Bringing Science to Decision-Making
Updated May 15, 2022
After many years of urging government entities to recognize and monitor the impacts of groundwater pumping on surface waters, Environmental Stewardship has launched a water monitoring project in Bastrop and Lee counties, Texas, to get the work started and inform decisions in the region. Rather than urge and cajole, Environmental Stewardship is taking it up a level. We have purchased state-of-the-art scientific instruments to measure water flow, water chemistry, and well water depth, equipped a mobile laboratory to start collecting data on the current status of surface water-groundwater interaction, and will be providing the field data to decision-makers and the public to enable informed decision-making in the region.
First Demonstration Project – Presidio Lake Study Site
On April 23, 2022, Environmental Stewardship, assisted by interns from one of our collaborators, Green Gate Farms‘ University of Texas intern program, held its first water monitoring event at Presidio Lake Study Site in Lee County, Texas. Presidio Lake is a spring fed reservoir that, according to the landowner and lore, has not stopped flowing for over 100 years … until recently. Two study sites (PLSS-1 and PLSS-2) were established by taking stream flow rate measurements using a state-of-the-art SonTek Flow Tracker 2 instrument. From those two measurements, the study team was able to document that the flow of the Owens Branch of Middle Yegua Creek into- and out-of the lake were 1.3470 and 1.4272 cubic feet per second respectively. Not only were initial flow rates taken to document the current status of the surface water flow, but, in conjunction with geological maps and stratigraphic information, the team was able to make a hypothesis (scientific proposition) about the potential source(s) of the water. Subsequent field data collection will further document the flow, quantify the water chemistry, and test the hypothesis to determine if the source of the water is groundwater, and, if so, what aquifer(s) it is likely derived from.
As the project expands throughout the counties, the use of T-post monitoring gauges will greatly enhance the ability to collect stream flow data. Calibrated aluminum “yard sticks” attached to a t-posts imbedded in the stream will allow landowners to monitor changes in stream flow by making and recording observed water depth when there are observable changes in stream flow (up or down). Stream flow rate (cfs, or cubic feet per second) will be associated with depth measurements over time to provide a “rate curve” for each gauge station, thus providing a method for extrapolating stream flow rate from the calibrated depth measurements. We will solicit landowner participation in this part of the program when we have the primary program up and running and have determined which creeks, streams, springs and/or seeps we need to focus on. For now, there is an urgent issue in eastern Lee County due to the Vista Ridge groundwater pumping just across the line in Burleson County.
With monitoring gauges in streams throughout the counties a great deal of field data can be collected while optimizing use of the FlowTracker instrument. For example, the gauge in the photograph on the left is calibrated to be 1.34 cfs (cubic feet per second) at a stream depth of 13 inches. That is a flow rate of about 600 gallons per minute, which is the rate the landowner confirmed had been estimated by others, further confirming the validity of the measurement. A flow rate of 1.34 cfs is equivalent to 316,113,588 gallons per year, or 970 acre feet per year of water. If this flow is essentially all from groundwater discharging into the stream, it is a significant contribution to the flow of Owens Branch and Middle Yegua Creeks, tributaries to the Brazos River. This is a flowrate that would be very significant in maintaining the ecology of Presidio Lake and the region during drought conditions. Loss of this discharge from groundwater due to non-exempt pumping would be considered an unreasonable impact on surface waters, the environment, the landowners, and the communities that depend on such outflows.
This is clearly a work in progress!
We still have work to do to finish outfitting the trailer so that it is serviceable as a mobile laboratory, preparing an Operations Manual to guide the use of the trailer and equipment, recruiting and training monitoring specialists to use the instruments and equipment , and a list of other work needed to get the project off-the-ground and running. And importantly, we are also in need of donations to help fund an internship/monitoring specialist program to support the field work. If you have an interest in helping with these projects, please contact us so we can discuss how you can help.