Abstract Details
(2020) Multi-Component Geochemical Characterization to Support Hydrologic Modeling in an Urban Aquifer System, Fountain Creek Alluvial Aquifer, El Paso County, Colorado
Newman C, Baker E, Paschke S & Kisfalusi Z
https://doi.org/10.46427/gold2020.1915
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13e: Room 4, Thursday 25th June 08:24 - 08:27
Connor Newman
Emily Baker
Suzanne Paschke
Zachary Kisfalusi View abstracts at 2 conferences in series
Emily Baker
Suzanne Paschke
Zachary Kisfalusi View abstracts at 2 conferences in series
Listed below are questions that have been submitted by the community that the author will try and cover in their presentation. To submit a question, ensure you are signed in to the website. Authors or session conveners approve questions before they are displayed here.
Submitted by Kip Solomon on Monday 22nd June 23:04
Thank you for your presentation. I'm wondering if you examined the relationship between apparent age and distance from the waste water source versus apparent age versus depth below the water table? If most of the groundwater recharge is coming from near the waste water source then it seems like ages should vary with distance whereas if most of the groundwater recharge is coming from aerially distributed infiltration of precipitation, then the ages should vary more with depth than with distance. Thank you.
Hello Kip, that is an excellent question. When we look at wells completed near the creek (the same wells that have high Gd-anomaly as noted in my presentation) we see that they have a relationship of increasing age with increasing distance from the waste water treatment plant, and that the older groundwater in these wells is also found where the water table is deeper. This may suggest that a combination of infiltration of waste water effluent and aerially distributed recharge are responsible for recharge in this zone of the aquifer. When we look at all the wells throughout the study area (across the three hydrochemical groups I discussed in the presentation), then we see there is not a strong relationship of age with depth to the water table. Unfortunately, the oldest groundwater in our study (~25 years old) is from a well where we could not determine the depth to water (the well can be sampled from an outlet but the cap cannot be opened to use a water-level tape). This well would have been good to include in the analysis of water table depth. I have made a figure that shows these relationships which can be viewed on my Google Drive, https://drive.google.com/file/d/1wOSOTV17hgMTR9S82ToUcdVwtnnFqAeL/view?usp=sharing Thanks for the question!
Thank you for your presentation. I'm wondering if you examined the relationship between apparent age and distance from the waste water source versus apparent age versus depth below the water table? If most of the groundwater recharge is coming from near the waste water source then it seems like ages should vary with distance whereas if most of the groundwater recharge is coming from aerially distributed infiltration of precipitation, then the ages should vary more with depth than with distance. Thank you.
Hello Kip, that is an excellent question. When we look at wells completed near the creek (the same wells that have high Gd-anomaly as noted in my presentation) we see that they have a relationship of increasing age with increasing distance from the waste water treatment plant, and that the older groundwater in these wells is also found where the water table is deeper. This may suggest that a combination of infiltration of waste water effluent and aerially distributed recharge are responsible for recharge in this zone of the aquifer. When we look at all the wells throughout the study area (across the three hydrochemical groups I discussed in the presentation), then we see there is not a strong relationship of age with depth to the water table. Unfortunately, the oldest groundwater in our study (~25 years old) is from a well where we could not determine the depth to water (the well can be sampled from an outlet but the cap cannot be opened to use a water-level tape). This well would have been good to include in the analysis of water table depth. I have made a figure that shows these relationships which can be viewed on my Google Drive, https://drive.google.com/file/d/1wOSOTV17hgMTR9S82ToUcdVwtnnFqAeL/view?usp=sharing Thanks for the question!
Submitted by Rolf Kipfer on Wednesday 24th June 14:42
Dear Connor Congratulations for your herculean effort on integrate all those hundreds of hydro-geochemical parameters into a groundwater model. If I understood you correctly, you finally used tracer data to improve the conceptual basis of your groundwater model. Please, can you elaborate on your experience about the value of tracer data in ground water modelling and when during the process of model development tracer data return the most benefit? And, against what kind for information you finally validated your model (heads, tracer, transit times, ...)? With best regards - Rolf Kipfer (RoKi)
Hello Rolf, thanks for your question and this is an important aspect that I try to discuss with the organizations that fund my work. With regards to the value of tracer data, I find these datasets to have a conceptual value far greater than their monetary costs (and they are not necessarily cheap). The information gained from understanding a system from a geochemical viewpoint as opposed to only a physical hydrologic viewpoint can be the difference in a constructing a useful model or not. For this project in particular, we have numerous heads to calibrate our groundwater flow model to, but it would be possible (if not likely) to calibrate a highly flawed model using head-data alone because the hydraulic properties vary across four orders of magnitude within the study area (as evinced by aquifer testing) and because the recharge rates in the area have not been rigorously quantified by previous studies. To the second part of your question, I prefer to have a variety of tracer data early on in the project while the numerical model development is still in its infancy. That way, we have lots of time to test various boundary conditions and we have direction from the geochemical data while there is still project time and budget to consider all the possibilities. Finally, the model is currently being calibrated just against heads but once that calibration is complete we will also calibrate to observed tracer concentrations and advective travel times using particle tracking. One of the things that will be interesting to see is how much the calibration changes after we quantitatively include the tracer data (i.e., after the purely head-based calibration). That will be where the use of the tracer data really shows itself I think. Thanks for the discussion!
Dear Connor Congratulations for your herculean effort on integrate all those hundreds of hydro-geochemical parameters into a groundwater model. If I understood you correctly, you finally used tracer data to improve the conceptual basis of your groundwater model. Please, can you elaborate on your experience about the value of tracer data in ground water modelling and when during the process of model development tracer data return the most benefit? And, against what kind for information you finally validated your model (heads, tracer, transit times, ...)? With best regards - Rolf Kipfer (RoKi)
Hello Rolf, thanks for your question and this is an important aspect that I try to discuss with the organizations that fund my work. With regards to the value of tracer data, I find these datasets to have a conceptual value far greater than their monetary costs (and they are not necessarily cheap). The information gained from understanding a system from a geochemical viewpoint as opposed to only a physical hydrologic viewpoint can be the difference in a constructing a useful model or not. For this project in particular, we have numerous heads to calibrate our groundwater flow model to, but it would be possible (if not likely) to calibrate a highly flawed model using head-data alone because the hydraulic properties vary across four orders of magnitude within the study area (as evinced by aquifer testing) and because the recharge rates in the area have not been rigorously quantified by previous studies. To the second part of your question, I prefer to have a variety of tracer data early on in the project while the numerical model development is still in its infancy. That way, we have lots of time to test various boundary conditions and we have direction from the geochemical data while there is still project time and budget to consider all the possibilities. Finally, the model is currently being calibrated just against heads but once that calibration is complete we will also calibrate to observed tracer concentrations and advective travel times using particle tracking. One of the things that will be interesting to see is how much the calibration changes after we quantitatively include the tracer data (i.e., after the purely head-based calibration). That will be where the use of the tracer data really shows itself I think. Thanks for the discussion!
Submitted by Rolf Kipfer on Wednesday 24th June 17:32
Dear Connor Congratulations for your herculean effort on integrate all those hundreds of hydro-geochemical parameters into a groundwater model. If I understood you correctly, you finally used tracer data to improve the conceptual basis of your groundwater model. Please, can you elaborate on your experience about the value of tracer data in ground water modelling and when during the process of model development tracer data return the most benefit? And, against what kind for information you finally validated your model (heads, tracer, transit times, ...)? With best regards - Rolf Kipfer (RoKi)
Dear Connor Congratulations for your herculean effort on integrate all those hundreds of hydro-geochemical parameters into a groundwater model. If I understood you correctly, you finally used tracer data to improve the conceptual basis of your groundwater model. Please, can you elaborate on your experience about the value of tracer data in ground water modelling and when during the process of model development tracer data return the most benefit? And, against what kind for information you finally validated your model (heads, tracer, transit times, ...)? With best regards - Rolf Kipfer (RoKi)
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