn’t immediately infiltrate below ground; rather, there is a kind of shock from sudden intense rainfall which results
in surface flow rather than penetration. Potentially-devastating flash floods are sure to follow. 

On the other hand, the Highland lakes saw significant rises in water level, counter to perennial dread about its historical low water levels. Recharge to the Edwards Aquifer hit overdrive, as recharge sites like Anitoch cave (pictured below) submerged.

We recognize that this relief is accompanied by devastation. We’re grateful for the responders who helped evacuate those who experienced this downpour as a disaster. We send care and encouragement to those reeling from yet another assault on their homes and loved ones by extreme flood events.

For information on the response and resources available in Austin and surrounding areas, visit https://www.atxfloods.com.

In the wake of flood events, it may be necessary to take extra precautions like boiling drinking water from your private well. Take a look at https://www.fraserhealth.ca/media/Flood_PrivateDrinkingWater.pdf to find out more.

Friday, October 9, 2015

Texas drying up, despite historic rainfall

Great report on well monitoring and groundwater response to the lack of rainfall, KXAN!

Thursday, October 8, 2015

Barton Springs Flow and Aquifer Levels Turning the Corner.

No drought
Lovelady well height: 517.82
Barton Springs: approximately 91.3 cfs 10-day average

Shorter days and recent temperatures seem to indicate that even cooler temperatures are just around the corner. That’s good news for those who’ve had enough of the Texas summer, but recent weather reports reveal decreasing chances for rain and summer-like weather returning as October continues. According to Bob Rose, LCRA Chief Meteorologist “So far we’ve seen just the opposite kind of weather we typically associate with El Ninos here in Texas.” During the month of September we received a little over 2 inches of rain. That’s 2 more than we saw in the months of July and August combined. Even still, that’s hardly enough to last long in Central Texas and it undoubtedly shows in Barton Springs flow and Edwards aquifer water level, measured at the Lovelady monitor well. We’ve turned the corner from rising aquifer levels and increasing Barton Springs flow thanks to a very wet May, to a downward trend in both. With no recharge and the uncertainty of El Nino-like weather arriving anytime soon this trend will continue. Remember that even as we are not currently in drought, wet conditions in Central Texas rarely last long as the next drought is close around the corner.

Thursday, September 10, 2015

Hoping for Fall falls

No drought
Lovelady well height: 521.69 ft-msl
Barton Springs: approximately 99.3 cfs 10-day average




20150908_TX_trd.jpgAfter 26 inches of heavy rain and flooding in May and June doused Central Texas and recharged the Edwards Aquifer, the landscape broke out in green, floral gratitude. Months later, with barely a trace of additional rain (less than a half-inch in July and August combined), and with heat indices breaking the 110-degree barrier, things are drying out again. By mid-August, much of Central Texas was already considered D0 (Abnormally Dry), with several areas entering D1 (Moderate Drought), according to the US Drought Monitor website. With the majority of Central Texas now in D1 and D2 (Severe Drought) status, the National Weather Service Climate Prediction Center forecasts drought conditions will persist or intensify as we move forward. In just the week from September 1 to 8, the percentage of our state experiencing drought (D0-D4) conditions rose by 5.5%.




For those feeling a sense of déjà vu, we’ve definitely seen this pattern in Texas before. Drought cycles through our state, with at least one period occurring every decade in the 20th century. The Texas Development Board points out that we may be at the beginning stages of a similar trend to one we experienced from 2010-2011, as seen in this image from their article. The percentage of Texas experiencing Abnormally Dry or Drought conditions (D0-D4) in June of 2015 was relatively similar to May of 2010. If the past is repeating itself, we may be looking at an extremely dry time ahead. You can visit the US Drought Monitor to check conditions state and nationwide.


Screen Shot 2015-09-08 at 3.58.27 PM.pngThis year’s historically-strong El Niño may play a role in breaking our dry spell, Mike Halpert, the deputy director of the Climate Prediction Center, told KXAN. The El Niño phenomenon occurs when warming Pacific waters result in above-average rainfall and below-average temperatures, especially in the Southern US (more info here). Then again, John Nielsen-Gammon, the Texas’ state climatologist points out that “the phenomenon can also be kind of a dud in Texas,” citing that “the two most intense El Niños did not produce the greatest amount of rain, and only increased rainfall totals by about 5 percent above normal” (Statesman).


If El Niño does throw some relief our way, we’ll all no doubt be grateful. Regardless, it’s never the wrong time to take action to conserve our most essential natural resource. Dry conditions in August have resulted in low inflows into the Highland Lakes, Buchanan and Travis. The amount of water in the two lakes combined dropped from 78% capacity, 1.56 million acre-feet, on August 1 to 75% capacity, 1.51 million acre-feet, on September 1 (LCRA). Not only do these lakes supply drinking water to more than a million people, they provide critical support to industries, businesses and agriculture along the lower Colorado River basin. We can all do our part to help slow depletion during drought. The EPA, as well as conservation-minded sites like Planetsave.com, provide tips for reducing your personal water use.


Here’s wishing you a cooler, wetter transition into Fall on September 23rd!