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The hydrogeology of Yellowstone: It's all about the cold water

Cross posted at Highly Allochthonous

ResearchBlogging.orgThe Yellowstone caldera is home to thousands of geothermal springs and 75% of the world’s geysers, with kilometers-deep groundwater flow systems that tap magmatic heat sources. As that hot groundwater rises toward the surface, it interacts with shallower, cooler groundwater to produce multi-phase mixing, boiling, and a huge array of different hydrothermal features. While the deep, geothermal water is sexy and merits both the tourist and scientific attention given to it, there’s a largely untold story in the shallow groundwater, where huge volumes of cold water may advect more heat than the hydrothermal features.

Grand Prismatic Spring at Yellowstone National Park. Photo by Alaskan Dude on Flickr.
Grand Prismatic Spring. (Photo by Alaskan Dude on Flickr.)

Yellowstone is a rhyolitic caldera that has produced 6000 cubic kilometers of ash flow tuffs, rhyolites, and basalts that form a poorly-characterized, heterogeneous fractured rock aquifer, hosting both hot/deep and cold/shallow flow systems. The Yellowstone volcanics lie on top of the Rocky Mountain Cordillera, which itself is a complex hydrogeologic system, ranging from low permeability metamorphic rocks to high permeability limestones.

In a paper in the Journal of Hydrology, Gardner and colleagues (2010) use stream hydrographs and groundwater residence times to characterize the cold, shallow groundwater of the greater Yellowstone area. Stream hydrographs, or the time series of stream discharge, are useful indicators of groundwater dynamics, because in between rain or snowmelt events, streamwater is outflowing groundwater. The recession behavior of a hydrograph during periods between storms can be used to estimate aquifer volumes. In the Yellowstone region, the annual hydrograph is strongly dominated by the snowmelt peak, and Gardner et al. used the mean daily discharge record from 39 streams to characterize the recession behavior of streams on different lithologies. What they found was that streams flowing in watersheds dominated by volcanic rocks have much less variable hydrographs than those on other rock types. The figure below uses data from the USGS to illustrate these differences, which are in line with studies in the Oregon Cascades* and elsewhere which suggest that young volcanic rocks produce groundwater-fed streams with muted hydrographs.

Daily discharge for the Firehole River (USGS gage #06036905) and Soda Butte Creek (USGS gage #06187950) for the 2006-2007 water years, expressed on a unit area basis.

Using a nifty technique to separate the recessions into components attributable to snowmelt versus groundwater, Gardner et al. were able to calculate a ratio of the groundwater discharge to the total discharge of each stream and to calculate the hydraulic diffusivity, which is a ratio of permeability (how easily a fluid moves through a rock) compared to the amount of water stored in the system. If hydraulic diffusivity is low, the flow in the stream decreases slowly over time, like the Firestone River in the figure above. But hydraulic diffusivity can be low either because of low permeability or large aquifer storage volumes, so being able to tease apart those two components is key to understanding the hydrograph behavior. Gardner et al. did this by looking at the ratio of groundwater discharge to maximum discharge and using that as an index of aquifer storage. Based on these ratios, Gardner et al. separated the streams in the Yellowstone area into three groups (runoff-dominated, intermediate, and groundwater-dominated) with contrasting hydrogeologic properties.

Upper Cenozoic Geologic Map, Yellowstone Plateau
Geologic map of a portion of the Yellowstone Plateau, with approximate locations of stream gages of interest noted. Modified from Christiansen (2001, USGS Prof. Pap. 729-G).

Soda Butte and Teton Creeks are runoff dominated, with low groundwater storage and middling recession behavior. Since there is little groundwater storage, in order for hydraulic diffusivity to be low, then permeability must also be low. Sure enough, Teton Creek lies on top of Precambrian gneiss and granite, and unfractured metamorphic and intrusive igneous rocks like these have the lowest possible permeabilities. The Soda Butte Creek watershed comprises Eocene Absaroka volcanics, and older volcanic rocks like these can be quite weathered to clays and relatively impermeable.

The intermediate watersheds of Tower Creek and Cache Creek have significant ratios of groundwater discharge to maximum discharge, but their hydrographs recede rapidly over the summer. This means that they have high permeabilities relative to their aquifer storage volume. The Tower Creek watershed has Eocene tuffs and glacial valleys with alluvial fill, and Cache Creek watershed has Paleozoic carbonates. These materials are known for their high permeabilities, and the low storage volumes can be explained if those layers thinly overly less conductive materials.

The Firehole River, Gibbon River, and Snake River above Jackson Lake are groundwater-dominated, with very high permeabilities but even larger aquifer storage volumes. All of those streams drain primarily Quaternary Yellowstone volcanics, and this hydrologic behavior is in keeping with other young volcanic terrains.

Not content to stop with this hydrogeologic classification of the Yellowstone area, Gardner et al. collected water samples from small, cold springs to analyze CFC and tritium concentrations, which are useful tracers of groundwater travel times. For the springs they sampled, they found an average travel time (from recharge to discharge) of ~30 years. Using those CFC-derived groundwater transit times and some back-of-the-envelope estimates of aquifer geometry, Gardner et al. estimate that the Quaternary Yellowstone volcanics have a permeability of 10-11 to 10-13 m2, which is in line with estimates of young volcanics elsewhere. They also estimated that the aquifer depth represented by these small springs was ~70 m, but speculated that deeper flowpaths might have been discharging directly into the streams, out of reach of their CFC and tritium sampling abilities.

Finally, Gardner et al. note that the cold springs they studied are actually not as cold as they should be. In fact, they appear to be what are coming to be called “slightly thermal” springs. Groundwater recharge temperature is commonly assumed to be approximately mean annual temperature, and in the Norris Geyser Basin area, that’s around 4-5 &deg C. But the cold springs in the area are around 10 &deg C. Using this temperature difference and a handy equation from Manga and Kirchner (2004), Gardner et al. are able to calculate the heat flux advected by these cool springs. Their value of ~3800 W/m2 for the springs around Norris is about 10% of the heat flux from the Norris and Gibbon Geyser Basins themselves. That number becomes even more astonishing when you consider the relative scales of the cool versus the thermal groundwater systems. Geyser basins cover ~10 km2 of the Yellowstone Plateau, whereas cool groundwater drains under the entire ~1000 km2 plateau, and could be discharging far more heat than those showy thermal springs and geysers themselves.

So if you happen to go to Yellowstone this summer, in between gawking at Old Faithful, Artist Paint Pots, and Mammoth Hot Springs, take a few moments to appreciate the waters of the less dramatic cool rivers and streams. Their waters too are profoundly shaped by the geologic history of Yellowstone, and they are taking an awful lot of heat.

*Disclaimer: My PhD research focused on the hydrology and hydrogeology of volcanic aquifers and streams of the Oregon Cascades.

Payton Gardner, W., Susong, D., Kip Solomon, D., & Heasler, H. (2010). Snowmelt hydrograph interpretation: Revealing watershed scale hydrologic characteristics of the Yellowstone volcanic plateau Journal of Hydrology, 383 (3-4), 209-222 DOI: 10.1016/j.jhydrol.2009.12.037

Is Anne a hydrologist? geomorphologist? hydrophillic geologist? or whathaveyou?

Cross-posted at Highly Allochthonous

The theme for the next edition of the geoblogosphere’s Accretionary Wedge carnival is along the lines of “what are you doing now?” Recently as I was whining to my Highly Allochthonous co-blogger about how busy my teaching was keeping me, and how I wouldn’t have time to write anything for the Wedge, Chris suggested that I exhume some navel-gazing writing I’d done a while ago and simply post that. And in slightly modified form, now I have.

So, what do I do? The major theme of my research is analyzing how geologic, topographic, and land use variability controls hydrologic response, climate sensitivity, and geomorphic evolution of watersheds, by partitioning water between surface and ground water. The goal of my research is to improve reach- to landscape-scale prediction of hydrologic and geomorphic response to human activities and climate change. My work includes contributions from field studies, stable isotope analyses, time series analyses, geographic information systems, and hydrological modeling. My process-based research projects allow me to investigate complex interactions between hydrology, geomorphology, geology, and biology that occur on real landscapes, to test conceptual models about catchment functioning, and to show whether predictive models are getting the right answers for the right reasons. My current and past research has allowed me to investigate landscapes as diverse as the Cascades Range volcanic arc, the Appalachian Mountains and Piedmont of the southeastern United States, the Canadian Arctic Archipelago, and the Upper Mississippi River watershed.

My on-going and developing research program focuses on three areas:

  1. Watershed influences on hydrologic response to climate variability and change;
  2. Controls on and effects of partitioning flowpaths between surface water and groundwater; and
  3. Influence of hydrologic regimes on landscape evolution and fluvial geomorphology

If you really want the long version of my research interests, venture onward. But don’t say I didn’t warn you.

Watershed influences on hydrologic response to climate variability and change

On-going climate change is predicted to have dramatic effects on the spatial distribution and timing of water resource availability. I use historical datasets, hydrologic modeling, and GIS analysis to examine how watershed characteristics can mediate hydrologic sensitivity to climate variability and change. Currently, I focus on climate sensitivity in watersheds with seasonal and transient snow and on down-scaling hydrologic impacts of climate change to smaller watersheds.

Watersheds with seasonal and transient snow: A long-held mantra is that watersheds with extensive groundwater are buffered from climate change effects, but in a pair of papers set in the Oregon Cascades, my collaborators and I showed the opposite to be true. Minimum streamflows in watersheds with abundant groundwater are more sensitive to loss of winter snowpack than in watersheds with little groundwater (Jefferson et al., 2008, Tague et al., 2008). Glaciers are another water reservoir often thought to buffer climate change impacts, and in a paper in review, we show that projected glacier loss from Mt. Hood will have significant impacts on water resources in the agricultural region downstream.

I have also been examining hydroclimate trends relative to hypsometry (elevation distribution) of watersheds in the maritime Pacific Northwest. Almost all work investigating hydrologic effects of climate change in the mountainous western United States focuses on areas with seasonal snowpacks, but in the maritime Northwest, most watersheds receive a mixture of winter rain and snow. My research investigates how much high-elevation watershed area is necessary for historical climate warming to be statistically detectable in streamflow records. Preliminary results were presented at the American Geophysical Union meeting in 2008, and I’m working on a paper with more complete results. Extending this work into the modeling domain, I am currently advising a graduate student using SnowModel to investigate the sensitivity of snowmelt production to projected warming in the Oregon Cascades, Colorado’s Fraser Experimental Forest, and Alaska’s North Slope, in collaboration with Glen Liston (Colorado State University).

Down-scaling climate impacts to watersheds and headwater streams: Most studies of hydrologic impacts of climate change have focused on regional scale projections or large watersheds. Relatively little work has been done to understand how hydrologic and geomorphic impacts will be felt in mesoscale catchments or headwater stream systems, yet most of the channel network (and aquatic habitat) exists in these small streams. In August 2009, I submitted a proposal to a Department of Energy early career program to investigate the effect of climate change on hydrology of the eastern seaboard of the US. This work proposed to contrast North Carolina’s South Fork Catawba River and New Hampshire’s Pemigewassett River and their headwater tributaries through a combination of modeling and field observations of the sensitivity of headwater stream networks to hydroclimatic variability. While the project was not funded, I am using the reviews to strengthen the proposal, and I plan to submit a revised proposal to NSF’s CAREER program in July. I have a graduate student already working on calibrating the RHESSys hydroecological model for the South Fork of the Catawba River.

Controls on flowpath partitioning between surface water and groundwater and the effects on stream hydrology, geomorphology and water quality

Many watershed models used in research and management applications make simplifying assumptions that partition water based on soil type and homogeneous porous bedrock. These assumptions are not reflective of reality in many parts of the world, including the fractured rocks of North Carolina’s Piedmont and Blue Ridge provinces. I am interested in understanding how water is partitioned between groundwater and surface water in heterogeneous environments, and what effect this partitioning has on stream hydrology, geomorphology, and water quality. My interest in the controls on flowpath partitioning began during my work in the Oregon Cascades Range, where I showed that lava flow geometry controlled groundwater flowpaths and the expression of springs (Jefferson et al., 2006). Currently, I am using fractured rock environments and urbanizing areas as places to explore the effects of heterogeneous permeability.

Fractured rock: The Piedmont and Blue Ridge provinces of the eastern United States are underlain by crystalline rocks, where groundwater is largely limited to discrete fractures. Groundwater-surface water interactions on fractured bedrock are largely unexplored, particularly at the scale of small headwater streams. I am interested in how groundwater upwelling from bedrock fractures and hyporheic flow influence the hydrology and water quality of headwater streams. A small grant facilitated data collection in three headwater streams which is forming the thesis for one of my graduate students, has precipitated a collaborative project with hydrogeologists from the North Carolina Division of Water Quality, and will serve as preliminary data for a proposal to NSF Hydrologic Sciences in June 2010.

Urban watersheds: Urbanization alters the partitioning of flowpaths between surface water and groundwater, by creating impervious surfaces that block recharge and installing leaky water and sewer lines that import water from beyond watershed boundaries. Also, the nature of the drainage network is transformed by the addition of stormwater sewers and detention basins. In September 2009, my collaborators and I submitted a proposal to NSF Environmental Engineering to look at how stormwater best management practices (BMPs) mitigate the effects of urbanization on headwater stream ecosystem services. While we weren’t funded, we were strongly encouraged to resubmit and did so in March 2010. We are also submitting a proposal to the National Center for Earth Surface Dynamics (NCED) visitor program to use the Outdoor Stream Lab at the University of Minnesota to investigate the interplay between stormwater releases and in-stream structures.

Influence of hydrologic regimes on landscape evolution and fluvial geomorphology

The movement of water on and through the landscape results in weathering, erosion, transport, and deposition of sediment. In turn, that sediment constrains the future routing of water. I am interested in how the hydrologic regime of a watershed affects the evolution of topography and fluvial geomorphology. My work in this area has examined million-year scales of landscape evolution in high permeability terrains, century-scale evolution of regulated rivers, and the form and function of headwater channels.

Evolution of high permeability terrains: The youngest portions of Oregon’s High Cascades have almost no surface water, because all water infiltrates into high permeability lava flows. Yet on older parts of the landscape, streams are abundant and have effectively eroded through the volcanic topography. In a paper in Earth Surface Processes and Landforms (Jefferson et al., 2010), I showed that this landscape evolution was accompanied and facilitated by a hydrologic evolution from geomorphically-ineffective stable, groundwater-fed hydrographs to flashy, runoff-dominated hydrographs. This coevolutionary sequence suggests that permeability may be an important control on the geomorphic character of a watershed.

Human and hydrologic influences on large river channels: Almost all large rivers in the developed world are profoundly affected by dams, which can alter the hydrologic regime by suppressing floods, supplementing low flows, and raising water levels in reservoirs. On the Upper Mississippi River, in the 70 years since dam construction, some parts of the river have lost islands, and with them habitat diversity, while in other areas new islands are emerging. In 2008-2009, I had a small grant that facilitated the examination of some islands with a unique, unpublished long-term topography dataset and its correlation with hydrologic patterns and human activities. This project became the thesis research of one of my graduate students, who will be defending his M.S. in May 2010.

Headwater channel form and function: Although headwater streams constitute 50-70% of stream length, the geomorphic processes that control their form and function are poorly understood. Most recent research on geomorphology of headwater streams has focused on streams in very steep landscapes, where debris flows and other mass wasting processes can have significant effects on channel geometry. In the Carolina Piedmont, gentle relief allows me to investigate the formation and function headwater channel networks, isolated from mass wasting processes. One of my graduate students has collected an extensive sediment size distribution dataset which shows that, at watershed areas <3 km2, downstream coarsening of sediment is more prevalent than the downstream fining widely observed in larger channels. Another graduate student is collecting data on channel head locations and flow recurrence and sediment transport in ephemeral channels in order to sort out the relative influences of topography, geology, and legacy land use effects on the uppermost reaches of headwater streams. Both of these projects have already resulted in presentations at GSA meetings.

Whew. So that’s what I do, between teaching some field-intensive courses and raising a preschooler. But, what am I? Hydrologist? Geomorphologist? Hydrophillic geologist? Or something else entirely?

My picks of the December literature

Cross-posted at Highly Allochthonous

I’m a few days behind on sharing my picks from December’s journals, but Chris has been doing such a stupendous job of sharing absolutely wonderful geology posts (and of deconstructing terrible science reporting), that I hardly feel guilty waiting until he’s occupied with travels before sneaking this post onto the blog.

Without further ado, here is the odd assortment of articles that hit my email box in December that I found most intriguing. They reflect a mixture of my past, present, and future research and teaching interests and should not be considered a reflection of anyone else’s tastes in science.

Burbey, T.J. (2010) Fracture characterization using Earth tide analysis, Journal of Hydrology, 380:237-246. doi:10.1016/j.jhydrol.2009.10.037

Tides are popping up all over in the geology literature these days, from the Slumgullion earthflow (atmospheric tides) to the San Andreas fault (earth tides). Here Burbey uses water-level fluctuations in fractured rock confined aquifers to quantify specific storage and secondary porosity. Fractured rock aquifers are notoriously tricky to understand, and this method gives hydrogeologists one more tool in their arsenal for understanding places like the Blue Ridge Mountains and the Piedmont. Since I’m getting interested in the fractured rocks in just those areas, this paper caught my eye.

Burnett, W.C., Peterson, R.N., Santos, I.R., and Hicks, R.W. (2010) Use of automated radon measurements for rapid assessment of groundwater flow into Florida streams Journal of Hydrology, 380:298-304. doi:10.1016/j.jhydrol.2009.11.005

Radon is a conservative tracer with concentrations several orders of magnitude higher in groundwater than surface water. That means that it can be used to evaluate the groundwater inputs into different stream reaches, though it is often used in conjunction with other tracers to get quantitative estimates. In this paper, Burnett and colleagues lay out a method for using radon as a sole tracer to quantify groundwater discharge. I’m looking around for tracers to separate overland flow, flow through the soil/saprolite, and groundwater from rock fractures, so this paper piqued my interest as radon is one candidate I’m learning more about.

Garcia-Castellanos, D., Estrada, F., Jiménez-Munt, I., Gorini, C., Fernàndez, M., Vergés, J. and De Vicente, R. 2009. Catastrophic flood of the Mediterranean after the Messinian salinity crisis. Nature, 462, 778-781, doi:10.1038/nature08555.

5.6 million years ago the Mediterranean basin was nearly dry and highly saline in the midst of a period known as the Messinian salinity crisis, but 5.33 million years the Atlantic Ocean rapidly refilled the basin by overtopping and incising through the sill at the Straits of Gibraltar. How fast did that sea refill? How big was the peak discharge? And what did all that water do the straits itself? Those are the questions tackled in this paper, which combines borehole and seismic data with hydrodynamic and morphodynamic modeling. The story that Garcia-Castellanos and colleagues tell as a result of their work is truly astounding. The Atlantic Ocean overtopped the sill and slowly began to refill the Mediterranean, but as the sill eroded, discharge (and incision) increased exponentially until peak discharges on the order of 108m3/sec were reached and sea levels in the Mediterranean were increasing by up to 10 m per day.  While the beginning and the end of the flood may have stretched out for thousands of years, the modeling work suggests that the vast majority of water transfer and the incision of greater than 250 m deep canyons across the Straits of Gibraltar was done on a time scale of several months to two years. That peak discharge is ten times greater than that estimated for the Missoula Floods, themselves not trifling events, and there may have been profound paleoclimate repercussions from such a significant change in the region’s hydrological status.

Grimm, R. E., and S. L. Painter (2009), On the secular evolution of groundwater on Mars, Geophys. Res. Lett., 36, L24803, doi:10.1029/2009GL041018.

Grimm and Painter created a 2D pole-to-equator model of subsurface water and carbon dioxide transport, initiated the model by simulating sudden freezing, and then looked at the effects over geologic time scales (secular evolution). According to their abstract, their model predicts water to be found in different places on the Martian landscape than previous ideas had suggested. I guess we’ll just have to go look and see who is right.

Jiang, Xiao-Wei; Wan, Li; Wang, Xu-Sheng; Ge, Shemin; Liu, Jie Effect of exponential decay in hydraulic conductivity with depth on regional groundwater flow Geophys. Res. Lett., 36, L24402, doi:10.1029/2009GL041251.

In soils and in the Earth’s crust, hydraulic conductivity (K) generally decreases exponentially with depth. This phenomenon is the result of the compaction and compression of the overlying strata. In this paper, Jiang and colleagues examine the implications such decreases in K on local versus regional groundwater flow systems. They find that the more quickly K decreases, the less water makes into the deeper regional flow systems and local flow systems extend deeper into the subsurface. They suggest that when hydrogeologists try to interpret regional flow problems, that we need to bear in mind the effects of decreasing K on the systems.

Knight, D.B. and Davis, R.E. 2009. Contribution of tropical cyclones to extreme rainfall events in the southeastern United States. J. Geophys. Res., 114, D23102, doi:10.1029/2009JD012511.

Knight and Davis used 25 years of observational, wind-corrected, and reanalysis data for the southeastern Atlantic coastal US states and found that extreme precipitation from tropical storms and hurricanes (TCs) has increased over the study period.  They find that this increase in TC contribution to extreme precipitation is a function of increasing storm wetness and frequency, but not storm duration. If TCs are producing more precipitation, their flood hazards are also increasing, and flooding is already the leading cause of deaths associated with TCs.

Meade, R.H. and Moody, J.A. 2009. Causes for the decline of suspended-sediment discharge in the Mississippi River system, 1940-2007. Hydrological Processes. 24, 35-49. doi:10.1002/hyp.7477

Dams on the Missouri and Upper Mississippi Rivers have been blamed for trapping almost 2/3 of the sediment that used to reach the Lower Mississippi and Delta.  Here, Meade and Moody show that the dams are only trapping half of the missing sediment, while engineering practices such as bank revetments and meander cutoffs, combined with better erosion control practices in the drainage basin, probably account for the rest. Meade and Moody suggest that this river system, in the largest basin in North America, has been transformed from transport-limited to supply-limited, which is a pretty amazing fundamental shift in the behavior of the river and its ability to deliver sediments to the Gulf of Mexico. [Note that there’s another article in the same issue on “A quarter century of declining suspended sediment fluxes in the Mississippi River and the effect of the 1993 flood.” Both articles are in the public domain and not subject to US copyright laws, though there doesn’t seem to be an obvious way to take advantage of that from the Wiley website.]

Neumann, R.B.,  Ashfaque, A.N,  Badruzzaman, A. B. M.,  Ali, M.A.,  Shoemaker, J.K., and Harvey, C.F. 2010. Anthropogenic influences on groundwater arsenic concentrations in Bangladesh, Nature Geoscience 3, 46-52. doi:10.1038/ngeo685

The story of groundwater of southeast Asia’s deltas, where tens of millions of people live at risk of arsenic poisoning from their drinking water, is perhaps the most compelling contemporary scientific story of how geology, geomorphology, hydrology, and humans intertwine. It’s also an extremely complicated story, with arsenic-laden sediment from the Himalayas settling in the deltas , irrigated rice fields and ponds  changing the local groundwater flow patterns, and microbially mediated oxidation of organic carbon driving the geochemical release of the arsenic into the groundwater. This story has been being pieced together in many papers in the last several years, and in this paper Neumann et al. show that groundwater recharge from the ponds, but not the rice fields, draws the organic carbon into the shallow aquifer, and then groundwater flow modified by pumping brings the carbon to the depths with the greatest dissolved arsenic concentrations. Add some biogeochemistry data, isotope tracing of source waters, incubation experiments, and 3-D flow modeling, and this paper adds some important elements to our understanding of how this public health risk came to be – and how we might be able to mitigate the risks for the people who have little choice but to drink the water from their local wells. [Also note that the same issue of Nature Geosciences has another article on “arsenic relase from paddy soils during monsoon flooding” as well as an editorial, commentary, backstory, and news and views piece on the southeast Asia arsenic problem.]

Pritchard, D., G. G. Roberts, N. J. White, and C. N. Richardson (2009), Uplift histories from river profiles, Geophys. Res. Lett., 36, L24301, doi:10.1029/2009GL040928.

In rivers that have adjusted to their tectonic and climatic regimes, the long profile of a river is smooth and concave. The interesting places are where river profiles don’t look like that ideal. This paper interprets river longitudinal profiles as a way to understand the tectonic uplift history of the area, through a non-linear equation. They check their interpretation against an independently constrained uplift history for a river in Angola.

Stone, R. 2009. Peril in the Pamirs. Science 326(5960): 1614-1617. doi: 10.1126/science.326.5960.1614

Dave Petley at Dave’s Landslide Blog has the must-read summary of this article on the risks associated with the giant lake impounded by the world’s tallest landslide dam. This is seriously fascinating stuff. I already talked a bit about the Usoi Dam in my dam-break floods spiel in my Fluvial Processes class, and now I have more ammunition for this year’s crop of students. In the same issue of Science, Stone also summarizes some of the other water issues facing Central Asia.

Please note that I can’t read the full article of AGU publications (including WRR, JGR, and GRL) until July 2010 or the print issue arrives in my institution’s library. Summaries of those articles are based on the abstract only. UNC Charlotte also does not have access to Nature Geoscience.

My picks of the November literature

It is not that there was no October literature to pick. My time to read articles simply disappeared in the lead-up to and excitement of the Geological Society of America meeting. This month, however, I am back on track and I will try to update this post as I move through the last few weeks of November.

Fussel, H-M. 2009. An updated assessment of the risks from climate change based on research published since the IPCC Fourth Assessment Report. Climatic Change (2009) 97:469–482. doi:10.1007/s10584-009-9648-5
The takeaway message is this: While some topics are still under debate (e.g., changes to tropical cyclones), most recent research indicates that things are looking even worse now than we thought a few years ago. Greenhouse gas emissions are rising faster than we anticipated, and we have already committed to substantial warming, which is currently somewhat masked by high aerosol concentrations. It is increasingly urgent to find mitigation and adaptation strategies. Not good.

Gardner, LR. 2009. Assessing the effect of climate change on mean annual runoff. Journal of Hydrology. 379 (3-4): 351-359. doi:10.1016/j.jhydrol.2009.10.021
This fascinating article starts by showing a strong correlation (r2 = 0.94) between mean annual runoff and a function of potential evapotranspiration and precipitation. The author then goes on to derive an equation that shows how temperature increases can be used to calculate the change in evapotranspiration, therefore solving the water budget and allowing the calculation of the change in mean annual runoff. Conversely, the same equation can be used to solve for the necessary increase in precipitation to sustain current runoff under different warming scenarios.

Schuler, T. V., and U. H. Fischer. 2009.Modeling the diurnal variation of tracer transit velocity through a subglacial channel, J. Geophys. Res., 114, F04017, doi:10.1029/2008JF001238.
The authors made multiple dye tracer injections into a glacial moulin and then measured discharge and tracer breakthrough at the proglacial channel. They found strong hysteresis in the relationship between tracer velocity and proglacial discharge and attributed this hysteresis to the adjustment of the size of a subglacial Röthlisberger channel to hydraulic conditions that change over the course of the day. Cool!

Bense, V. F., G. Ferguson, and H. Kooi (2009), Evolution of shallow groundwater flow systems in areas of degrading permafrost, Geophys. Res. Lett., 36, L22401, doi:10.1029/2009GL039225.
Warming temperatures in the Arctic and sub-arctic are lowering the permafrost table and activating shallow groundwater systems, causing increasing baseflow discharge of Arctic rivers. This paper shows how the groundwater flow conditions adjust to lowering permafrost over decades to centuries and suggests that even if air temperatures are stabilized, baseflow discharge will continue to increase for a long time.

Soulsby, Tetzlaff, and Hrachowitz. Tracers and transit times: Windows for viewing catchment scale storage. Hydrological Processes. 23(24): 3503 – 3507. doi: 10.1002/hyp.7501
In this installment of Hydrological Processes series of excellent invited commentaries, Soulsby and colleagues remind readers that although flux measurements have been the major focus of hydrologic science for decades, it is storage that is most relevant for applied water resources problems. They show that tracer-derived estimates of mean transit time combined with streamflow measurements can be used to calculate the amount of water stored in the watershed. They use their long-term study watersheds in the Scottish Highlands to illustrate how transit time and storage scale together and correlate with climate, physiography, and soils in the watersheds. Finally, they argue that while such tracer-derived storage estimates have uncertainties and are not a panacea, they do show promise across a range of scales and geographies.

Chatanantavet, P., and G. Parker (2009), Physically based modeling of bedrock incision by abrasion, plucking, and macroabrasion, J. Geophys. Res., 114, F04018, doi:10.1029/2008JF001044.
Over the past 2 decades, geomorphologists have developed much better insight into the landscape evolution of mountainous areas by developing computerized landscape evolution models. A key component of such models is the stream power rule for bedrock incision, but some have complained that is not physically based enough to describe. In this paper, the authors lay out a new model for bedrock incision based on the mechanisms of abrasion, plucking, and macroabrasion (fracturing and removal of rock by the impact of moving sediment) and incorporating the hydrology and hydraulics of mountain rivers. This could be an influential paper.

Payn, R. A., M. N. Gooseff, B. L. McGlynn, K. E. Bencala, and S. M. Wondzell (2009), Channel water balance and exchange with subsurface flow along a mountain headwater stream in Montana, United States, Water Resour. Res., 45, W11427, doi:10.1029/2008WR007644.

Tracer tests were conducted along 13 continuous reaches of a mountain stream to quantify gross change in discharge versus net loss and net gain. Interestingly, the change in discharge over some reaches did not correspond to calculations of net loss or net gain based on tracer recovery. These results suggests that commonly used methods for estimating exchange with subsurface flow may not be representing all fluxes. Bidirectional exchange with the subsurface, like that found in this paper, is likely to be very important for nutrient processing and benthic ecology.

Please note that I can’t read the full article of AGU publications (including WRR, JGR, and GRL) until July 2010 or the print issue arrives in my institution’s library. Summaries of those articles are based on the abstract only.

The Hydrology and Evolution of Basaltic Landscapes: Notes from GSA Sunday

This post is cross-posted at Highly Allochthonous. Please look over there for any comments.

Like many North American geobloggers, I’ve recently returned from the Geological Society of America meeting in Portland, Oregon. It was a bittersweet trip for me, as it was a return to my spiritual homeland, where I spent five happy years working on the rocks and waters of the Cascade Range. Since then, I’ve felt a bit exiled on the Eastern Seaboard, so it was perhaps apropos that the trip back was a bit of a tease…in my four days in Oregon, I did not manage to see a single mountain. The picture to the right is the Hood River, draining the north side of Mt. Hood, about 45 minutes east of Portland. It was taken in April 2007, during field work for my post-doc.


After an unexpectedly long layover in Phoenix and an entirely unexpected layover in San Francisco (thank you, US Airways), I arrived in Portland at 1 am local time Sunday morning. With any potential time-change/jet-lag problems thus mitigated, I arrived bright eyed for the first talks on Sunday morning.

The main order of business on Sunday morning was the Pardee Keynote Symposium on “The Evolution of Basaltic Landscapes: Time and River and the Lava Flowing.” I arrived in time to hear a fascinating talk on “Impacts of basaltic volcanism on incised fluvial systems: does the river give a dam?” by blogger/tweep/mapper extraordinaire Kyle House. He was talking about the lava dams, debris flows, and river incision of the Owyhee River of eastern Oregon. After a few gorgeous photos accompanied magnificent Lidar images, I was thoroughly convinced of the utility of Lidar for high-resolution geological mapping. I was also salivating at the thought of a whole day of water + lava talks full of gorgeous volcano photos.

After Steve Ingebritsen gave a lovely overview of the hydrogeology of basalts, Dennis Geist convinced me that I absolutely have to go to the Galapagos Islands, by showing pictures of volcanoes with whales for scale. His talk focused on the connections between geology and biology in the Galapagos, and got me thinking about the implications of volcanic emergence and subsidence for the evolution of the creatures of the famous archipelago. While Geist tried to convince his audience that the vegetation of the Galapagos is supported with basically no soil, neither I nor the next speaker, Oliver Chadwick, quite believed him on that point.

Indeed Chadwick talked about the patterns and processes of soil development on basaltic landscapes, where weathering rates depend not only on the usual climatic factors but also on the flow texture – with aa and pahoehoe flows exhibitting different patterns and timescales of soil development. For my own work, one key point that Chadwick made was “At some point in the history of lava flows, the surface becomes less permeable than the whole…” I think that statement has implications for the way we think about drainage development in basaltic landscapes, but I’ll wait to say more about that until my publication and/or funding record bear me out.

I spent my afternoon thinking more about basalt hydrology, in a session on “Hydrologic Characterization and Simulation of Neogene Volcanic Terranes.” I’ve got lots of notes from that session that are probably of interest only to me, but I will say that it was exciting to hear one of the grad student speakers say to me “I’ve been reading your dissertation” and to hear my work cited more than once. It is such a relief to know that people working in the field actually find my work interesting or useful. Towards the end of the session, I gave a talk on the geomorphic and hydrologic co-evolution of the central Oregon Cascades Range. My talk was based on a paper that has undergone several major revisions since my Ph.D. days, and it was a pleasure to share the latest and greatest incarnation of my thinking on the subject. The pleasure was immeasurably increased by a recent letter from the journal editor giving me only very minor revisions to do before acceptance.

On Sunday evening, the attendees of the morning talks reconvened for a wine tasting with a geological theme – the terroir of taste of Oregon wines grown on basalt versus sandstone. The wine was donated by Willamette Valley Vineyards (basalt) and King Estate (sandstone), and we got to hear from the wine makers as we sipped their wares. According to them, if you see a 2008 Willamette Valley appellation Pinot Noir or Pinot Gris, snap it up. They reckon it will be the best year ever for Oregon wines. That’s saying quite a bit, since Oregon is consistently recognized as one of the world’s best Pinot producing regions.

After a day of stimulating talks and invigorating conversation, I was ready to dive into two days focused on groundwater-surface water interactions and a day of snow, mega-floods, and debris flows to round out my conference. But my notes on those days will have to wait for now, as those paper revisions are not taking care of themselves.

GSA Abstract: On a template set by basalt flows, hydrology and erosional topography coevolve in the Oregon Cascade Range

The Watershed Hydrogeology Lab is going to be busy at this year’s Geological Society of America annual meeting in Portland, Oregon in October. We’ve submitted four abstracts for the meeting, I am co-convening a session, and I’ll be helping lead a pre-meeting field trip.

I’ll be an invited speaker in a session on “Hydrologic Characterization and Simulation of Neogene Volcanic Terranes (T27)” and here’s my abstract:

On a template set by basalt flows, hydrology and erosional topography coevolve in the Oregon Cascade Range

Anne Jefferson

Young basalt terrains offer an exceptional opportunity to understand landscape and hydrologic evolution over time, since the age of landscape construction can be determined by dating lava flows. I use a chronosequence of watersheds in the Oregon Cascade Range to examine how topography and hydrology change over time in basalt landscapes. Western slopes of the Oregon Cascade Range are formed from lava flows ranging from Holocene to Eocene in age, with watersheds of all ages have similar climate, vegetation and relief. Abundant precipitation (2.0 to 3.5 m/yr) falls on this landscape, and young basalts are highly permeable, so Holocene and late Pleistocene lavas host large groundwater systems. Groundwater flowpaths dictated by lava geometry transmit most recharge to large springs. Spring hydrographs have low peak flows and slow recessions during dry summers, and springs and groundwater-fed streams show little evidence of geomorphically effective incision. In the Cascades, drainage density increases linearly with time, accompanied by progressive hillslope steepening and valley incision. In watersheds >1 Ma, springs are absent and well-developed drainage networks fed by shallow subsurface flow produce flashy hydrographs with rapid summer recessions. A combination of mechanical, chemical, and biological processes acting within and on top of lava flows may reduce permeability over time, forcing flowpaths closer to the land surface. These shallow flowpaths produce flashy hydrographs with peakflows capable of sediment transport and landscape dissection. From these observations, I infer that the geomorphic evolution of basalt landscapes is dependent on their evolution from deep to shallow flowpaths.

GSA Abstract: Groundwater contributions to headwater streams on fractured rock in the North Carolina Piedmont and Blue Ridge

The Watershed Hydrogeology Lab is going to be busy at this year’s Geological Society of America annual meeting in Portland, Oregon in October. We’ve submitted four abstracts for the meeting, I am co-convening a session, and I’ll be helping lead a pre-meeting field trip.

The abstract below pulls together some of the work that Cameron More and I have been doing at Redlair, along with similar work by the NC Division of Water Quality at the Allison Woods and Bent Creek research sites. I’m quite hopeful that the work summarized here will be expanded by Cameron for his MS thesis.

Groundwater contributions to headwater streams on fractured rock in the North Carolina Piedmont and Blue Ridge

Anne Jefferson, Department of Geography and Earth Sciences, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223
Joju Abraham, North Carolina Division of Water Quality, Aquifer Protection Section, 610 E Center Ave, Mooresville, NC 28115
Ted Campbell, North Carolina Division of Water Quality, 2090 Highway 70, Swannanoa, NC 28778
Cameron Moore, Department of Geography and Earth Sciences, University of North Carolina at Charlotte, 9201 University City Boulevard, Charlotte, NC 28223

Baseflow is generally assumed to homogenously accrete into headwater channels through flow from soil and porous bedrock, but on crystalline rocks there may be discrete up-welling and down-welling zones associated with fractures. Despite the prevalence of fractured crystalline rocks in the Appalachians and Piedmont of the eastern United States, little work has been done to document and understand groundwater-stream interactions in fractured rock environments.

At three sites in the North Carolina Piedmont and Blue Ridge provinces, groundwater and first-order streams were monitored for temporal and longitudinal temperature and water quality patterns. Stream temperatures at all sites have strong diurnal and seasonal fluctuations, while streambed sediments show smaller diurnal variability. Near-stream piezometers and wells show no diurnal temperature fluctuations, and seasonal fluctuations lag air temperature changes by 1-7 months or are absent. These lags generally increase with depth. In response to rainfall events, a shallow well in a discharge zone at one site (Bent Creek) showed temperature perturbations within 18-20 hours, suggesting upwelling from deeper flow zones. At another site (Allison Woods), rainfall perturbed groundwater temperatures in piezometers screened 1-2.4 m below land surface, but not in wells screened 2.1-7 m below land surface, suggesting groundwater recharge. There is a general trend towards downstream heating in the summer, but several temperature probes deviate from this trend, and synoptic surveys show that some areas with depressed temperatures have elevated specific conductance. These results suggest that there are distinct groundwater upwelling areas within the streambed. At one site (Deep Creek), seasonal variation in stream water isotopes suggest that baseflow is sourced in water <5 years old.

Some streams also have ephemeral reaches that correspond with debris jams and sediment wedges, where all baseflow infiltrates into the stream bed. In other reaches, the streams flow on bedrock with fine alluvium banks and hyporheic exchange may be quite limited. Ongoing work aims to understand the relative importance of hyporheic exchange versus fracture systems in setting the patterns of groundwater-surface water interactions in Piedmont and Blue Ridge headwater streams.

Hydrogeology class in the field

Hydrogeology students discuss their field notes

Hydrogeology students discuss their measurements

In our small but enthusiastic hydrogeology class, we’ve installed piezometers, measured groundwater levels and calculated flow directions, and conducted slug tests in a monitoring well hidden away in a wooded area on campus. We also had a field trip to the Langtree Peninsula Research Station, where hydrogeologists Andrew Pitner and Joju Abraham explained some of their ongoing projects and demonstrated water quality sampling techniques.

Our Langtree field trip took place on the coldest day of the year. Here students warm up by the generator while we wait for water quality indicators to stabilize.

Our Langtree field trip took place on the coldest day of the year. Here students warm up by the generator while we wait for water quality indicators to stabilize.

Cascades hydrogeology on front page of the Oregonian

The front page feature of today’s Oregonian (Portland’s major newspaper) features research on groundwater in the Cascades: The secret’s out: Tons of water in Oregon’s Cascades.

Scientists from the U.S. Forest Service and Oregon State University have in recent years quietly realized that the high Cascades in Oregon and far Northern California contain an immense subterranean reservoir about as large as the biggest man-made reservoirs in the country.

The secret stockpile stores close to seven years’ worth of Oregon rain and snow and is likely to become increasingly precious, even priceless, as population and climate add pressure to water supplies.

The reservoir hides within young volcanic rock — less than 1 million years old — in the highest reaches of the Cascades. The rock is so full of cracks and fissures it forms a kind of vast geological sponge. Heavy rain and snow falling on the rock percolate into the sponge, like a river filling a reservoir.

“It’s not just the fact we get a lot of rain in Oregon that gives us copious amounts of water,” says Gordon Grant, a research hydrologist at the U.S. Forest Service’s Pacific Northwest Research Station leading the research. “It’s the unique geology — the plumbing system — that allows us to retain much of it.”

Much of the work summarized in the article was associated with my Ph.D. research. For some of the details, you can read here and here. For a more complete list of related publications, see here.

Why hydrogeology is so cool

Cross-posted at Highly Allochthonous. Any further discussion will be found there.

Close your eyes. (OK, maybe keep them open so you can read the rest of this post.) Imagine a geosciences specialty where there are lots of jobs right now. Now imagine a specialty where there are lots of jobs year after year after year. In fact, imagine a specialty where, according to the American Geological Institute, there are four jobs for every qualified graduate and it is described as “recession-proof.”

What specialty did you imagine? If you answered “hydrogeology” you’ve either studied the job market or you’ve read a feature in the 8 August issue of Science.

Almost 80% of U.S. hydrogeologists (~18,000 people) work for environmental consulting firms. These companies specialize in helping other companies, communities, and landowners, with issues ranging from water supply exploration and development, source water assessment plans, remediation of contaminated soils and water, and dealing with all sorts of regulations and permitting. Other hydrogeologists work for government agencies and in the mining and petroleum industries. Most of those jobs only require a M.S. degree, but if you decide to go on for a Ph.D., academic jobs are relatively plentiful (at least compared to fields like igneous petrology or, erm, paleomagnetism).

Aside from the good job prospects, what makes hydrogeology a hot field for a student deciding where to specialize? Hydrogeology is perfect for someone interested using their science skills to make a difference in the real world. Everyone needs water to maintain basic bodily functions and sanitation, so most hydrogeology problems can’t help but be “applied research” at some level. Hydrogeology has also got a mix of geology, hydrology, chemistry, and math, so you can never get bored with it. Trying to put aside my own particular research interests, here’s a short list of topics that I’d say are some of the interesting problems in hydrogeology right now.

With increasing population and increasing urbanization, accessing sufficient clean water supplies is a global problem. Surface water supplies, such as rivers and lakes, are often fully allocated and consumed and are more easily contaminated than groundwater. That makes urban groundwater development an attractive option, but because groundwater pumping can affect lake levels and river flows (and vice versa) conjunctive use must be carefully planned and managed. Sounds like a job for a hydrogeologist!

Along the same lines, there’s a lot of interest right now in actively managing the linkages between surface water and groundwater as a way of mitigating climate variations. During wet periods, surface water resources are used and groundwater is artificially recharged, and during dry periods, the groundwater is pumped back out and used. This sort of scheme, called aquifer storage and recovery, is not just of interest in the arid western US, but also in wet places like Florida.

Discovery and clean-up of groundwater contaminated by hazardous wastes, radioactive materials, and sewage effluents are the bread and butter of many hydrogeologists. These problems are not going to go away, but other substances are getting the buzz in the contaminant hydrogeology community. Recent research as documented the widespread occurrence of emerging contaminants such as pharmaceuticals and endocrine disruptors in groundwater supplies, and we are still trying to understand the distribution of naturally-occurring contaminants, such as arsenic in the deltas of south-east Asia (as featured in a recent issue of Nature). These issues highlight the intersection of hydrogeology and public health.

If climate change is your thing, don’t rule out hydrogeology. In addition to questions of water resource availability and changes to recharge patterns in a warmer world with more intense precipitation, hydrogeologists are playing an important role in examining underground injection of carbon dioxide as a potential sequestration technique for reducing atmospheric greenhouse gas concentrations.

Finally, I do have to put in a little plug for my own area of interest. If you like the idea of studying groundwater, but also really like to be able to see what you are working with, and maybe even wade around in it, you should consider focusing on groundwater-surface water interactions. There’s lots of cool research being done to understand how groundwater and surface water interact in streams to affect water quality parameters, aquatic ecosystems, and responsiveness to climatic variability.

If something on my laundry list has appealed to you (or maybe you’re still thinking about the job prospects), what should you do? Take a hydrogeology class, of course. If your university’s geology department doesn’t offer one (which would be unusual), look to civil engineering where water classes are also located. Also make sure that you have a solid background in core geology areas like sedimentology and structure. Consulting firms will expect you to be able to log drill cores and interpret geologic maps. After that, you should consider taking additional water related classes such as contaminant hydrogeology, physical hydrology, groundwater modeling, or mass transport. You should also try to find an internship with a local consulting firm or government agency; that will give you crucial work experience and help you get your feet wet, so to speak. (Caveat emptor though, my career path has been a pretty typical academic trajectory from undergrad through faculty position.)