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Development of hyporheic exchange and nutrient uptake following stream restoration

Next week, the Watershed Hydrology Lab will be well represented at the CUAHSI 2014 Biennial Colloquium. We’ll be presenting four posters, so here come the abstracts…

Development of hyporheic exchange and nutrient uptake following stream restoration

Stuart Baker and Anne Jefferson

Stream restoration is a multi-million dollar industry in Ohio, with major goals of improving water quality and degraded habitat. Yet restoration often falls short of significant improvements in water quality and biodiversity. It is thus important to improve the theory and practice of stream restoration in order to achieve greater benefits per dollar spent, yet there are limited data and understanding of the physical and biogeochemical responses to restoration that constrain the potential for water quality and ecological improvements. Hyporheic exchange, the flow of water into and out of the streambed, is an important stream process that serves critical roles in naturally functioning streams, allowing for stream water to participate with the substrate in various processes. Hyporheic flowpaths can be altered by the transport of fine sediment through the stream bed and are thus susceptible to changes in sediment regime and hydraulics, as well as the changes wrought by construction of a restoration project. The goal of this research is to determine the effectiveness of restoration in enhancing hyporheic flow and associated biogeochemical processes to improve water quality. Preliminary results from Kelsey Creek, OH, a second-order stream restored in August 2013, show a decrease in average hydraulic conductivity but an increase in heterogeneity from pre-restoration (geometric mean 8.47×10-5 m/s, range 1.18×10-6-1.19×10-3) to post-restoration (geometric mean 4.41×10-5 m/s, range 2.67×10-5-3.05×10-4) in piezometer nests through large constructed riffle structures. These piezometers also indicate dominance of downwelling throughout riffle structures with only isolated locations of upwelling. Transient storage and hyporheic exchange will be measured with resazurin injections for comparison between pre-restoration and post-restoration, and nutrient injections of NH4Cl at time points following the restoration will compare the nitrogen uptake rates of the restored reach to an unrestored reach downstream. Additional sites are planned for study to include restoration projects of different ages to examine the development of hyporheic exchange and biogeochemistry after completion of restoration projects.

Congratulations to Darren and Aly!

DarrenCongratulations to Darren Reilly who did a wonderful job defending his MS thesis on Tuesday. Darren’s thesis focused on the identification of groundwater pollution and its sources in rural northeastern Pennsylvania residential water wells. Darren will be preparing his thesis for publication in a journal and is looking for a job in the energy or environmental sectors. Check him out on LinkedIn.

Congratulations also to Alison Reynolds who won first place in the Kent State Undergraduate Research Symposium, Geology/Geography category for her poster on “Sensitivity of precipitation isotope meteoric water lines and seasonal signals to sampling frequency and location.” Aly is a junior this year, and will be continuing to be a valuable member of our research group this summer and next year before heading somewhere fabulous for graduate school.

Congrats Darren and Aly. It is a pleasure to work with such passionate and dedicated students.

A nice British video explaining the connection between rivers and groundwater. I can’t get the embed to work, so you’ll have to click through to watch: This is why I say I study rivers AND groundwater – if you want to understand how water moves through a watershed, you’ve got to …

AGU 2011 abstract: Controls on the hydrologic evolution of Quaternary volcanic landscapes

The following talk will be presented in the 2011 AGU fall meeting session on “EP41F. Posteruptive Processes Operating on Volcanic Landscapes I” on Thursday, December 8th from 9:15 to 9:30 am.

Controls on the hydrologic evolution of Quaternary volcanic landscapes
Anne J. Jefferson and Noemi d’Ozouville

1. Geography and Earth Sciences, University of North Carolina at Charlotte, Charlotte, NC, United States.
2. UMR 7619 Sisyphe CNRS & UPMC, Universite Paris 6, Paris, France.

Conceptual models that explain the evolution of young volcanic landscapes require the prominent inclusion of processes which affect partitioning of water between surface and subsurface flows. Recently emplaced lava flows have no surface drainage, with infiltration to groundwater as the dominant hydrologic process. Older volcanic landscapes are often dominated by extensive drainage networks, fed by permanent or intermittent streams, which have deeply dissected the constructional topography. Drainage density, topography, and stream and groundwater discharge provide readily quantifiable measures of hydrologic and landscape evolution on volcanic chronosequences. We will use examples from the High Cascades, Galapagos, and elsewhere to illustrate the trajectories and timescales of hydrologic evolution.

We suggest that the surface-subsurface water partitioning is a function of volcanic architecture, climate-driven processes, and water-rock interactions. We will show that in mafic volcanic areas, climate-driven processes (such as weathering and dust deposition) control landscape evolution, while explosive eruptive products may be important for local hydrology. In the High Cascades, where precipitation exceeds 2 m/yr, landscape dissection has obliterated constructional morphology within 1 million years, while in the more arid Galapagos, million year old landscapes are largely undissected. Conversely, localized groundwater perching on pyroclastic layers or paleosols has been characterized in the Galapagos, but not in the Cascades, where pyroclastic activity is more limited in extent. In areas where explosive activity, including phreatomagmatism, dominates volcanism, the evolution of hydrology and topography occurs much more rapidly than in landscapes created by effusion. Hydrothermal circulation and water-rock interactions may play an important role in reducing deep permeability and altering subsurface flowpaths in some volcanic landscapes. Observed chronosequences can be complicated by juxtaposition of different age deposits, post-emplacement faulting, uplift or subsidence, and climate change, so detailed understanding of the landscape’s geologic history is a prerequisite for appropriate interpretation of hydrologic evolution in volcanic landscapes.

Lush vegetation in a pit crater on Santa Cruz Island

A "pit crater" in the highlands of Santa Cruz Island in the Galapagos shows preferential vegetation growth at the contact between lava flows, probably where water is more available. Photo by A. Jefferson.

Ralph McGee and Cameron Moore will graduate next week!

Major congratulations to two Watershed Hydrogeology Lab graduate students who have finished writing their MS theses and will defend them next week. Ralph McGee and Cameron Moore both started in our MS in Earth Science program in August 2009, and less than two years later they have each completed impressive MS projects on headwater streams in Redlair Forest of the North Carolina Piedmont.

Ralph McGee will present his research on “Hydrogeomorphic processes influencing ephemeral streams in forested watersheds of the southeastern Piedmont U.S.A.” on Thursday, May 12th at 10:00 am in McEniry Hall, room 111 on the UNC Charlotte campus.

The unofficial title for Ralph’s work is “Tiny Torrents Tell Tall Tales.” Watch the video below to see why.

Cameron Moore will present his research on “Surface/Groundwater Interactions and Sediment Characteristics of Headwater Streams in the Piedmont of North Carolina” on Friday, May 13th at 9:00 am in McEniry Hall, room 111 on the UNC Charlotte campus.

When Cameron started working on this project, I had thought that the story would focus on how fractured bedrock contributed to groundwater upwelling in the streams, but it turns out the small debris jams (like the one below) are the dominant driver of groundwater/stream interactions and spatial variability of channel morphology.

Debris jam in Deep Creek

Looking upstream at a debris jam in Deep Creek

Faculty, students, and the public are encouraged to attend the presentations and ask Ralph and Cameron any questions they may have.

Geology is destiny: globally mapping permeability by rock type

Cross-posted at Highly Allochthonous

Permeability (the ease with which a fluid moves through a material) is the ultimate goal of many hydrogeologic investigations, because without that information it is impossible to quantify subsurface water and heat flow rates or understand contaminant transport. Yet permeability is notoriously difficult to quantify, both at the local-scale and the landscape-scale. Permeability varies over 13 orders of magnitude across rock and sediment types, because of differences in pore sizes, geometry, and connectedness. Loose gravel could have permeability as high as 10-7 m2, but unfractured igenous and metamorphic rocks could be as low as 10-20 m2. The diagram below is an example of the sort of relationship between rock type and permeability shown near the beginning of every major hydrogeology textbook.

Typical ranges of permeability for different rock types, usually based on hydraulic measurements made at wells.

Typical ranges of permeability for different rock types, usually based on hydraulic measurements made at wells.

Most of the time, hydrogeologists are happy to just to get permeability to within an order of magnitude or two. Knowing permeability is not just useful for those interested in in water supply problems and transport of contaminants. For scientists who model watersheds or land-atmosphere interactions in climate models, being able to easily estimate landscape-scale permeability would be incredibly helpful.

In a new paper in Geophysical Research Letters, scientists from Canada, Germany, the Netherlands, and the US have just done a big favor for those scientists. Gleeson et al. (2010) compiled the first regional-scale maps of permeability for the North American continent and the terrestrial globe. They are interested in permeability in the uppermost 100 m of the subsurface, but below the water table, where all pore spaces are saturated with water. They defined regional-scale as greater than 5 km, because they wanted to avoid influences by things like individual fractures. Using previously published hydrogeologic models, in which permeability was calibrated against groundwater flow, tracers, or heat fluxes, Gleeson and colleagues identified permeability values for 230 hydrogeologic units, grouping them into seven “hydrolithologic” categories, by rock type.

The scientists compared the permeability values from the models to the expected permeabilities for each rock type based on smaller-scale measurements (like those used to make the graph above), and they found reasonably good correspondence. They also examined whether permeability values within each hydrolithologic category were correlated with the scale of the model used to generate them. They found that permeability was scale-independent above 5 km, except in carbonates, where large karst features may result in changing permeability with increasing area.

Using pre-existing geologic maps for North America and the world, Gleeson and colleagues divided the Earth into their hydrolithologic categories. For each category, they calculated the geometric mean of the modeled permeability values, and applied that mean permeability to all of the map units in that category. The resultant maps show the distribution of permeability across the land surface.

Portion of Figure 3c from Gleeson et al. (2010, Geophysical Research Letters).

Portion of Figure 3c from Gleeson et al. (2010, Geophysical Research Letters) showing the permeability distribution across North America. North of the dashed line is continuous permafrost and in that region, the map likely significantly over-estimates permeability.

The global map uses a single geology dataset, so there are no weird boundaries in the data, but it is of coarse resolution. The North American map (shown above) is at much finer resolution (75 km2 mean polygon area, with 262,111 polygons), but it has a few odd edges that correspond to state and national borders. The authors point to these boundary problems in their discussion of caveats, along with the problems associated with permafrost, deep unsaturated zones in arid areas, and deep weathering in the tropics. In addition, the use of a single permeability value for each category will necessarily lump together some terrains with similar rock types but differing geologic histories and resultant permeabilities (e.g., the High and Western Cascades in Oregon).

The work of Gleeson and colleagues represents an important first step in translating regional-scale geologic data into permeability fields. These maps will be useful for continental-scale and larger earth system models and for data sparse regions. Their methodology also raises some interesting possibilities for subdividing the hydrolithologic categories in areas where there are more hydrogeologic model data available, but where there hasn’t been comprehensive hydrogeologic modeling. Finally, their finding that regional-scale model values are in accord with the ranges reported in every hydrogeology textbook is a significant confirmation of the fall-back position of many students of hydrogeology: “If you have no data from wells in your field area, use a textbook to estimate permeability from the rock type.”

Gleeson, T., Smith, L., Moosdorf, N., Hartmann, J., Dürr, H., Manning, A., van Beek, L., & Jellinek, A. (2011). Mapping permeability over the surface of the Earth Geophysical Research Letters, 38 (2) DOI: 10.1029/2010GL045565

AGU Abstract: Spatial heterogeneity in isotopic signatures of baseflow in small watersheds: implications for understanding watershed hydrology

In a few weeks, I’ll be giving the following talk at the American Geophysical Union Fall Meeting in a session on Groundwater/Surface Water Interactions: Dynamics and Patterns Across Spatial and Temporal Scales. My talk will be in Moscone West 3014 at 11:05 am on Wednesday, December 15th, 2010.

Spatial heterogeneity in isotopic signatures of baseflow in small watersheds: implications for understanding watershed hydrology
A. J. Jefferson

Time series of stable isotopes of oxygen and hydrogen in stream water are widely used to characterize watershed transit times and flowpaths, but synoptic sampling of multiple locations within a watershed can also provide useful information about heterogeneity of stream water sources and groundwater-surface water interactions that may affect interpretations of watershed hydrology. Here I present results of same-day baseflow sampling campaigns in low-relief, 0.1 to 100 km2 watersheds. More than half of less than 5 km2 forested and urban watersheds sampled in this study had variability in ?2H exceeding 2‰ and ?18O variability exceeding 1‰, substantially larger than the analytical uncertainty. In some cases, the heterogeneity was extreme, with ?2H varying by >10‰ over 150 m in one stream. Some isotopic perturbations occur in conjunction with stream conductivity and temperature changes, and such zones likely reflect localized contributions from fractured crystalline bedrock. In the urban 100 km2 watershed, mainstem baseflow isotopes were relatively homogeneous, but ?2H varied by more than 10‰ across tributaries, suggesting that subwatersheds are fed by water with different sources or transit times. Some urban streams were isotopically similar to the municipal water supply, suggesting that water main leakage and wastewater discharge may be locally significant contributors to baseflow. The isotopic heterogeneity of small streams and watersheds suggests that an understanding of groundwater-stream interactions is needed to correctly interpret isotope-based inferences about watershed transit times and flowpaths.

Castle Geology

Cross-posted at Highly Allochthonous

Being a giant geo-nerd, I tend to pepper my travels with a lot of geologically or hydrologically interesting places. A recent trip brought me to the UK and included a meetup with my Highly Allochthonous coblogger in Edinburgh. Being an American tourist, I also felt compelled to visit at least one castle during my time in the UK, so I dragged Chris to Edinburgh Castle…where we naturally we ended up talking about the geology.

Edinburgh Castle from Princes Street

Edinburgh Castle from Princes Street. The low area with gardens in the foreground used to be a loch/lake. (Photo by A. Jefferson)

First off, Edinburgh Castle sits atop the core of a Carboniferous (340 million year old) volcano, now called Castle Rock. The rock is impressively elevated above the surrounding glacially sculpted cityscape. The volcanic root formed a bit of a speed bump for Pleistocene glaciers moving from west to east. Castle Rock was more erosion resistant than surrounding sedimentary rocks, so it was left standing higher than the surroundings. But it also protected the sedimentary rocks in its lee – forming a giant crag and tail structure. The Royal Mile, which stretches from the Castle to Holyrood Palace rides on the tail of this structure – which gradually decreases in height and width away from the castle. In the Google Earth image below, I’ve maximized the vertical exaggeration and you can get some sense of it, though I can tell you that a more visceral understanding is achieved by walking up or down the Royal Mile.

Crag and tail of Edinburgh Castle and the Royal Mile

Crag and tail of Edinburgh Castle and the Royal Mile (image from Google Earth)

Within the castle itself, the glacial legacy is on display in the building stones, which show a remarkable diversity of lithologies, both those found locally and those farther afield in Scotland. It is likely that castle builders would have made use of the rocks left on the landscape when the glaciers retreated, but the ice caps would have given them plenty of variety. In the middle of the photo below, I think we are looking at the Old Red Sandstone, which has an important place in the history of geology and of paleontology.

Stonework on St. Margaret's Chapel, the oldest extant building in Edinburgh Castle

Stonework on St. Margaret's Chapel, the oldest extant building in Edinburgh Castle (photo by A. Jefferson)

The stone construction seemed to vary between buildings and even parts of buildings within the castle. The photo above is from St. Margaret’s Chapel, built in the 12th century, and you can clearly see how the big rocks are matrix-supported by a sand and gravel cement. This wall is actually even different from other walls on the same building, where stones are much more rectangular, probably cut, and there is much less matrix, as shown in the photo below. The informative castle guidebook suggests that the wall pictured above may have been originally part of another structure, onto which St. Margaret’s chapel was built adjointly. I should also point out that the walls in St. Margaret’s chapel are incredibly thick (1 m or more), so there’s a lot of stone work we’re not even seeing from the outside.

St. Margaret's chapel showing variety of stone work

St. Margaret's chapel showing variety of stone work (photo by A. Jefferson)

Portcullis Gate and the Argyle Tower

Portcullis Gate and the Argyle Tower (photo by A. Jefferson)

In other parts of the castle, and indeed in the surrounding city, it was fun to watch for places where old doorways or windows had been filled in or where additions had been added to stone buildings. These were usually pretty easily spotted by a change in the stone construction style. For example, in the photo on the left, you can see the main gated entrance to the castle (the Portcullis Gate), which was constructed in the late 16th century. On top of it is the Argyle Tower, one of the youngest buildings in the castle, constructed in 1887. To me it also looks like there might be an intermediate strata between the cut and tightly placed blocks immediately around the gate and the much more modern top part.

Wall adjacent to Lang Stairs

Wall adjacent to Lang Stairs. The plaque on the wall commemorates the successful recapture of the castle from the English in 1314. (photo by A. Jefferson)

One of the most impressive features of the castle was the way the stone architecture worked with the irregular topography of the bedrock surface. Walls had uneven bottoms, and even, in some places, sides, like this wall near the Lang Stairs.

Finally, I would be remiss if I didn’t point out one important hydrogeological influence on Edinburgh Castle and its history. As I mentioned, the castle is much higher than the surrounding topography (peak is 134 m above sea level) and made of dense volcanic rock. This has advantages from the defensive point of view, but a significant disadvantage from the “having enough water to stay alive” point of view. During peace times, castle residents presumably brought water up the hill from the loch or from wells in town. But during sieges, they were reliant on the Fore Well. This well, constructed in the 14th century, is an impressive 34 m deep (through solid rock! in the 14th century!), but only the bottom 3 m of the well are below the water table. The well could provide 11,000 liters – but that’s not a lot to supply a bunch of soldiers and their animals. During at least one siege, most of the deaths seem to be attributable to lack of adequate water, rather than the warfare itself.

So that’s what happens when you take an American geo/hydro nerd to Scotland…she looks at castles and thinks about rocks and water.

New publication: Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA

How does a landscape go from looking like this…

<2000 year old landscape on basaltic lava with no surface drainage

~1500 year old basaltic lava landscape with no surface drainage

to looking like this?

2 Million year old landscape on basaltic lava

2 Million year old landscape on basaltic lava. Note steep slopes and incised valleys

Find out in my new paper in Earth Surface Processes and Landforms.

Hint: Using a chronosequence of watersheds in the Oregon Cascades, we argue that the rates and processes of landscape evolution are driven by whether the water sinks into the lava flows and moves slowly toward springs with steady hydrographs or whether the water moves quickly through the shallow subsurface and creates streams with flashy hydrographs. Further, we suggest that this water routing is controlled by an elusive landscape-scale permeability which decreases over time as processes like chemical weathering create soil and clog up pores in the rock. And as a bonus, because of the high initial permeability of basaltic landscapes, the formation of stream networks and the dissection of the landscape appears to take far longer than in places with less permeable lithologies.

Jefferson, A., Grant, G., Lewis, S., & Lancaster, S. (2010). Coevolution of hydrology and topography on a basalt landscape in the Oregon Cascade Range, USA Earth Surface Processes and Landforms, 35 (7), 803-816 DOI: 10.1002/esp.1976