home > research > project descriptions
My research focuses on physical and chemical hydrogeology on land and below the seafloor. My research group and colleagues have completed projects focusing on groundwater recharge, surface water - groundwater interactions, the upper oceanic crust at seafloor spreading centers and on ridge flanks, heat flow below the West Antarctic Ice Sheet, and numerous additional problems. We use mapping, seismic, borehole, and thermal data, measure seepage fluxes, collect and analyze water and soil samples, and simulate hydrologic processes using numerical and analytical models.
Recent highlights include: (1) development of numerous projects involving the influence of environmental change on groundwater and surface water systems, including establishment of The Recharge Initiative and the UC Water Security and Sustainability Research Initiative (UC WASSRI, aka, UC Water); (2) a successfull first phase and renewal for the second phase of an NSF Science and Technology Center, the Center for Dark Energy Biosphere Investigations (C-DEBI), (3) development of novel tools and the first successful measurements of the heat flux into the base of the West Antarctic Ice Sheet, as part of the WISSARD project. These and other projects include field work, laboratory analyses, and modeling. Read about this work in the brief summaries below, and/or follow the link below to abstracts and publications.
Interested in terrestrial hydrogeology/hydrology projects?
Interested in subseafloor hydrogeology projects?
Please see below and contact me for more information.
Research Projects in Hydrogeology on Land
Research Projects in Marine Hydrogeology
Thinking about joining the UCSC Hydrogeology research group?
The project on land that occupies much of my time these days involves development of tools and methods to help managed aquifer recharge (MAR) so as to simultaneously benefit both water supply and water quality objectives. Enhancements to water supply will help to reduce groundwater overdraft, contributing to reductions in the extent of subsidence, seawater intrusion, upflow of lower-quality water from depth, loss from critical surface reservoirs (including streams, lakes, and wetlands), and associated damage to fragile and valuable ecosystems. MAR operations can be run as part of a regional conjunctive use strategy, generating significant benefits to water managers, regulators, stakeholders, and aquatic ecosystems by shifting resource use patterns on the basis of (often unpredictable) availability; this characteristic will become increasingly important in coming decades as climate changes force modification of resource availability and use patterns. Many studies of MAR systems have focused on physical aspects of their operation, particularly causes and impacts of clogging. In contrast, our work focuses on quantitative reduction to nitrate loads during MAR. Improvements to water quality during MAR operations have been documented in a few cases, but this study is unique in combining evaluation of MAR operation with quantitative reductions in nitrate load. We are completing this work in several locations, including as part of the Harkins Slough MAR project, developed and operated by a local water agency. The project design includes extraordinarily strong control on system mass balance (water, solutes), applies novel technologies and techniques, and provides unique opportunities to link water supply and water quality objectives, and to quantify relations between processes, properties, and MAR. The project comprises a newly-developed collaboration between a local water agency and additional colleagues working at the USGS, Moss Landing Marine Laboratory, University of Alaska Fairbanks, Californina State University - Monterey Bay, and involve numerous graduate and undergraduate student researchers. Current GSRs working on these projects include: S. Beganskas, G. Gorski, and E. Teo. Earlier UCSC GSRs were C. Schmidt, A. Racz, and T. Russo.
Harkins Slough MAR location map and cartoon showing experimental design:
C. Geoff Wheat (UAF) hold a OsmoSampler system prior to installation in a groundwater monitoring well. Graduate Student Researcher, Calla Schmidt (UCSC), and project co-PI, Marc Los Huertos (CSUMB and UCSC) conduct a soil survey and collect samples from the base of the pond during the dry season.
 |
 |
To the left is the Harkins Slough percolation pond during the 2007-08 recharge season. The pond is not completely full - flat area in the distance can also be covered. Calla Schmidt in full field regalia for sampling of recharge to assess water quality. Calla has done great work on this project, and you can some of her recent publications in peer-reviewed journals here: Schmidt et al., 2011a, Schmidt et al., 2011b.
 |
 |
This figure shows the nitrate load reduction during MAR, calculated by combining water quality and infiltration data. We see about 50% load reduction during the first meter of infiltration, a load reduction that is commensurate with that achieved with vegetative buffer strips.
Interestingly, we see an increase in the rate of denitrification with increasing infiltration rate, until we hit a threshold of about 0.6 to 0.8 m/day. At rates higher than this, oxic conditions penetrate to depth throughout the saturated zone (above an inverted water table), and denitrification becomes less energetically favorable.
Graduate student Andrew Racz has been mapping patterns of infiltration below the pond and associated diffrences and changes in soil hydraulic properties using a thermal method developed by UCSC Hydrogeology alumna Dr. Christine Hatch, as part of her dissertation. Here is Andrew holding up some of the sensors we use for applying this method:
A paper describing our application of this method, including the discovery that infiltration during MAR sweeps across the recharge pond like a wave, can be found in Racz et al., 2011.
 |
 |
This figure shows how much infiltration rates vary spatially and temporally during a single season of MAR operations. The region of the most rapid infiltration sweeps across the pond at a lateral rate of about 2 m/day. Our studies also documented order-of-magnitude changes in saturated hydraulic conductivity within shallow soils
Tess Russo and colleagues recently completed an amazing study of surface water - groundwater interactions during controlled flooding of the Tuolumne River, Yosemite National Park. This is a field, lab and modeling study that was put together in a hurry, and on a limited budget, involving difficult work in a remote field area (Poopenaut Valley). A resulting paper is now in review in J. Hydrology, Russo et al., 2011.
Tess also completed an interesting study of changes in extreme precipitation around the SF Bay area, repeating an classic analysis done by S. Rantz of the USGS in 1971, and adding statistical rigor (using a Monte Carlo analysis) to evaluate whether the patterns of extreme precipitation seen today are part of the "same data set" as those seen 50+ years ago (Russo et al., 2013). The bottom line? Conditions have changed. Big time. Here is an example:
What used to be 50-yr, 10-day storm during the first half of the 20th century is now a 12-yr, 10-day storm. There are similar patterns for all depth-duration pairs studied. This is sobering, and it requires that planners, water managers, growers, engineers and others recalibate their expectations for extreme precitpitation. This also is likely to mean less natural groundwater recharge, paticularly when climate change is combined with changes in land use.
Another of Tess's studies (about to be submitted for peer reviewed publication) assesses regional suitability for managed aquifer recharge. This diagram summarizes one of the key results:
This analysis is based on eleven spatial data coverages, and helps to identify locations where MAR might help to improve water resource conditions. We also designed and built a percolation testing system, for use in field studies:
We have deployed this system at three field locations so far, and Sarah Beganskas is working with data to assess vertical versus lateral flow during testing, and what this can tell us about the layering of hydrologic properties in shallow soils.
Another recent project was a multidisciplinary study of the dynamics and impacts of surface water - groundwater interaction in the Pajaro Valley, central coastal California. This effort grew out of discussions and observations while I was serving on Technical Advisory Committees for two local water districts, a nice illustration that there can be positive links between service and research. Although surface water and groundwater are increasingly understood to comprise a single resource, and the movement of water between surface and ground reservoirs is extremely sensitive to factors such as groundwater pumping, stream discharge control, and seasonality and climate change, there is very little information available on factors controlling stream seepage: where it occurs, how variable it is throughout the water year, and how it influences available water quantity and quality. One reason for the lack of data is the difficulty of measuring associated properties and processes in a continuous way. I recruited two graduate students, C. Hatch and C. Ruehl, secured a small grant from the UCSC Committee of Research, and we gathered sufficient data and understanding of the literature to write a successful grant proposal for a more complete project. funded through the U.S. Department of Agriculture's National Research Initiative. This project ran through Summer 2007, ultimately supporting four graduate students and 11 undergraduate student researchers. We also received equipment and field support from the City of Watsonville and in-kind, office, and field support from the Pajaro Valley Water Management Agency, and a grant for isotopic analyses from the UCSC STEPS program. This project is a collaboration between members of the agencies listed above, the USGS., the University of Alaska Fairbanks (Moss Landing campus), and UCSC's Center For Agroecology and Sustainable Food Systems and the Environmental Studies Department. As of Fall 2008, three papers have been published describing results of this project, and first-authored by former students. Additional manuscripts are in progress.
Please see the Publications page for documents describing earlier research projects, including a study of model of mass, energy, and oxygen budgets in a coastal estuary, benthic seepage and its possible impacts on metals contamination in San Francisco Bay, aquifer characterization and the history of regional uplift at former Fort Ord, and aquifer characterization in Pennsylvanian bedrock aquifers in Indiana.
My research group has been involved with several studies of hydrothermal activity on the eastern flank of the Juan de Fuca Ridge, northeastern Pacific Ocean. I sailed to this area as a co-chief scientist on Ocean Drilling Program (ODP) Leg 168 (1996), and as chief scientist of a site survey expedition to prepare for future drilling and experiments (RetroFlux expedition, 2000). The latter program was coordinated with a simultaneous expedition to collect swath map and seismic data (ImageFlux expedition, 2000; chief scientist: V. Spiess, U. Bremen). Studies resulting from these expeditions comprised parts of theses and publications by four UCSC graduate students (J. Stein, E. Giambalvo, G. Spinelli, M. Hutnak). These studies have included in-situ and laboratory permeability tests; comparisons of permeability, heat flow, and seismic data; analysis of large-scale thermal patterns to resolve fluid flow directions and intensity in basement; and computer modeling in which heat flow data, pore-fluid pressures, fluid chemistry, lithostratigraphy, and other data are used to constrain crustal properties. Numerical studies with Stein, Spinelli, Giambalvo, Hutnak, and Winslow have developed the concept of the hydrothermal siphon as a mechanism for driving massive amounts of hydrothermal fluid through the crust, have shown the importance of the permeability distribution (as opposed to a single bulk value) in guiding flow, and indicate that transient models with well-constrained initial conditions are required to determine fluid flow directions. This work has led to reassessment of many studies and interpretations made during the last several decades. Laboratory work and modeling with Spinelli and Giambalvo has shown the importance of small-scale variations in sediment type and thickness in controlling seafloor hydrothermal seepage, a surface manifestation of underlying convection. Observational work and analytical models published with Hutnak and others have revealed the importance of seamounts in guiding hydrothermal recharge and discharge, helping to resolve a long standing conundrum in global thermal studies: how a large fraction of lithospheric heat is mined from oceanic crust once tens of meters of sediment accumulate across large areas. One set of these results is summarized in the figure that follows. Current GSR E. Adelstein is working on the next generation of three-dimensional models, and postdoc, T. Weathers, is exploring coupled flows that can support microbes in the deep biosphere.
 |
 |
Heat flow data were collected adjacent to two basement outcrops on 3.5 Ma seafloor (Fig. A). Heat flow rises abruptly from regional background values adjacent to a discharging outcrop (Baby Bare; Fig B), and drops abruptly adjacent to a recharging outcrop ~50 km to the south (Grizzly Bare, Fig C). Analytical calculations show that hydrothermal circulation between these outcrops can be driven by a "hydrothermal siphon" that sustains fluid flow on the basis of pressure differences between recharge and discharge sites. Numerical calculations show that fluid fluxes consistent with independent estimates are sufficient to match seafloor heat flow and basement temperature patterns, and require effective basement permeabilities on the order of 10-11 to 10-10 m2.
A drilling proposal for which I was lead proponent (with 19 co-proponents from four countries) was selected for the first expedition of the Integrated Ocean Drilling Program (IODP, the successor program to ODP) Expedition 301, June-August 2004, and I served as co-chief scientist (with T. Urabe, U. Tokyo). The complete project includes two drilling expeditions (one being Expedition 301, the other to be scheduled in 2009/10) and a series of submersible and remotely-operated vehicle operations, all in support of hydrogeologic and related experiments. The complete project includes two drilling expeditions and a series of submersible and remotely-operated vehicle (ROV) expeditions, all in support of hydrogeologic and related experiments. The multidisciplinary observational, experimental, and modeling program is designed to evaluate the formation-scale hydrogeologic properties within oceanic crust; determine how fluid pathways are distributed within an active hydrothermal system; and elucidate relations between fluid circulation, alteration, microbiology, and seismic properties. Goals are being addressed through drilling, coring, shipboard and shorebased analysis of recovered materials, wireline logging, active hydrologic experiments, modeling, and (ongoing) long-term monitoring of conditions within borehole observatories (CORKs) that extend up to ~650 m below the seafloor.
On Expedition 301 we recovered and replaced one CORK that had been installed in 1996, and drilled two new holes and installed new observatories 1 km to the south. In combination with one additional pre-existing CORK, this created a network of monitoring and sampling points arranged in an "L" pattern, with one of the new CORKs isolating multiple depth intervals. We also sampled upper ocean crustal rocks, collected geophysical logs, and performed the longest pumping experiments (as of that time) in the ocean crust. I subsequently served as co-chief scientist IODP Expedition 327 in July–September 2010, with Takeshi Tsuji (Kyoto University), and we installed two additional CORK systems in the same area (Site 1362), expanding the observatory network to six. The newer CORKs include several innovative design elements, including coated and perforated casing and collars (allowing penetration and recovery of instruments from unstable zones, while maintaining geochemically and microbiologically "clean" conditions), swellable packers (along with hydraulic packers) to isolate basement and casing zones, and a lateral pipe coming off the central casing string, topped with a ball valve and ring clamp. The latter is used for running long-term flow and sampling experiments under controlled conditions, as described below. During Expedition 327 we also ran a 24-hour pumping experiment, by far the longest during scientific ocean drilling, and injected a cocktail of seven tracers, with contemporaneous and long-term sampling at other CORK locations.
Here you can see images taken aboard the R/V Atlantis and from the ROV Jason during Summer 2011 observatory servicing operations. The photo on the left shows Jason using a special tool to extract part of an observatory. The central image shows a new manifold being carried to a wellhead for insertion. The right image shows shimmering hydrothermal fluid emerging from a flowmeter on another wellhead, with a fluid sampling tube being moved into position.
Geoff Wheat runs the winch to recover a downhole instrument string in 2008. Amalia Slovacek (undergraduate researcher) shows configuration of a calibration elevator used with the flowmeter shown above, Summer 2011. Image on right shows the ROV Jason being prepared for launch.
 |
 |
 |
I was lead co-PI on another NSF project (with five co-PIs from five institutions) to investigate ridge-flank hydrothermal circulation within 18-24 Ma lithosphere offshore of Costa Rica in the eastern Pacific Ocean. The study area is unusual in that seafloor heat flow over a large region is only 10-30% of that expected for the lithospheric age; in one location, heat flow is 1% of the conductive prediction. There is an abrupt transition between abnormally cool and normal-to-warm seafloor that coincides with a boundary between crust formed at the East Pacific Rise (EPR) and that formed at the Cocos-Nazca Ridge (CNR). This project involved two research expeditions in 2001 and 2002, with seismic, swath-mapping, heat flow measurements, and sediment coring. The first expedition focused on regional features and trends, whereas the second focused on the influence of basement outcrops on hydrothermal circulation. Work during the first expedition demonstrated that the thermal transition between areas of suppressed and elevated heat flow is extremely abrupt and thus must have a shallow, hydrothermal origin. In addition, it appears that basement outcrops (seamouts) also play a critical role in ventilating EPR-generated crust, a process that does not occur on similarly-aged CNR-generated crust of the same age. This observation suggests that there is a fundamental difference in the nature of basement hydrogeology on these two parts of the plate, perhaps with higher and more continuous permeability in fast-spread (EPR) crust. Three UCSC graduate students and two post-doctoral researchers participated on this project (Hutnak, H. Deshon, P. Friedmann, A. Cherkaoui, P.Pizani), as did five UCSC Earth Sciences majors. Seven Earth Sciences majors completed senior thesis on the basis of work associated with this project, the most recent in Spring 2005. One of the most exciting results of this cruise was published in Nature Geoscience in Fall 2008. This paper shows that the flow of warm hydrothermal fluid from outcrops on the cool side of the Cocos Plate extracts as much heat as a black smoker vent field, but at much lower temperatures. Fluid fluxes are thousands of L/s! We are going back to this field site in Fall 2013, to try to find the "firehose" of low-temperature hydrothermal fluid, and to quantify the rates at which fluid, heat, and solutes leave the seafloor.
I was PI on an NSF-funded project, collaborating with H. Villinger (U. Bremen), to develop a new generation of subseafloor temperature measurment tools for use while piston coring from a drilling platform. The new tools take advantage of recent advances in electronics and computing capabilities and will improve on the quality of acquired data and in interpretations based on these measurements. Previous generations of similar tools have included a sensor and logger package installed within the piston core cutting shoe; the new development will also include design and creation of a new top sub that will permit deployment of two instruments during a single tool lowering, allowing determination of a thermal gradient. I am working cooperatively with Villinger and one of his graduate students, M. Hessemann on: electronics design, prototyping, and testing; modeling of tool response; discussion and transfer of documents between vendors, PIs, and the IODP non-riser, science operator; creation of a front-end interface for tool operation, data acquisition, and processing; construction of working tools; design and construction of two sets of mechanical parts (shoes and top subs); hardware and supplies for testing and tool calibration; calibration at a suitable facility; preparation of a “cookbook” to be used by shipboard technicians and scientists for tool operation; and travel to transfer hardware and software and train technicians and scientists on tool operation. These tools have now been delivered to the U.S. Implementing Organization to IODP, and are being use on both the U.S. and Japanese drilling vessels.
Much of the seafloor hydrothermal circulation modeling work my colleagues and I have completed in the last eight years was facilitated through collaboration with colleagues at Los Alamos National Laboratory (LANL), who have developed a computer code (FEHM) and associated programs that we use to simulate coupled heat-fluid-solute transport. We have modified this code to allow it to represent rock compressibility under non-isothermal conditions and calculate fluid properties (density, viscosity, enthalpy) over a wider P-T range than was possible originally. In addition, we have developed >25 pre- and post-processors for preparation of input and interpretation of numerical results. We have ported an updated version of the modified code to a Linux platform, which will allow us to run more and faster simulations, and are exploring options for conditional simulation, representation of geological heterogeneity, and reactive transport.
Join the UCSC Hydrogeology Research Group?
As of Summer 2023 the UCSC Hydrogeology Research Group includes three graduate student researchers for whom A. Fisher is primary advisor (A. Serrano, E. Kam, and K. Dickerson - Fisher is co-supervisor for others), with two new graduate students starting in Summer/Fall 2023 (R. Akiba, E. Yan), and we work with numerous undergraduate student researchers. We collaborate with researchers, staff, and students in the Resource Conservation District - Santa Cruz County UC Merced, UC Davis, UC Berkeley, UCSC Environmental Studies Department, Oregon State University, Los Alamos National Laboratory, University of Bremen, the U.S. Geological Survey, the Pajaro Valley Water Management Agency, University of Miami, University of Hawaii, University of Illinois, Pacific Geoscience Center (Geological Survey of Canada), Monterey Bay Aquarium Research Institite,Texas A & M University, UC Santa Barbara, Scripps Institution of Oceanography, Woods Hole Oceanographic Institution, Lamont Doherty Earth Observatory, and other institutions. Former undergraduate student researchers have been admitted to excellent graduate programs in hydrogeology and related fields and found employment as Earth Science professionals. Former graduate student researchers and postdocs have taken industrial, teaching, not-for-profit, research, and faculty positons throughout the U.S. and overseas.
Do the projects described earlier on this page sound interesting to you? Perhaps you should think about joining the UCSC Hydrogeology Research group. UCSC is a great institution, the Earth and Planetary Sciences Department is among the best in the world, and Santa Cruz is a wonderful place to live, work, and play. Please read the information below pertaining to your educational and professional status and contact me if you would like to contribute to our research program. Note: I am especially keen on enhancing diversity in STEM fields and working with students and post-docs who have overcome hardships in achieving academic excellence. I am committed to making research, teaching, and technical opportunities available to all applicants who demonstrate creativity, skill, and determination.
Current weather in Santa Cruz, CA: SANTA CRUZ WEATHER
Postdoctoral Research Opportunities in Hydrogeology at UCSC
I might consider hiring a postdoc, depends on project development and funding. Work could include either land-based hydrogeology or subseafloor studies. You can tell me if you have an idea and/or are interested in writing a proposal.
MINIMUM QUALIFICATIONS: Ph.D. in hydrogeology, geology, geochemistry, geophysics, engineering or a related field; strong computational skills (including code development/modification and/or visualization); strong labotatory and/or field skills and interests; keen interest in an academic/research career; no more than three years of previous postdoctoral research experience; ability to work independently and as part of a team; strong communication (writing, speaking) and interpersonal skills.
PREFERRED QUALIFICATIONS: Expertise in one or more of the following research areas (and interest in learning others): marine or terrestrial geothermics, surface water - groundwater interactions, numerical modeling of coupled flows (fluid-heat, fluid-solute), biogeochemistry and/oir microbiology, familiarity with GIS, modeling and/or optimization techniques, with reflection seismic, multibeam, and/or borehole geophysical data, cross-hole hydrogeologic (tracer, flow) testing.
There are several posdoctoral fellowship programs that could support this positon, as could research grants. For example, there is the UC Presidential Postdoctoral Fellowship program (deadline in November each year).
Please contact me if a postdoc with the UCSC Hydrogeology group interests you.
Graduate Research Opportunities in Hydrogeology at UCSC
I am NOT currrently recruiting new graduate students for the 2023-24 cycle (beginning work in Summer or Fall 2024).
Undergraduate Research Opportunities in Hydrogeology at UCSC
I have supervised >50 undergraduate student researchers in projects involving field work and lab work, many of whom completed a senior thesis in satisfaction of their UCSC "Capstone Requirement." Depending on how various projects and proposals go this year, I am likely to have one or more additional projects for motivated undergraduates. I prefer that students working with my lab group complete a senior thesis as part of a larger project involving me and my other students and research collaborators. Ideal candidates will have an outstanding record of achievement both within and outside the Earth and Planetary Sciences Department, including quantitative coursework. Successful undergraduate student researchers have strong writing skills, the ability to work effectively both alone and in a group, and committment to their research projects. Prior experience is not necessary. If you wish to be considered, please contact me.
this page last updated: 02-Jul-2023