Scale-dependent lateral exchanges of organic carbon in a dryland river during a high-flow experiment

2016 ◽  
Vol 67 (9) ◽  
pp. 1293 ◽  
Author(s):  
Alistar I. Robertson ◽  
Adrienne Burns ◽  
Terry J. Hillman

We estimated the magnitude and direction of exchanges of particulate organic carbon (POC) and dissolved organic carbon (DOC) between the river and four floodplain wetlands (billabongs) and a 140-km reach of riverbank and floodplain of the Murrumbidgee River during a managed high-flow experiment. There was a net transport of organic carbon from the river to billabongs during connection, ranging from 87 to 525kg POC per billabong or from 1.4 to 5.7g POC m–2 of billabong sediment surface area and from 36 to 4357kg DOC, or from 0.4 to 29.8g DOC m–2. At the whole-reach scale, there was a net loss of 754Mg POC from the river channel to riverbank and floodplain and a net input of 821Mg DOC to the river channel. This DOC input, which was small relative to the total organic carbon in transit, was likely to have contributed significantly to oxidative processes in the river. The DOC entering the river was derived from litter and soils in riverbank habitats or from abraded biofilms in the river channel. The results support an extended flood-pulse concept that includes in-channel flow pulses as important elements in the biogeochemistry of dryland rivers. Piggybacking dam releases on tributary flows to deliver in-channel flows delivers significant benefit for riverine organic-matter cycles.

2002 ◽  
Vol 45 (11) ◽  
pp. 55-62 ◽  
Author(s):  
P.J. Whalen ◽  
L.A. Toth ◽  
J.W. Koebel ◽  
P.K. Strayer

Channelization of the Kissimmee River transformed a 167 km meandering river into a 9 metre deep, 75 metre wide, 90 km drainage canal (C-38) that is compartmentalized with levees and water control structures into a series of five stagnant pools. Channelization dramatically changed water level and flow characteristics, drained 21,000 hectares of floodplain wetlands and severely impacted fish and wildlife populations. A $500 million dollar restoration project will restore the ecological integrity of the river-floodplain system by reconstructing the natural river channel and reestablishing hydrologic processes. Sixty expectations have been established to quantify the ecosystem's recovery. The first phase of reconstruction was completed in February 2001 and included movement of 9.2 million cubic metres of earth to backfill 12 km of C-38, the explosive demolition of one water control structure, construction of two sections (2.4 km) of new river channel, and reestablishment of 24 contiguous km of river. Numerous social, political, and technical challenges have been encountered during the project's evolution. Recommendations are provided for future restoration projects.


2014 ◽  
Vol 64 ◽  
pp. 85-99 ◽  
Author(s):  
F.M. Keizer ◽  
P.P. Schot ◽  
T. Okruszko ◽  
J. Chormański ◽  
I. Kardel ◽  
...  

2014 ◽  
Vol 10 (2) ◽  
pp. 569-587 ◽  
Author(s):  
I. Pathirana ◽  
J. Knies ◽  
M. Felix ◽  
U. Mann

Abstract. There is generally a lack of knowledge on how marine organic carbon accumulation is linked to vertical export and primary productivity patterns in the Arctic Ocean. Despite the fact that annual primary production in the Arctic has increased as a consequence of shrinking sea ice, its effect on flux, preservation, and accumulation of organic carbon is still not well understood. In this study, a multi-proxy geochemical and organic-sedimentological approach is coupled with organic facies modelling, focusing on regional calculations of carbon cycling and carbon burial on the western Barents Shelf between northern Scandinavia and Svalbard. OF-Mod 3-D, an organic facies modelling software tool, is used to reconstruct and quantify the marine and terrestrial organic carbon fractions and to make inferences about marine primary productivity changes across the marginal ice zone (MIZ). By calibrating the model against an extensive set of sediment surface samples, we improve the Holocene organic carbon budget for ice-free and seasonally ice-covered areas in the western Barents Sea. The results show that higher organic carbon accumulation rates in the MIZ are best explained by enhanced surface water productivity compared to ice-free regions, implying that shrinking sea ice may reveal a significant effect on the overall organic carbon storage capacity of the western Barents Sea shelf.


1986 ◽  
Vol 25 (3) ◽  
pp. 293-311 ◽  
Author(s):  
Richard Hereford

Stream channels in the Paria River basin were eroded and partially refilled between 1883 and 1980. Basin-wide erosion began in 1883; channels were fully entrenched and widened by 1890. This erosion occurred during the well-documented period of arroyo cutting in the Southwest. Photographs of the Paria River channel taken between 1918 and 1940 show that the channel did not have a floodplain and remained wide and deep until the early 1940s. A thin bar (<50 cm), now reworked and locally preserved, was deposited at that time. Basin-wide aggradation, which began in the early 1940s, developed floodplains by vertical accretion. The floodplain alluvium, 1.3–3 m thick. consists of two units recognizable throughout the studied area. An older unit was deposited during a time of low flow and sediment yield whereas the younger unit was deposited during times of high flow, sediment yield, and precipitation. Tree-ring dating suggests that the older unit was deposited between the early 1940s and 1956, and the younger between 1956 and 1980. The units are not time transgressive, suggesting that deposition by knickpoint recession was not an important process. High peak-flood discharges were associated with crosion and low flood discharges with aggradation. The erosional or aggradational mode of the streams was determined principally by peak-flood discharge, which in turn was controlled by precipitation.


2004 ◽  
Vol 92 (5) ◽  
pp. 786-796 ◽  
Author(s):  
GER BOEDELTJE ◽  
JAN P. BAKKER ◽  
ALBERT TEN BRINKE ◽  
JAN M. VAN GROENENDAEL ◽  
MARTIN SOESBERGEN

2020 ◽  
Author(s):  
Lidija Globevnik ◽  
Sebastian Birk ◽  
Kathrin Januschke ◽  
Jochem Kail ◽  
Luka Snoj ◽  
...  

&lt;p&gt;The spatial reference framework is the lateral extent of the river channel and its floodplain, named &amp;#8220;flood-prone area extent&amp;#8221;. Due to human interventions into the hydrological cycle and morphological alterations of the river channel and its floodplain, some areas that were regularly flooded once, may not experience such flooding today. We characterize them as &amp;#8220;former floodplains&amp;#8221;. Floodplains flooded now are named &amp;#8220;active floodplains&amp;#8221;. The analysis is done on the spatial resolution level named &amp;#8220;Functional Elementary Catchment&amp;#8221; (FEC) of the European catchments and Rivers network system (Ecrins) database and for the flood-prone areas in Europe that include former and active floodplains with river channels. It is named &amp;#8220;Potential flood prone area&amp;#8221;. In the first step we defined floodplains typology. For the assessment part we developed indicators of floodplain forms and processes, defined their benchmark condition and performed quality classification. Here, we describe what spatial data we used and what data we still miss to produce reliable assessment. &amp;#160;&amp;#160;&lt;/p&gt;&lt;p&gt;The spatial layer &amp;#8220;Potential flood-prone area extent&amp;#8221; was derived from two spatial layers, Potential Riparian Zone Delineation of the Copernicus Land Monitoring Service and JRC flood hazard map for Europe 100-year return period, a result of flood model &amp;#8220;LisFlood&amp;#8221;. &amp;#160;&lt;/p&gt;&lt;p&gt;The candidate list of typology factors included 31 factors derived from various databases such are Ecrins, MARS, FAO, Copernicus, WorldClim, PCGLOBEWB and IHME. Factors represent abiotic state before human intervention into rivers and floodplains and are grouped into regions, climate, morphology, hydrology, geology and &amp;#160;physics &amp;#8211; river dynamics. The calculated factors are reasonably covering the assessment area (95% - 99%) with the exception of the physics &amp;#8211; river dynamics factors. This information was obtained for less than 30% of European area. The selection of factors defining floodplain types was based on the criterion of adequate spatial coverage, reliability and non-redundancy. As a result, floodplain types were derived from seven factors, three morphological (river average altitude and slope and average floodplain width), one geological (dominant catchment geo-chemistry) and three hydrological factors (specific runoff as mean annual discharge divided by catchment area, high flow duration and high flow pulses). Hydrological and morphological factors are only approximations to the natural state, so we propose to further develop databases providing information on river and floodplain hydromorphology prior to major human interventions.&lt;/p&gt;&lt;p&gt;Indicators of floodplain forms are derived from two layers, Riparian Zone Land Cover/Land Use and High Resolution Water &amp; Wetness of the Copernicus Land Monitoring Service. The land use layer provides a good basis for assessing the current distribution of floodplain habitats. We also estimate the size of the active natural floodplains using wetness data, but the results can be improved with systematic European wide information on present hydrotechnical structures and hydromorphological alterations. Such data would also support assessment of floodplain ecological condition and management options. &amp;#160;&lt;/p&gt;


2015 ◽  
Vol 75 (3 suppl 1) ◽  
pp. 190-204 ◽  
Author(s):  
TM. Sanaiotti ◽  
TG. Junqueira ◽  
V. Palhares ◽  
FH. Aguiar-Silva ◽  
LMP. Henriques ◽  
...  

Abstract In the Brazilian Amazon, two monospecific genera, the Harpy Eagle and Crested Eagle have low densities and are classified by IUCN as Near Threatened due to habitat loss, deforestation, habitat degradation and hunting. In this study, we evaluate occurrence of these large raptors using the environmental surveys database from Belo Monte Hydroelectric Power Plant. Integrating the dataset from two methods, we plotted a distribution map along the Xingu River, including records over a 276-km stretch of river. Terrestrial surveys (RAPELD method) were more efficient for detecting large raptors than standardized aquatic surveys, although the latter were complementary in areas without modules. About 53% of the records were obtained during activities of wildlife rescue/flushing, vegetation suppression or in transit. Between 2012 and 2014, four Harpy Eagles were removed from the wild; two shooting victims, one injured by collision with power lines and one hit by a vehicle. Also, seven nests were mapped. The mean distance between Harpy Eagle records was 15 km along the river channel, with a mean of 20 km between nests near the channel, which allowed us to estimate 20 possible pairs using the alluvial forest, riverine forest and forest fragments. Territories of another ten pairs will probably be affected by inundation of the Volta Grande channel, which is far from the main river. The average distance between Crested Eagle records was 16 km along the river channel. The only nest found was 1.3 km away from a Harpy Eagle nest. The remnant forests are under threat of being replaced by cattle pastures, so we recommend that permanently protected riparian vegetation borders (APP) be guaranteed, and that forest fragments within 5 km of the river be conserved to maintain eagle populations.


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