Break-out Group Discussion of Faults
2nd Annual Española Basin Workshop
March 5, 2003
Notes prepared by
Jonathan Caine, U.S. Geological Survey, Denver,
and Mick Nickel, Pueblo of Tesuque
Answers and Thoughts on the Focus Questions
- What research is ongoing?
Analog Studies in the Albuquerque Basin
- Identification of buried faults using high-resolution aeromagnetic data.
- Detailed mapping, characterization, rock-hydraulic properties and geochemistry of fault and host rocks in a well-exposed analog fault zone in the Santa Fe Group.
- Regional characterization of different types of faults in different host lithologies.
- Numerical flow modeling of the impacts of faults using water level and InSAR data.
- What are the major gaps in knowledge?
- Detailed information (best if not from drillers) on static water levels from wells, water usage, and water well flow data, and local geologic data.
- Styles and types of fault and fault rocks in the different major lithologies found in the basin and how they vary from the local to the regional scale.
- Impact of heterogeneity of faults on the groundwater supply in both a temporal and spatial sense.
- What is the regional to local scale geologic framework of the flow system?
- How are faults and fault properties best incorporated into numerical models?
- Analysis and evaluation of existing data on faults in order to rank and order them in terms of degree of strategic impact.
- Geochemistry data is biased on the west side of the basin – need data from the east side.
- Identify and focus on locations where aquifer stresses are occurring or may occur in the near future
- Analogs for Espanola are not well described.
- What new data are needed to fill the knowledge gaps or refine what we do know?
- Establishment of water wells that can be used to get synoptic water level data particularly in the vicinity of faults and where the aquifer system is being stressed
- Determine and evaluate the role fault zones play as potential pathways for deep aquifer recharge.
- Need more robust basin-wide geochemistry and basin age information.
- Evaluation of the unsaturated zone and how faults might behave differently there than in the saturated zone (J. Sigda and LANL doing some work but need more).
- Need a better understanding of the relationships between drawdown of different types of aquifers from alluvium to Santa Fe Group to bedrock.
- There is a baseline gap in seismic data from the west side to the east side of the basin where most data is in the west.
- Need for better data on recharge mechanisms, water ages, circulations depths, ET measurements, watershed modeling, and mountain block water levels and how these things might be influenced by faults or not.
- How do we best move forward to achieve our goals?
- Continued identification of buried faults using high-resolution aeromagnetic data.
- Evaluate what geological controls affect the groundwater flow system and learn how to model them using predictive, numerical flow models.
- Identify where faults are by new mapping and use of geophysics, evaluate what their hydraulic properties are, conduct aquifer tests in the vicinity of faults, use dedicated water level measurements in wells impacted by faults, measure the chemistry of fault rocks and groundwaters impacted by faults as a way of having a physical tracer of the impacts of faults.
- Identify critical areas (Embudo was suggested), based on an agreed upon set of criteria, of heterogeneity to do detailed sampling, characterization, and analysis to lead toward future ability to forecast behavior of faulted aquifers. First step should be based on fault rock properties and geometries and should be well integrated with direct observation of behavior of groundwater impacted by faults.
- Create a set of testable hypotheses, test them, then analyze the uncertainty associated with the results to help forecasts be more probabilistic rather then deterministic. These hypotheses must evolve and become refined as we learn more. This approach will help prioritize many of the complexities and variables that make this a difficult problem to address.
- Drill deep wells on east and west side of Pajarito fault as a potential detailed study site.
- Analyze and interpret model results and hypotheses test results to define and refine most important parameters of fault related fluid flow in the aquifer system.
- Pattern recognition through well-known data points.
- Correlate locations undergoing aquifer stress with known or to be determined locations of faults.
- Compare various fault data to pinpoint similarities and differences.
- Identify contaminant plumes that might be impacted by faults or contaminant plume geometries and travel times that might reveal previously unknown faults.
- Other comments and questions
- What are the current and potential future economic impacts of faults from their influence on the aquifer system?
- Faults are considered by some to have no impact in the basin. However, this is a regional perspective and there is significant evidence that they have a very large impact at the scale of a well field. Additionally, the way in which aquifer stresses occur (e.g., well pumping rate and duration) may also exacerbate the impact of faults.
- USGS, WRD, Albuquerque is in process of selecting locations for piezometer nests for monitoring groundwater in the Española Basin and these could be targeted in areas near faults and that have significant stresses associated with the local aquifer.
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