Members of the Sediment Dynamics Group recently returned from a three-week stint in Brazil, where we completed fieldwork on the Amazon River and its associated sedimentary environments.
Our first field site was along the Amapá coastline north of the mouth of the Amazon River. The mangroves that flank the coast here are bathed in Amazon River sediment that is transported northward after exiting the mouth. We undertook a pilot study along the Rio Calçoene, downstream of the town of Calçoene.
Near Calçoene, the river has relatively little suspended sediment, and the water appears quite clear.
Rio Calcoene near Calcoene
Closer to the mouth, suspended sediment concentrations are much higher, and the river starts to resemble chocolate milk. Almost all of this sediment is likely from the Amazon River, the mouth of which is some 250 km to the south.
Near the mouth of the Rio Calcoene
In addition to making measurements and collecting samples along the river itself, we did work in a few small channels that incise the mangrove forests that characterize this part of the Brazilian coastline.
A small channel at low tide incising mangrove forest
The UW’s R/V Clifford A. Barnes recently completed its 1000th research cruise, as described in this UW Today article. Our group has used the Barnes extensively over the past few years as part of our project on sediment impacts related to the Elwha dam removal. Be sure to check the photo gallery on the UW Today article for a shot of our own Kristen Webster on a Barnes cruise in 2009!
Wow–what a whirlwind. The second half of our fieldwork was a frenzy of activity. We finished the second 25-hour transect and completed the third quickly and efficiently. With over 75 hours of continuous ADCP measurements (3, 25-hour station occupations), 230-plus CTD (conductivity-temperature-depth) casts, over 100 sediment samples, and about 150 water samples, we have a lot of data on our hands waiting to be analyzed. Right now we’re in Seoul airport waiting for our flight back to Seattle. Look for another post or two with some more great photos and perhaps a few data plots describing what exactly it is we did on the river. For now, we’re headed to our gate, so here a few photos.
A night view from the bow of Aaron filtering
Rip doing creating a manual vacuum while we repaired our vacuum pump
On April 12–16 we went on our 5th survey cruise to the Elwha Delta as part of an ongoing 2-year field effort. The cruise served a dual purpose as an educational field experience for the seven students in the spring Marine Sedimentary Processes class. Students helped collect data for the ongoing Elwha sediment dispersal project, and also collected special data for their individual research projects. The weather was pretty rough for the first couple days, but we were rewarded with sunshine toward the end of the trip. In all, we collected 72 sediment samples, dozens of water samples, ship-based ADCP data, PAR sensor (light) data in the plume, seabed videos, benthos samples, CTD transects, and more. Everyone had a great time and learned a lot!
On April 13th, we re-deployed the primary tripod for the fifth time since November 2011. We’ll see it again later this summer (hopefully after the dams are completely gone).
Andrea and Trevor prepare to collect a surface water sample with a Niskin bottle.
Ben and Tianna collect water samples.
Riane collects light measurements from 1 m, 2 m, 5 m, and 10 m water depths in the surface plume.
MUD! (and sand) Finally seeing noticeable amounts of mud mixed with sand near the river mouth.
We’re just past half way through our second 25-hour transect, this one about 15 km farther upstream from our first transect location. Things have been going well overall, though the hours are long and the weather decidedly un-Seattle-like with temperatures in the mid-to-upper 90s. We’ll finish this transect around 9 pm tonight and then everyone will get some well deserved rest before starting our third and final transect bright and early tomorrow morning.
Loading up with more water for the showers and toilets
Yesterday we spent our first day on the river, loading gear, testing equipment and getting settled in to our home and work space for the next few days. From Dai Ngai we transited along Cu Lao Dung island on our way to our first 25-hour transect location near the mouth of the Mekong. We started the transect at 5 am today and are about 13 hours in at the time of this writing. The kinks have mostly been worked out and the science team and boat crew are getting in to a good groove.
We’ll finish the transect around 6 am tomorrow and then a few folks will explore some mangrove areas for potential future work. Then we’ll have some much-needed down time and transit to our next transect location farther up river.
Aaron and Dan setting up the ADCP.
So far the data we have collected look promising. Check back for some preliminary results in the coming days.
Aaron, Dan, and Rip reflected on a stanchion on board the VLC.
Today we made the 3.5 hour journey from Saigon to Can Tho, where we met colleagues from Can Tho University. From there we headed to Dai Ngai where we met the vessel we’ll be using for research: the Vinh Long Cruiser.
Vinh Long Cruiser
The Cruiser is very much a vessel of opportunity but it should work out well for the types of work we’ll be doing over the coming week. Tomorrow morning we’ll load up and start setting up equipment. For now it’s dinner time, a much-needed shower, and our last night of sleep on dry land for a while.
We spent most of today purchasing more supplies and testing equipment in preparation for traveling to the Mekong tomorrow. Our route will take us through Can Tho where we will meet up with colleagues from Can Tho University. Then we will spend the night in Soc Trang before meeting the boat on Tuesday morning.
Check out a few photos from today in the gallery below.
Sunrise over the Saigon River
Rip and Aaron purchasing hardware and tools
Testing the ADCP in the hotel room
Visit from the fire department at the hotel this morning
Because we packed our gear within the confines of airline luggage, we are assembling here in Vietnam some of the larger equipment needed for our field work. The video below shows stainless steel pipe being cut at a storefront in Saigon’s District 11, which is also Chinatown. We will bolt the pipe to a flanged mounting bracket (that was small enough to fit in luggage) built by UW Oceanography engineering services. Fully assembled, this mount will support our ADCP–acoustic Doppler current profiler–which measures water velocity from a moving boat and which we will use extensively on the Mekong River in the coming days.
Several members of the Sediment Dynamics Group left Seattle yesterday for Vietnam where we will be doing field research on the Mekong River for the next two weeks or so.
On our last expedition we shipped pallets of gear by air freight to Saigon (Ho Chi Minh City) but this trip will be shorter and leaner with only what we can transport as air baggage.
This photo shows what three grad students’ worth of gear looks like before heading to the airport. The fourth member of the US team will arrive about 24 hours after we do with more gear (hopefully!).
Our group made it safely to Seoul, South Korea with a tight connection and arrived in Saigon about an hour ago. We’ll meet up with Vietnamese and US colleagues and prepare for about a week of work on the tidal portion of the Mekong. Look for more updates in the coming days!