Pumping Influence In Central Texas Trinity Aquifer Revealed In Real Time

Figure 3

The Comal Trinity Groundwater Conservation District is employing Wellntel technology to create a cost-effective and powerful groundwater-monitoring network that will greatly increase hydrogeologic understanding and science-based resource management. Their network build-out began in October 2018 with 4 wells, scaling to 10 in early 2019.

“The plan to establish monitoring wells in the Trinity Aquifer has been accelerated since the expense is much less than anticipated with the application of the Wellntel product” said Larry Hull, Board President, Comal Trinity GCD.

In Comal County, Texas are two near-by residential wells completed in the same aquifer within the Trinity Group. During 2019 the changes in groundwater level in these two wells have tracked very closely as seen in the composite hydrograph of Figure 1, rising about 3 1/2 feet in January and then exhibiting a gradual decline of about 7 feet during February through April. The first two weeks of May have seen a rise of about 4 feet.

The hydrograph also shows every occurance of pumping in these two wells, recording the depth to water at Pump Start, Pump Stop, and then through each following defined Well Recovery period. Pumping drawdown has typically been about 12 to 14 feet. All of these data – both timed and pumping measurements – are provided to network sponsors and managers in real time through the Wellntel Analytics Dashboard.

Of particular interest is a period at the end of April during which the well represented by the blue hydrograph was pumped repeatedly over about 25 hours. The pumping events are not individually distinguishable when the entire data set is plotted, but are visible in the closer view when zooming tools are used, as shown in Figure 1.

Figure 1

The Wellntel sensors for both these wells were set to collect measurements during every pumping event and, when not pumping, timed measurements were on a 4-hour interval. In order to see the hydrologic influence of the extended pumping period on both the pumping well and the neighboring well (red hydrograph)the timed measurement interval was shortened to 10 minutes. This change would have the added benefit of collecting Pump Run depth-to-water measurements since pumping duration is typically shorter than the previously set 4-hour interval.

The active telemetry that is standard with the Wellntel platform made it possible to remotely change the measurement interval for both of these wells. The change was made for the pumping well near the beginning of the pumping period and for the neighboring well about midway through the pumping period. The time during which the 10-minute measurement interval was set for each well is noted on Figure 2.

Figure 2

The influence of the pumping over time is clearly seen for the pumping well in both its non-pumping level and the depth of drawdown. And a related lowering of the water level is seen in the neighboring well. The relation between the cumulative discharge over this pumping period and the quantified response of the aquifer seen in both hydrographs will contribute to the understanding of the aquifer characteristics – such as hydraulic conductivity and storage properties – in Comal County.

A closer look at the data is provided in Figure 3, revealing the significant hydraulic connection that exists in the aquifer between the pumping well and the neighboring well. Once depth-to-water measurements were being collected on a 10-minute interval, the data in the neighboring well (red hydrograph) clearly demonstrate falling water levels during periods of pumping and rising water levels when the pump is off.

Figure 3

The collection of these data is made possible by Wellntel sensor technology that turns submersible pump wells into monitoring points, that tags depth-to-water measurements as timed or relating to pumping activity, and that provides data in real time for action by well owners, network sponsors, or resource managers.  

According to Mr. Hull, “Wellntel’s monitoring system and associated analytical tools have provided real time data across the diverse hydrology within the Trinity Aquifer.”

We look forward to a continuing collaboration with the Comal Trinity GCD to provide important insights – such as groundwater flow dynamics, spatial distribution of recharge, and hydraulic gradients between major aquifers – that the dense data collected from a well-designed network can provide.