Research
Mark Person, Professor of Hydrology
Research
Mark Person, Professor of Hydrology
My research is currently centered on five topics:
Most of these topics consider groundwater flow deep within the Earth’s crust and must consider a variety of fluid flow impelling mechanisms, shown at right. A lot of these projects involve field work. I try to involve both graduate students and undergrads in all of my field campaigns.
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Above: Mark Person labels carbon 14 bottles for age dating of groundwaters from the Roer Valley Rift, Germany. The sampling truck was provided by Erftver-band and contains 2 on board groundwater pumps. |
Above: Graduate Student Yao You and Mark Person collect temperature profiles along a fault zone within the Roer Valley Rift, Germany. Temperature anomalies help to establish whether groundwater is moving up fault. |
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| 1. Climate Change Hydrogeology. During the last 2 million years, average annual temperatures have varied by as much as 6°C across North America. There have been equally dramatic shifts in precipitation intensity (as much as 50% in some places). In coastal regions, sea level has varied by as much as 120 m in response to the waxing and waning of ice sheets. One theme of my research has been to try to understand how past climate fluctuations have influenced groundwater flow patterns, recharge rates, and the distribution of freshwater resources. We have recently completed three NSF-funded projects to look at how Holocene/Pleistocene climate changes subsurface flow systems. One of these studies has focused mid-Holocene (3-7 thousand years before present) hydrogeologic changes within glaciated regions of the Midwestern USA (Crow Wing–Murray Basin Project). Using pollen data collected from lake cores, we found that this time period was about 4-6°C warmer and had about half the precipitation of today (not so different from the worst case scenarios predicted by global climate models Minnesota, 2050). There we found that water table and lake levels dropped by as much as 15 m during the mid-Holocene warm/dry periods (think of what that would do to lake front real estate!). We completed a similar study within the Murray Basin, Australia, with Professor Jeffery Hanor. We found a similar (albeit more dramatic) response to Quaternary Climate within the Murray Basin, Australia. Lake records and our paleohydrologic model reconstructions suggest that the water table fluctuated by up to 50 meters due to Quaternary climate cycles (Crow Wing–Murray Basin Project). I like to think that this could provide valuable insights into what future water resources conditions might look like in response to atmospheric CO2 doubling projected for the next 50 years. I currently have an NSF project to study the role of ice sheets on freshwater resources of the Illinois Basin with Jennifer McIntoh at the University of Arizona. The Illinois Basin was over-run by the Laurentide Ice sheet during the last glacial maximum. As the ice sheet melted and retreated, we have found evidence that recharge rates increased by as much as 10 fold where the ice sheets over ran recharge areas. This resulted in the emplacement of large quantities of freshwater within confined aquifers like the Mt. Simon sandstone over a relatively short time period of time (4000 years). | ||
| 2. Basin-Scale Hydrogeologic Modeling. I spend a lot of my time developing numerical models to study groundwater flow problems at the sedimentary basin-scale in order to reconstruct paleohydrogeologic conditions. My students, collaborators, and I have developed both cross-sectional and three-dimensional hydrologic models to study the paleohydrology of sedimentary basins. In the 1990s I developed RIFT2D, a two-dimensional basin model that can be used to study the evolution of groundwater flow systems within rift basin on geologic time scales (107 years). We applied this model | ||
| to the Rio Grande Rift in order to study the evolution of groundwater flow patterns through geologic time and to determine the controls of groundwater flow on potassium metasomatism of tuff units with Shari Kelly and Nelia Dunbar at New Mexico Tech (Rio Grande Rift Project Page). More recently, I have been involved in developing basin-scale groundwater flow models in three-spatial dimensions to study the paleohydrology of the Atlantic Continental Shelf in New England (Nantucket Project). In collaboration with Dr. Peng Wang at Indiana University and Dr. Denis Cohen and Iowa State University, we developed PGEOFE (Parallel GEOlogic Finite Elements) to run on massively parallel computers using the AZTEC solver package from Sandia National Laboratory. A special feature of this code is its ability to represent Pleistocene sea level fluctuations and the waxing and waning of ice sheets (Nantucket Project; slides 36-40). With support from the NSF Teragrid project, we have been running PGEOFE on Indiana University’s massively parallel supercomputers BigRed. |
Above: Big Red is one of the most powerful university-owned computers in the US, and one of the 50 fastest supercomputers in the world. Big Red has achieved more than 21 teraflops on numerical computations. Big Red is a distributed shared-memory cluster, consisting of 768 IBM JS21 Blades, each with two dual-core PowerPC 970 MP processors, 8GB of memory, and a PCI-X Myrinet 2000 adapter for high-bandwidth, low-latency MPI (Message Passing Interface) applications. |
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| I anticipate using this model to study a wide range of hydrogeologic problems in the near future. For example, within much of the southwestern USA, water extractions are occurring at rates that are not sustainable. Over-pumping can lead to diminished surface water resources, upcoming of saline groundwater, and land subsidence. There is a pressing need to predict water quantity and quality as well as safe aquifer yield within regional aquifer systems on decadal time scales. In addition, the US Department of Energy is considering sequestering millions of metric tons of CO2 from coal-fired power plants into deep oil reservoirs and saline aquifers. There is also a need to understand what are the environmental impacts of CO2 sequestration on shallow hydrologic systems. Basin-scale mathematical modeling represents a powerful tool for understanding the connections between these deep and shallow subsurface regimes. These problems require novel computer models that can represent long-term changes in water-table levels in response to pumping, surface water-groundwater interactions. PGEOFE is a basin-scale numerical model that can represent geologic complexities such as faults, sedimentary heterogeneity (Zhang et al. 2006), and sedimentary unit pinch outs using finite element methods. | ||
| 3. Groundwater in Geologic Processes. Groundwater plays an important role in the formation of metal ore deposits and oil generation/migration. Because groundwater can modify the subsurface temperature patterns, oil generation (a temperature dependent process) occurs at greater depths within recharge areas of continental sedimentary basins (e.g., the Rhine Graben, Person and Garven, 1992) relative to discharge areas. Groundwater flow patterns can also influence the pathways oil migrates through sedimentary basins (Bekele et al., 1997; 2002). Groundwater discharge, especially along faults, can form hot springs and ore deposits. I have been working with Dr. Al Hofstra of the US Geological Survey in Denver for the past 5 years trying to understand how groundwater flow patterns within the Great Basin, Nevada, formed the world class Carlin Gold Deposits (Person et al., 2007, submitted, Geosphere; Carlin Project). | ||
| 4. Geothermal Systems. I have been studying the Coso Geothermal System within Eastern California during the past 3 years. With support from the US Department of the Navy, we have tried to understand the hydrologic consequences of geothermal power production on water resources and hot spring activity at China Lake, California (Person et al. 2007). China Lake hosts the Coso geothermal system which produces about 270 Mw of geothermal power each year. We have tried to evaluate the hydrologic consequences of geothermal power development on Coso Hot springs (Coso Project Link). We hope to continue work looking at the plumbing of Coso Hot Springs in the future. We are interested in understanding the depth of groundwater circulation within other Great Basin geothermal systems such as Beowawe. A proposal to study the Beowawe Geothermal system will be submitted to the NSF Hydrologic Sciences Program in December 2007. | ||
| 5. Fault Hydrogeology. Faults can play a major role in controlling regional groundwater flow patterns within sedimentary basins. Within many fault controlled basins, such as the Rio Grande Rift, large water table drops occur across faults suggesting that they act as barriers to lateral flow. However, we have collected compelling geochemical and thermal data which suggests that these faults can also act as vertical conduits for upwelling groundwater. Along with my former postdoc (Dr. Victor Bense) we have been developing a new quantitative model of fault permeability within continental rift basins (Bense and Person, 2006). With support from NSF, we have been trying to test our new fault permeability model within the Roer Valley, Germany. This is perhaps the best field area in the world to study shallow (< 500m) fault permeability (Roer Valley Project). This past summer, we deep collected temperature profiles and measured noble gas and environmental isotope composition of groundwaters across fault zones along the Roer Valley Rift. The idea is to see if these fault zones produce thermal anomalies or act as conduits for old, geochemically evolved groundwaters. We hope to return next summer (2008) to complete out field sampling. We have also begun to develop RIFT3D in order to study fluid flow (oil and water) and fault permeability evolution over geologic time scales. | ||
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