Weather Forecast for Texas: Extreme - Part II

Hills, fresh water lakes, rivers and creeks and deep limestone caves make up The Texas Hill Country, an 11-county region in central Texas with diverse terrain. It is an area prone to extreme swings of weather, most notably swings of droughts to flash floods that reoccur over time.

Westward’s resident meteorologist, David Knollhoff, CCM, discussed this weather pattern in his first blog and the connection between weather and water availability in this region of Texas. Our areas water supply remains under constant pressure due to the millions of people living in this region and its continued growth.  One can argue that weather plays an even more critical role on water supply than demand does. Water is the #1 rate limiting factor related to growth and sustainability in our area. This is a major concern to not only officials and scientists, but citizens who recognize we all have a role to play in water conservation.

As just such a citizen, David has volunteered his skills to Cow Creek Groundwater Conservation District (CCGCD), the organization tasked with regulating local water resources in Kendall County, Texas. Kendall County is also Westward’s home office locale and where David and many fellow Westward employees live and work. Not only does David provide pro-bono weather forecasts, drought outlooks and rainfall analyses, but he is spearheading a local citizen science weather study to combat drought mitigation in order to help the district develop a tool for their water use restriction decisions and policies.

When addressing the huge issue of water availability and restriction decisions, the following initial questions arise:

• What percentage of rainfall occurring in the area is reaching the local aquifers underneath Kendall County as recharge? Is 10%, 5% or 1% of rainfall leading to recharge? 

• What does the variance of recharge look like across the county for different rainfall rates in coverage and time? 

• How can the variances be connected to our weather patterns? 

• Are the variances predictable? 

• Should the variances and prediction of variances even be an important aspect to the decision-making process by the district? 

While we do not know exact percentages or variances related to aquifer gains, we suspect it is around 4 percent on average in a 12-month period, at least locally, according to Report 353 by Texas Water Development Board.

In addition to studies from the Texas Water Development Board, volunteers from the Community Collaborative Rain, Hail & Snow (CoCoRaHS), a national, grassroots volunteer network of weather observers, document how much rainfall occurs on a daily, monthly and annual basis through its interactive website.

Below is an example of daily rainfall amounts (measured with a precision to the hundredths of an inch) across Kendall County on April 23, 2020, via reports submitted to the CoCoRaHS network:

So as you can see, we have good intelligence of rainfall precipitation in the county. However, to be able to answer the questions listed above, we need to gather a better understanding of how much water is evaporating and transpiring back into the atmosphere near ground level during the same timeframe as when it rains.

Data is a meteorologist’s best friend, so David suggests the team study evapotranspiration (ET)—the process of transferring moisture from the earth to the atmosphere via water evaporation and transpiration from plants. So currently the team is placing a total of three ET gauges across Kendall County that measure evapotranspiration and report the daily values to CoCoRaHS, which is building a database of ET amounts across space and time. 

Observations of ET are necessary to grasp a better understanding of the potential amount of rainfall hitting the ground that is not available to contribute to recharge. On average an ET gauge costs approximately $300.

The goal of the study is to expand the rainfall recording program by asking 900 more citizen scientists and weather enthusiasts in Kendall County to measure and submit daily rainfall data through cocorahs.org. Participation in this activity requires the purchase of a $40 rain gauge.  Even if there is no measurable rainfall, a zero or trace value submitted on a daily basis is desired and encouraged but not required.  Training on how to measure and submit the information is provided when requested by the observer.  Currently we have nearly 25 people reporting daily throughout the year in Kendall County. This type of long-term data collection in conjunction with learning more about how much water is not contributing to groundwater recharge will give our area a much more comprehensive picture of how to plan for and tackle current and future water issues.

Want to get involved? Contact Dave Knollhoff via email at dknollhoff@gvtc.com or call (830) 249-8284.