In July 2011, Anne was a plenary speaker at the Chapman Conference on The Galápagos as a Laboratory for the Earth Sciences in Puerto Ayora, Galapágos. Anne was tasked with reviewing the state-of-knowledge of volcanic island hydrology and identifying pressing questions for future research in this 40 minute talk. The following is the abstract which she submitted when she began the task.

Top down or bottom up? Volcanic history, climate, and the hydrologic evolution of volcanic landscapes

Volcanic landscapes are well suited for observing changes in hydrologic processes over time, because they can be absolutely dated and island chains segregate surfaces of differing age. The hydrology of mafic volcanic landscapes evolves from recently emplaced lava flows with no surface drainage, toward extensive stream networks and deeply dissected topography. Groundwater, a significant component of the hydrologic system in young landscapes, may become less abundant over time. Drainage density, topography, and stream and groundwater discharge provide readily quantifiable measures of hydrologic and landscape evolution on volcanic chronosequences. In the Oregon Cascades, for example, the surface drainage network is created and becomes deeply incised over the same million-year timescale at which springs disappear from the landscape. But chronosequence studies are of limited value if they are not closely tied to the processes setting the initial conditions and driving hydrologic evolution over time.

Landscape dissection occurs primarily by erosion from overland flow, which is absent or limited in young, mafic landscapes. Thus, volcano hydrology requires conceptual models that explain landscape evolution in terms of processes which affect partitioning of water between surface and subsurface flows. Multiple conceptual models have been proposed to explain hydrologic partitioning and evolution of volcanic landscapes, invoking both bottom up (e.g., hydrothermal alteration) and top down processes (e.g., soil development). I suggest that hydrologic characteristics of volcanic islands and arcs are a function of two factors: volcanic history and climate. We have only begun to characterize the relative importance of these two drivers in setting the hydrologic characteristics of volcanic landscapes of varying age and geologic and climatic settings.

Detailed studies of individual volcanoes have identified dikes and sills as barriers to groundwater and lava flow contacts as preferential zones of groundwater movement. Erosion between eruptive episodes and deposits from multiple eruptive centers can complicate spatial patterns of groundwater flow, and hydrothermal alteration can reduce permeability, decreasing deep groundwater circulation over time. Size and abundance of tephra may be a major geologic determinant of groundwater/surface water partitioning, while flank collapse can introduce knickpoints that drive landscape dissection. The combination of these volcanic controls will set initial conditions for the hydrology and drive bottom up evolutionary processes.

Climatic forcing drives many top down processes, but understanding the relative effectiveness of these processes in propelling hydrologic evolution requires broader cross-site comparisons. The extent of weathering may be a major control on whether water infiltrates vertically or moves laterally, and we know weathering rates increase until precipitation exceeds evapotranspiration. Weathering by plant roots initially increases porosity, but accumulation of weathered materials, such as clays in soils, can reduce near-surface permeability and promote overland flow. Similarly, eolian or glacial inputs may create low permeability covers on volcanic landscapes.

View into the crater of Sierra Negra Volcano on Isabella Island, Galapagos

View of the 2005 lava inside the crater of Sierra Negra Volcano on Isabella Island, Galapagos. Photo by A. Jefferson

Posted by: Anne Jefferson | September 17, 2011

About the best compliment I could get (or, why blogging is worthwhile)

Amateur geologist, author, and fantastic human being, Dana Hunter, has written a post in which she talks about how my blogging has inspired an appreciation for hydrology that she never otherwise would have developed. I won’t quote from her post here, but I wanted to bookmark it someplace special so that I could come back to it when the demands of teaching, research, and parenting get me down. If nothing else, I now know my blogging has made a difference for somebody that I’ve never even met.

I think that’s part of the power of blogging – it not only can bring the world into the classroom, but it broadens the classroom into the world. As the theme for this month’s geoscience blog carnival, the Accretionary Wedge, I asked contributors to muse on education. Amongst many great submissions so far, Dana’s post on how professional geoscientists can reach out to amateurs is truly inspiring. Honestly, if geoscientists are truly going to make a difference in the world, it won’t be through journal papers, conference presentations, or even graduate seminars, it’ll be through reaching out beyond our professional and student ranks to people who are curious and care about the Earth. I sincerely hope that includes most of its residents.

Cynthia Barnett

Cynthia Barnett (photo supplied by Ms. Barnett)

I’m excited to announce that Cynthia Barnett will be speaking on campus next week. She’s an outstanding thinker and writer about water conservation, particularly as it pertains to the eastern United States, where our sense of water-richness has lulled us into complacency.

From the press release:

Award-winning journalist and author Cynthia Barnett will visit UNC Charlotte to discuss water ethic for America at 7 p.m., Wednesday, Sept. 21, in the College of Health and Human Services, Room 128.

Barnett’s talk is the first stop for a tour about the book “Blue Revolution: Unmaking America’s Water Crisis,” scheduled for national release Sept. 20. “Blue Revolution” is said to be the first book to call for a national water ethic. Barnett uses the Catawba River as an example to illustrate the important role that water plays in America’s energy supply. The book combines investigative reporting with solutions from across the country and the globe to show how communities and nations have come together in a shared ethic to reduce consumption and live within their water means.

Barnett also is the author of “Mirage: Florida and the Vanishing Water of the Eastern U.S.” A veteran journalist, she won the national Sigma Delta Chi prize for investigative magazine reporting and a gold medal for best nonfiction in Florida book awards.  A book signing follows this free, public presentation, which is cosponsored by the UNC Charlotte Ethics Center, IDEAS Center and the Department of Geography and Earth Sciences.

BlueRevolutionCoverCynthia will also be available to meet with students and faculty in CHHS 128 from 4 to 5 pm. Please stop by, say hi, and ask your water questions.

I’m currently devouring a copy of Cynthia’s new book, so look for a review of the book here or elsewhere in the coming weeks.

Snowline near Skykomish, Washington (photo on Flickr by RoguePoet, used under Creative Commons)

Snowline near Skykomish, Washington (photo on Flickr by RoguePoet, used under Creative Commons)

Jefferson, A. 2011. Seasonal versus transient snow and the elevation dependence of climate sensitivity in maritime mountainous regions, Geophysical Research Letters, 38, L16402, doi:10.1029/2011GL048346.

Abstract:

In maritime mountainous regions, the phase of winter precipitation is elevation dependent, and in watersheds receiving both rain and snow, hydrologic impacts of climate change are less straightforward than in snowmelt-dominated systems. Here, 29 Pacific Northwest watersheds illustrate how distribution of seasonal snow, transient snow, and winter rain mediates sensitivity to 20th century warming. Watersheds with >50% of their area in the seasonal snow zone had significant (α ≤ 0.1) trends towards greater winter and lower summer discharge, while lower elevations had no consistent trends. In seasonal snow-dominated watersheds, runoff occurs 22–27 days earlier and minimum flows are 5–9% lower than in 1962, based on Sen’s slope over the period. Trends in peak streamflow depend on whether watershed area susceptible to rain-on-snow events is increasing or decreasing. Delineation of elevation-dependent snow zones identifies climate sensitivity of maritime mountainous watersheds and enables planning for water and ecosystem impacts of climate change.

Posted by: Anne Jefferson | August 27, 2011

Scenic Saturday: Ropy pahoehoe on a biogenic beach

Cross-posted at Highly Allochthonous

Anne on a ropy pahoehoe flow on the beach

Anne enjoying the scenery on Isabella Island, Galápagos, July 2011

In this inaugural Scenic Saturday post, I offer up very happy volcano/landscape nerd enjoying the stunning geologic scenery on Isabella, Galápagos Islands, July 2011. I was there as a participant in the Chapman Conference on the Galápagos as a Laboratory for the Earth Sciences. I may manage to blog in more detail about the islands and the conference, but for now enjoy the scenery, just as I did on my first few days in the archipelago.

In the image above, I’ve got my back to the village of Villamil, on the southern flank of Sierra Negra volcano, and I’m actually sitting on some of the oldest exposed lavas from that volcano. You’re looking at the crust of a pahoehoe flow that is probably about 5000 to 9000 years old. A short distance up the beach, I could peek under the skin of the lava and walk a few meters into a lava tube. The floor of this lava tube was below sea level and covered by sea water, so this was really a chance to experience the water table in a very macro-pore.

Lava tube, geologist for scale

Lava tube, USGS scientist for scale. Isabella Island, Galápagos, July 2011

The lava along this stretch of seafront is largely covered by sand that is clearly not basaltic. Instead it is made of little bits of broken shells and sea urchins from the incredibly rich marine ecosystem that surrounds the islands.

Beach sediments

Beach close-up, near Villamil, Isabella Island, Galápagos, July 2011

Elsewhere, the biogenic beach was covered by rather more living parts of the marine ecosystem. This sea lion put on a quite a performance for some appreciative visitors to a mangrove lagoon (and freshwater spring).

Isabella 105

Sea lion, sand, and mangrove roots, near Villamil, Isabella Island, Galápagos, July 2011

Posted by: Anne Jefferson | July 3, 2011

Flooding around the world (3 July edition)

Cross-posted at Highly Allochthonous

Here is a brief update on the floods I covered in the last edition of flooding around the world. Note that there has also been flooding in Xiengkoung, Viengtian, Boolikhamxay, and Xayaboury provinces of Laos, as a result of heavy rainfall from a tropical storm; in Russia’s Khabarovsk region (Kiya and Khor rivers), from heavy rainfall; and in the Philippines’ Davao city, from heavy rainfall.

China and the Yangtze River

The U.S. Corps of Engineers increased the output of the Gavins Point Dam spillway to 150, 000 cubic feet per second June 14, 2011. The flow was increased to help regulate the Missouri River due to record snow and rain fall earlier this year. (SDNG photo by Master Sgt. Donald Matthews)

Flow from the Gavins Point Dam spillway was 150, 000 cubic feet per second on June 14, 2011. (SDNG photo by Master Sgt. Donald Matthews, image on Flickr)

Missouri River

The Souris River, continues to flow over Minot, N.D. flood levees June 23, as the water begins to inundate residential neighborhoods. (DoD photo by Senior Master Sgt. David H. Lipp)

The Souris River, continues to flow over Minot, N.D. flood levees June 23, as the water begins to inundate residential neighborhoods. (DoD photo by Senior Master Sgt. David H. Lipp, image from Flickr)

Souris River

Posted by: Anne Jefferson | June 26, 2011

Flooding around the world (26 June edition)

Cross-posted at Highly Allochthonous

Since the last edition of flooding around the world, flooding along the Mississippi River has mostly subsided, but flooding continues along the Missouri River and in China. Several new flood wetspots have also popped up, as the image below from The Flood Observatory (at the University of Colorado) depicts.

Current flooding, image from The Flood Observatory (http://floodobservatory.colorado.edu/)

Current flooding, image from The Flood Observatory (http://floodobservatory.colorado.edu/)

The big stories are flooding in China, along the Missouri River, and on the Souris River in Saskatchewan and North Dakota. The best summary I’ve seen is by Jeff Masters of Weather Underground, who gets straight to the story in his headline: “Floods overwhelm North Dakota levees; floods kill 175 in China”. The Flood Observatory also has a handy table that includes flood cause, duration, and a snippet of recent news for each of the flood events pictured on the image above.

TRMM measured precipitation over China, June 13-19, 2011 (NASA image)

TRMM measured precipitation over China, June 13-19, 2011 (NASA image)

China

Flooding continues in central and southern China’s Zhejiang, Jiangsu, Anhui, Jiangxi, Hubei, Hunan and Guangdong provinces, and in parts of the northwest Gansu Province (though drought is still the more dominant threat there).

NOAA Hydrologist Steve Buan just took this photo from Broadway Bridge looking upstream in #Minot, ND  via Justin Kenney on Twitpic

NOAA Hydrologist Steve Buan took this photo on 25 June from Broadway Bridge looking upstream in Minot, ND, via Justin Kenney on Twitpic

The Souris River and Minot, North Dakota

More than 11,000 people have been evacuated and more than 4000 homes inundated in record-breaking flooding in Minot, North Dakota and surrounding communities. Levees in Minot were over-topped, even after emergency preparations by the Corps of Engineers. The river crested yesterday about 2 m above major flood stage, but will remain extremely high for a few more days.

  • Where is the Souris River? It is not part of the Missouri basin. No, as the map below shows, the Souris is part of the Assiniboine River River watershed. The Red River, which flooded earlier this year also drains to the Assiniboine, but the currently flooding Souris doesn’t have the same lake bottom geologic history as the Red.
  • Map of the Souris River and related watersheds, from Wikipedia

    Map of the Souris River and related watersheds, from Wikipedia

  • Why is there flooding?The seeds of the record floods along the Souris and Missouri Rivers were sown beginning last summer, with persistent heavy rains (that lead to flooding), a wet fall, a snowy winter, and then another very wet spring.
  • What’s it like in Minot right now?The city is effectually split in half by the flooding, with 1 in 3 residents is evacuated. It is unclear whether the municipal water supply of Minot and a nearby Air Force base has been contaminated, so the city is under a boil water order. (CNN wire report, 26 June). Residents in unflooded portions of town and surrounding areas are doing what they can to shelter the evacuees and take care of the belongings they got out before the flood arrived. (AP, 26 June)
  • Are there problems anywhere else on the river?Yes, the flood has displaced hundreds in southeastern Saskatchewan, upstream of North Dakota (CBC, 20 June). Floodwaters in that area are now receding (Montreal Gazette, 25 June). Downstream of North Dakota, residents along the Souris River in Manitoba are working to build up their defenses, because the flood will be there in less than two weeks. (Toronto Sun, 25 June). This new flooding arrives on top of already a record-breaking year for floods for the province, with $1 billion in damages already and 3 million acres of farmland still soaked and unplantable (UPI, 22 June).
  • Are there any good pictures of the flooding?The Sacramento Bee had a striking collection of photos on Friday, 24 June. A lot of the news stories linked to above have photos, NASA’s Earth Observatory has an event page with four sets of images so far, and I’d be really surprised if the other big photo news blogs didn’t have a set of images at some point in the next few days.
Holt County Levee District No. 10, a non-federal levee near Rulo, Neb., experienced an overtopping breach June 18, 2011, flooding U.S. Route 159 and the surrounding area. Photo by Diana Fredlund, US Army Corps of Engineers. Image from Flickr.

Flooding from the breach of a non-federal levee near Rulo, Nebraska on 19 June. The levee overtopped and breached on 18 June 2011, flooding U.S. Route 159 and the surrounding area. Photo by Diana Fredlund, US Army Corps of Engineers. Image from Flickr.

Missouri River

Record flooding continues to move downstream in the Missouri River system. Heavy snowpacks and a lot of rain in the Upper Missouri have forced unprecedented releases of water from the dams along the river in the Dakotas. Right now, the biggest flood problems seem to be in Missouri and Iowa, but high water and evacuated areas are stretched all along the river, and the flood won’t fully recede for months. The National Weather Service has a flooding information page set up, with regular updates.

  • How has the flood been affected by the dams along the Missouri River? There’s a lot of public debate over whether the Corps of Engineers management plan for the river favors upper basin states’ desires to keep their reservoirs full over the flood-control needs of downstream states. (KC Monitor, 25 June) People are asking why the Corps didn’t release more water earlier this year, in order to prevent such massive releases now. But, flood prediction models couldn’t have forecast the week after week of heavy rain that fell this spring. Still, I expect people and politicians (especially in the lower basin) to keep talking about this as long as the flood and its cleanup lasts. Here’s an editorial from the Des Moines Register (25 June) that tries to put things in perspective.
  • How are the levees? “A total of four levees in Missouri have been breached along the Missouri River, according to officials with the U.S. Army Corps of Engineers in Kansas City. The epicenter of the flooding in Missouri is located in Holt County, where two levees have been overtopped and two levees have been breached by raging water flowing down from a reservoir in South Dakota. ” (KC Monitor, 25 June) There have also been levee breaches in multiple places on the Iowa side of the river (Reuters, 25 June).
  • What about the nuclear plants? Two Nebraska nuclear plants are in the path of Missouri flood waters, but emergency levees are 0.6 m higher than the expected crest at the Fort Calhoun plant (Omaha World-Herald, 17 June) and 2 m higher than the expected crest at the Cooper station (Chicago Tribune, 25 June). [Update: 6:30 pm 26 June: While I was writing this post, news wires reported than a temporary berm around the Fort Calhoun plant breached last night. Two feet of water now surround reactor buildings, but the reactor systems were unaffected and inside water-tight buildings. (Reuters)] Charmingly, residents near the plants are unconcerned, according to the Chicago Tribune story.
  • What does the flood look like from above? NASA’s Earth Observatory has 9 satellite images of the flood, so far. There’s also a nice video taken on 9 June from a low-altitude airplane, by KETV news.

Open Thread

Please use the comment thread below to add links to updated news stories, videos, or imagery about any floods that are occurring in the next few weeks. I’ll write another flood update in mid-July. If there are particular floods you are interested in, or if you’d like me to delve more into the hydrological details, please let me know.

Tidbits temperature probeNote: I use stream temperature to understand groundwater-stream interactions and the response of streams to urbanization. Since ~2004, my stream temperature probe of choice has been the Tidbits temp probe, manufactured by Onset corporation. I like them because they are +/-0.2C and extremely durable, watertight, and reliable. Plus, I’ve had good customer service experiences with the manufacturer. What follows is my attempt to explain how I deploy them in the field, based on my cumulative experience and what I’ve learned from others. Please comment and add your own ideas and experiences, and I’ll amend the protocol as needed.

Getting ready for the field

  1. Obtain Tidbits temperature probes and the associated HoboWare Pro software. Read the documentation and learn how they work.
  2. Using the delayed start feature in Hoboware, set all of the temperature probes to start at the same time and at the same sampling interval. I like to set them to start evenly on the hour. It makes analysis easier later.
  3. You can’t change the calibration of the temperature probes within the software, and they should come pre-calibrated, but you should still check the calibration of your temperature probes relative to a certified thermometer and to each other. I recommend a 3 stage calibration check process, but you’ll want to do at least 2 temperatures that bracket the range of range conditions you expect to measure. You need to do each of these for a couple of hours, because while the response time in water is ~5 minutes, it is slower in air.
    • An ice bath (with stirring) or the refrigerator.
    • Room temperature, out of direct light, in a room with fairly stable temperatures for a couple of hours.
    • Depending on what temperature your streams are likely to be, you might want a temperature intermediate between the refrigerator and room temperature. (I’d love to hear your suggestions for an easy, good intermediate cool temperature.)
    • Or, if you are interested in summer headwater stream temperatures, you could use something like a consistenly shady area outside. I’ve also used my backpack, by putting all of the probes in the same container inside it, and then hiking around with them for several hours prior to installation.
  4. Download the Tidbits after the calibration check, and reset them for a simultaneous start on the day you’ll be deploying them in the field. I’ve used a 15 minute interval for projects where daily and seasonal fluctuations were of interest; but since we are now interested in storm response, I think we should set them to log at 5 minute intervals (in Celsius, please!).
  5. If there are extra tidbits available, I recommend deploying one in the air, in a shady area near the stream at each field site. I’ve hung them from a tree branch with fishing line, and a homebuilt radiation shield. My radiation shield was a gallon milk jug with the bottom cut off. The tidbit fit through the top opening, and then I screwed the top back on, so that the Tidbit hung freely within an area shaded on the top and sides by the milk jug.

Selecting your field site

There are several very important things to consider when selecting your probe site. You are probably going to have to compromise somewhere in this list at some of your sites, but this is what to strive for.

  1. It meets your scientific objectives (i.e., is positioned appropriately relative to a stormwater BMP, restoration structure, tributary junction, or other field sampling/equipment site.)
  2. The probe will be under flowing water under a wide range of flow conditions. Good places include the channel thalweg or a pool that will not go stagnant (e.g., below a rock outcrop or structure that directs all streamflow into the pool).
  3. The probe will out of direct sunlight at all times of day, as best as possible. Deep shade, an overhanging bank, or an incised reach is good. Peak water temperatures occur in the mid- to late-afternoon, so this is the most important time to check and make sure your site is out of the sun. Adding a cobble on top of your probe, without completely burying the probe in the streambed, is another good way to keep the sun off of it (and to make it less likely to be discovered or banged up during high flow). If you think sun exposure is likely to be a problem (or your data suggest that it is), you should take measurements of shading with a densiometer. Measuring shading won’t fix the problem, but at least you’ll be able to discuss it.
  4. The probe placement is as geomorphically consistent with other probes in the project as possible.
  5. The probe can be discretely and securely attach the probe to something very stable. I’ve almost always used streamside trees, but a post holding other equipment would work too.
  6. The probe should be located somewhere it is possible to bring it up onto the bank while still cabled, so that the Tidbit can be downloaded into the laptop without having to balance the laptop in the middle of the stream.

Deploying the probe

  1. Loop steel cable through the hole on the Tidbit, and crimp the loop shut with a hand swager (like this one). I have cabling, crimps, a swager, and a cable cutter available in my lab.
  2. Measure out an appropriate length of cable to reach the secure attachment site, loop around it, and cut and crimp the cable. I like to give the cable enough room so that it can lie flush with the stream bed and bank and let the probe be in the thalweg, under a rock, but I try not to give it too much slack to get caught on things or let the probe go banging down the stream if it gets dislodged. And, of course, I never make a loop around a tree very tight
  3. Put the probe in the stream. If possible, place a cobble on top of it so that water flows under the cobble and the probe doesn’t get smooshed into the streambed.
  4. Mark your field site with (1) GPS coordinates, (2) discrete flagging or a stake, (3) write down really good field notes describing the site and how you got there, and (4) take photos of everything (like the ones below). Write your field notes so that your advisor(s) can find the site 2 years from now without your help. (Thanks!)

Note: We have tried a variety of methods for securely attaching the Tidbits temperature probes to a fixed object. Rope gets abraded, degraded, and eventually breaks in high turbulence and velocity flows. High test fishing line broke as well during a high flow in a first order stream. We have settled on steel cable, thin enough to thread through the hole of the Tidbits and secured by crimping, as shown below. Recently, we discovered that several of the cables that had been deployed for ~2 years had rusted and broken and that we’d lost the temperature probes at some point since we’d last downloaded their data. I’ve now heard that some people are using plastic coated steel wire. Maybe we should consider that as an alternative to the unocated cable.

I still believe that the steel cabling is a good attachment method, but our experience reminds me of the importance of regularly checking on field equipment. Even if the temperature probe can collect a year’s worth of data before its memory fills up, I’d recommend downloading the data at least once every 3 months (in a non-flashy stream) and doing a thorough check of the cable integrity each time. In urban streams, I now recommend downloading table and checking cable integrity every 2 weeks. Data from a lost probe can never be recovered.

DC12-Tidbits-attach

Attachment for temperature probe at Deep Creek site DC 12, during the fishing line-era of installation. The flagging was also labeled with a project and site identifier.

The Tidbits is under the triangular rock at the center of the photo.

The Tidbits is under the triangular rock at the center of the photo. You might be able to see the line extending to it. Good points about this site: A rock protector with good water flow under and around it and good shading. Bad points: Not a lot of flow depth here, but we were at the seep initiating this stream. We had an air temperature probe at this site as well, and the water temperature was always significantly muted relative to the air temperature fluctuations.

Thanks to Sarah Lewis for adding her wise comments to via email. She taught me a lot of this stuff in the first place!

Cross-posted at Highly Allochthonous (for obvious reasons)

ResearchBlogging.org Allochthonous may have some obscure usage related to rocks, but in ecology, allochthonous material is a major concept that underpins thinking about nutrient cycling and food web dynamics. In its most general definition, allochthonous material is something imported into an ecosystem from outside of it. Usually, ecologists are thinking about organic matter and the nutrients (C, N, and P) that come with it.

Allochthonous material in the form of coarse particulate organic matter in a mountain stream in Oregon.

Allochthonous material in the form of coarse particulate organic matter in a mountain stream in Oregon.

In streams, allochthonous material includes leaves that fall or are washed into the water and branches and trees that topple into the stream. These would both be called “coarse particulate organic matter” or “CPOM” in the lingo of stream ecologists. In headwater streams, especially in forested areas, there is a lot of CPOM, and the community of aquatic organisms has a high proportion of “shredders” – the critters that that feed on CPOM and break it up into tinier bits called “fine particulate organic matter” or FPOM. In turn, organisms called “collectors” make use of the FPOM by filtering it from the water or accessing it in the sediments. [Allochthonous material can also include dissolved organic matter (DOM) carried into the stream by overland or subsurface flow.]

Schematic illustration of the River Continuum Concept, as modified from Vannote et al. (1980)

Schematic illustration of the River Continuum Concept, as modified from Vannote et al. (1980)

As you move downstream from the headwaters toward medium-sized rivers, the stream channel becomes wider and allochthonous input from overhanging forest and riparian vegetation decreases in abundance and importance relative to primary production (or autochthonous organic mattter) driven by available sunlight. In other words, algae and aquatic plants become the most important food producers. Organisms called “grazers” who scrape algae from surfaces become an important component of the aquatic food web, and grazers become less abundant.

Farther downstream, the ecosystem shifts again, as there is so much FPOM moving with the water and sediment, that collecters far outnumber either shredders or grazers. There’s still allochthonous input from the banks and being carried in by tributaries, and there’s still primary production occurring in the stream, but upstream “system inefficiency” or “leakage” in the processing of nutrients and organic material lets large river aquatic communities be based on material washing in from upstream.

The adjustment of river ecosystems in a downstream fashion that I’ve described above is part of the “river continuum concept”, described by Vannote and colleagues in 1980 in the Canadian Journal of Fisheries and Aquatic Science, and it is one of the unifying principles of modern stream ecology. At its root, the river continuum concept is driven by the relative proportion of allochthonous to autochthonous organic matter inputs to the stream.

While I’m not an ecologist, I was raised by one and I work with them, so when I hear the word allochthonous, I pictures leaves and logs in streams, rather than anything to do with rocks. So, I’ll end this post with some nice pictures of allochthonous material.

An overwhelming amount of allochthonous material in a headwater stream, Gaston County, North Carolina

An overwhelming amount of allochthonous material in a headwater stream, Gaston County, North Carolina. One of my MS students showed that debris jams like this were the biggest driver of groundwater-stream interactions, variations in sediment size, and changes in water chemistry in these tiny streams.

Allochthonous organic material in Clark Creek, Charlotte. High water has washed branches and leaves into the creek, where they got hung up on the riffle (or riprap).

Allochthonous organic material in Clark Creek, Charlotte. High water has washed branches and leaves into the creek, where they got hung up on the riffle (or riprap). What role do natural and artificial geomorphic structures (with their FPOM trapping abilities) play in promoting ecosystem health in urban streams? My colleagues and I are trying to find out.

Large wood jam on Mallard Creek, near Harrisburg, NC

Large wood jam on Mallard Creek, near Harrisburg, NC. For several years, I've taken my Fluvial Processes class to this spot, in part so that they can observe the geomorphic effects of wood in streams.

Wood in streams is utilitarian. During my PhD, I used stable large logs to cross streams and attach equipment.

I use large logs to cross streams and attach equipment. Here, in a spring-fed stream in Oregon, with extremely stable water levels and no floods, allochthonous material that falls into the stream stays where it falls and forms a substrate for a fabulous community of mosses and ferns.

Not a stream. Allochthonous input onto the surface of a lava flow, from the edge of a forest.

Not a stream. Here we are looking at allochthonous input onto the edge of a lava flow, from the forest beyond. On this young lava flow (in the Oregon Cascades), I found substantially greater soil depth near the edge of the flow, where organic acids from decaying allochthonous organic matter had probably sped up the weathering process, as well as contributing directly to the soil. In my PhD dissertation, one subsection had "allochthonous inputs" for a title.

Vannote, R., Minshall, G., Cummins, K., Sedell, J., & Cushing, C. (1980). The River Continuum Concept Canadian Journal of Fisheries and Aquatic Sciences, 37 (1), 130-137 DOI: 10.1139/f80-017

Posted by: Anne Jefferson | June 20, 2011

Anne is a “Strange Quark”

Wow! I won the “strange quark” (2nd place) award in a science writing contest, hosted by Three Quarks Daily, for blogging about the Mississippi River, floods, levees, and the illusion of control.

As I wrote in the comments at 3QD:

Wow! I never thought I’d actually win something for writing about stuff for fun. Thank you to Dr. Lisa Randall for selecting me, the folks at Three Quarks Daily for hosting this contest and boosting me into the finals. I am deeply honored to be a winner of the 3 Quarks Daily contest, and incredibly impressed by the company I’m in.

The 1993 Mississippi River floods were the event that made me become the scientist I am today, so I really wanted to do a creditable job explaining the perspectives and nuances of flood management. Based on the response to the piece, I must have done OK! But now I’ve set myself the goal of bringing that same quality of writing to more blog posts and my scientific papers, so I may be in trouble if they don’t live up to the high praise that this post has gotten.

Thanks to my readers for supporting me in the contest and in blogging generally. Special thanks to my co-blogger Chris for giving me a place to write and for encouraging and supporting me every day.

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