Dissolved organic carbon mobilisation in relation to variable discharges and environmental flows in a highly regulated lowland river

2012 ◽  
Vol 63 (12) ◽  
pp. 1218 ◽  
Author(s):  
Douglas P. Westhorpe ◽  
Simon M. Mitrovic
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Environmental Flows ◽  
Environmental Flow ◽  
Lowland River ◽  
Rainfall Runoff ◽  
Management Scenarios ◽  
High Discharge ◽  
Linear Relationships ◽  
Floodplain Inundation

The relationships between discharge and dissolved organic carbon (DOC) have been extensively studied in rainfall runoff-driven stream systems. Less is known about discharge and DOC relationships in river systems dependent on floodplain inundation. We examined DOC dynamics and mobilisation over low discharge periods and several larger discharge events in the highly regulated lowland Namoi River, Australia. Stable isotope signatures (δ13C) of various water-column fractions (e.g. 200 µm, fine particulate organic matter) were used to determine the sources of DOC. DOC concentrations over low discharge periods were fairly similar among sites and ranged between 5 and 10 mg L–1. Concentrations during a high-discharge event increased substantially with a mean of 20.4 mg L–1 and a maximum of 44 mg L–1. Significant positive linear relationships were found between DOC concentrations and discharge (P < 0.001, r2 = 0.45). The 13C composition of DOC sampled across the three sites (e.g. –26.2‰) suggests a mixture of terrestrial and aquatic sources, with little downstream variation; however, we would envisage that during periods of high discharge allochthonous sources would dominate. Environmental flows (that are ecologically beneficial, potentially reversing changes brought about by flow regulation) have been allocated to the river, with the intention to increase the amount of DOC delivered to the river. The relationship between DOC and discharge was used to estimate DOC loads to the river under different modelled flow-management scenarios, including without environmental flow, with environmental flow, and simulated natural (low development) flow. On the basis of the modelling results, environmental flows should increase the amount of allochthonous DOC transported within the river in years with moderate and large flow events. Years with low flows did not deliver large loads of allochthonous DOC. The present results showed the potential variability in DOC delivery in relation to floodplain inundation in a lowland river that may not otherwise be detected in rainfall/runoff-driven headwater streams.

scholarly journals Uncertainties in dissolved organic carbon load estimation in a small stream

2013 ◽  
Vol 61 (1) ◽  
pp. 81-83 ◽  
Author(s):  
Olaf Büttner ◽  
Jörg Tittel
Keyword(s):  
Organic Carbon ◽  
Absorption Coefficient ◽  
Dissolved Organic Carbon ◽  
Additional Data ◽  
Sampling Frequency ◽  
Carbon Pools ◽  
Load Estimation ◽  
Small Stream ◽  
High Discharge ◽  
Carbon Load

Abstract Dissolved organic carbon (DOC) transported by rivers represents an important link between carbon pools of terrestrial and oceanic ecosystems. However, it is unclear how frequent DOC must be sampled to obtain reasonable load estimates. Here, we used continuous records of the specific UV absorption coefficient (SAC) and discharge from a headwater stream at the Ore Mountains (Germany) to calculate load errors depending on DOC sampling frequency. SAC was used as a proxy for DOC. The results show that the load was underestimated by 13-19% with monthly, 10-13% with bi-weekly and 7-9% with weekly DOC samplings, respectively. We conclude that collecting additional data from high discharge events decrease the error significantly.

scholarly journals Rapid accretion of dissolved organic carbon in the springs of Florida: the most organic-poor natural waters

2010 ◽  
Vol 7 (12) ◽  
pp. 4051-4057 ◽  
Author(s):  
C. M. Duarte ◽  
Y. T. Prairie ◽  
T. K. Frazer ◽  
M. V. Hoyer ◽  
S. K. Notestein ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Production ◽  
Natural Waters ◽  
Gross Primary Production ◽  
Spring Discharge ◽  
High Discharge ◽  
Discharge Rates ◽  
Receiving Waters ◽  
Flowing Waters

Abstract. The concentration of dissolved organic carbon (DOC) in groundwater emanating as spring discharge at several locations in Florida, USA and the net increase in DOC in the downstream receiving waters were measured as part of a larger investigation of carbon dynamics in flowing waters. Springs with high discharge (>2.8 m3 s−1) were found to be the most organic-poor natural waters yet reported (13 ± 1.6 μmol C L−1), while springs with lesser discharge exhibited somewhat higher DOC concentrations (values ranging from 30 to 77 μmol C L−1). DOC concentrations increased rapidly downstream from the point of spring discharge, with the calculated net areal input rate of DOC ranging from 0.04 to 1.64 mol C m−2 d−1 across springs. Rates of DOC increase were generally greater in those springs with high discharge rates. These input rates compare favorably with values reported for gross primary production in these macrophyte-dominated spring systems, assuming that 17% of macrophyte primary production is lost, on average, as DOC. The measures reported here are possible only because of the remarkably low DOC levels in the up-surging groundwaters and the short residency times of the water in the spring-runs themselves.

scholarly journals Rapid accretion of dissolved organic carbon in the Springs of Florida: the most organic-poor natural waters

2010 ◽  
Vol 7 (4) ◽  
pp. 5253-5267
Author(s):  
C. M. Duarte ◽  
R. Martínez ◽  
Y. T. Prairie ◽  
T. K. Frazer ◽  
M. V. Hoyer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Primary Production ◽  
Natural Waters ◽  
Gross Primary Production ◽  
Spring Discharge ◽  
High Discharge ◽  
Discharge Rates ◽  
Receiving Waters ◽  
Flowing Waters

Abstract. The concentration of dissolved organic carbon (DOC) in groundwater emanating as spring discharge at several locations in Florida, USA, and the net rate of DOC increase in the downstream receiving waters were measured as part of a larger investigation of carbon dynamics in flowing waters. Springs with high discharge (>2.8 m3 s−1) were found to be the most organic-poor natural waters yet reported (13 ±1.6 μmol C L−1), while springs with lesser discharge exhibited somewhat higher DOC concentrations (values ranging from 30 to 77 μmol C L−1). DOC concentrations increased rapidly downstream from the point of spring discharge, with the calculated net areal input rate of DOC ranging from 0.04 to 1.64 mol C m−2 d−1 across springs. Rates of DOC increase were generally greater in those springs with high discharge rates. These input rates compare favorably with values reported for gross primary production in these macrophyte-dominated spring systems, assuming that 17% of macrophyte primary production is lost, on average, as DOC. The measures reported here are possible only because of the remarkably low DOC levels in the up-surging groundwaters and the short residency times of the water in the spring-runs themselves.

scholarly journals Hydrological controls on DOC : nitrate resource stoichiometry in a lowland, agricultural catchment, southern UK

2017 ◽  
Author(s):  
Catherine M. Heppell ◽  
Andrew Binley ◽  
Mark Trimmer ◽  
Tegan Darch ◽  
Ashley Jones ◽  
...  
Keyword(s):  
Climate Change ◽  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River Water ◽  
Positive Relationship ◽  
Agricultural Landscapes ◽  
Lowland River ◽  
Significant Positive Relationship ◽  
Molar Ratios ◽  
The Relationship

Abstract. The role that hydrology plays in governing the interactions between dissolved organic carbon (DOC) and nitrogen in rivers draining lowland, agricultural landscapes is currently poorly understood, yet important to assess given the potential changes to production and delivery of DOC and nitrate arising from climate change. We measured DOC and nitrate concentrations in river water of six reaches of the lowland River Hampshire Avon (Wiltshire, southern UK) in order to quantify the relationship between Baseflow Index (BFI) and DOC : nitrate molar ratios across contrasting geologies (Chalk, Greensand and clay). We found a significant positive relationship between nitrate and Baseflow Index (p 

scholarly journals Temperature controls production but hydrology regulates export of dissolved organic carbon at the catchment scale

2020 ◽  
Vol 24 (2) ◽  
pp. 945-966 ◽  
Author(s):  
Hang Wen ◽  
Julia Perdrial ◽  
Benjamin W. Abbott ◽  
Susana Bernal ◽  
Rémi Dupas ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Groundwater Flow ◽  
Soil Water ◽  
Reactive Transport ◽  
Stream Water ◽  
Catchment Scale ◽  
High Discharge ◽  
Doc Production ◽  
Doc Concentration

Abstract. Lateral carbon flux through river networks is an important and poorly understood component of the global carbon budget. This work investigates how temperature and hydrology control the production and export of dissolved organic carbon (DOC) in the Susquehanna Shale Hills Critical Zone Observatory in Pennsylvania, USA. Using field measurements of daily stream discharge, evapotranspiration, and stream DOC concentration, we calibrated the catchment-scale biogeochemical reactive transport model BioRT-Flux-PIHM (Biogeochemical Reactive Transport–Flux–Penn State Integrated Hydrologic Model, BFP), which met the satisfactory standard of a Nash–Sutcliffe efficiency (NSE) value greater than 0.5. We used the calibrated model to estimate and compare the daily DOC production rates (Rp; the sum of the local DOC production rates in individual grid cells) and export rate (Re; the product of the concentration and discharge at the stream outlet, or load). Results showed that daily Rp varied by less than an order of magnitude, primarily depending on seasonal temperature. In contrast, daily Re varied by more than 3 orders of magnitude and was strongly associated with variation in discharge and hydrological connectivity. In summer, high temperature and evapotranspiration dried and disconnected hillslopes from the stream, driving Rp to its maximum but Re to its minimum. During this period, the stream only exported DOC from the organic-poor groundwater and from organic-rich soil water in the swales bordering the stream. The DOC produced accumulated in hillslopes and was later flushed out during the wet and cold period (winter and spring) when Re peaked as the stream reconnected with uphill and Rp reached its minimum. The model reproduced the observed concentration–discharge (C–Q) relationship characterized by an unusual flushing–dilution pattern with maximum concentrations at intermediate discharge, indicating three end-members of source waters. A sensitivity analysis indicated that this nonlinearity was caused by shifts in the relative contribution of different source waters to the stream under different flow conditions. At low discharge, stream water reflected the chemistry of organic-poor groundwater; at intermediate discharge, stream water was dominated by the organic-rich soil water from swales; at high discharge, the stream reflected uphill soil water with an intermediate DOC concentration. This pattern persisted regardless of the DOC production rate as long as the contribution of deeper groundwater flow remained low (<18 % of the streamflow). When groundwater flow increased above 18 %, comparable amounts of groundwater and swale soil water mixed in the stream and masked the high DOC concentration from swales. In that case, the C–Q patterns switched to a flushing-only pattern with increasing DOC concentration at high discharge. These results depict a conceptual model that the catchment serves as a producer and storage reservoir for DOC under hot and dry conditions and transitions into a DOC exporter under wet and cold conditions. This study also illustrates how different controls on DOC production and export – temperature and hydrological flow paths, respectively – can create temporal asynchrony at the catchment scale. Future warming and increasing hydrological extremes could accentuate this asynchrony, with DOC production occurring primarily during dry periods and lateral export of DOC dominating in major storm events.

scholarly journals Diel variation of dissolved organic carbon during large flow events in a lowland river

Limnologica ◽  
2012 ◽  
Vol 42 (3) ◽  
pp. 220-226 ◽  
Author(s):  
Douglas P. Westhorpe ◽  
Simon M. Mitrovic ◽  
K. Benjamin Woodward
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Diel Variation ◽  
Lowland River ◽  
Large Flow

Carbon and nutrient subsidies to a lowland river following floodplain inundation

2016 ◽  
Vol 67 (9) ◽  
pp. 1302 ◽  
Author(s):  
Daryl L. Nielsen ◽  
Robert A. Cook ◽  
Nathan Ning ◽  
Ben Gawne ◽  
Rochelle Petrie
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
River Channel ◽  
Resource Subsidies ◽  
Lowland Rivers ◽  
Main River ◽  
Main River Channel ◽  
Eastern Australia ◽  
Floodplain Inundation ◽  
Nutrient Subsidies

Despite the perceived importance of floodplain inundation to the functioning of lowland rivers, there is limited understanding of the contribution that floodplains make to the main river channel during floods. In 2010, substantial flooding occurred throughout south-eastern Australia, which provided an opportunity to quantify the export of biological material and nutrients from a floodplain back in to the main river channel. We quantified the amounts of zooplankton, phytoplankton, dissolved organic carbon and nutrients within the main river channel of the River Murray immediately upstream of the Barmah–Millewa Forest, and at two sites immediately downstream of the forest during two flood events in July and October of 2010. Results demonstrated that although a smaller flood event in July did not contribute substantially to an increase in the measured parameters, a much larger flood in October contributed 0.4 tonnes (t) of phytoplankton; 7t of zooplankton and 300t of dissolved organic carbon. This suggests that small floods will provide minimal resource subsidies back into the main channel after the cessation of flooding. In comparison, larger floods that result in large volumes of floodplain water returning to the river will provide substantial subsidies of terrestrially derived resources.

Changes in dissolved organic carbon concentration in renaturalized lowland river

2008 ◽  
Vol 3 (-1) ◽  
Author(s):  
Piotr Zieliński ◽  
Elżbieta Jekatierynczuk-Rudczyk ◽  
Andrzej Górniak
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Carbon Concentration ◽  
Lowland River ◽  
Organic Carbon Concentration

scholarly journals Can the heterogeneity in stream dissolved organic carbon be explained by contributing landscape elements?

2013 ◽  
Vol 10 (10) ◽  
pp. 15913-15949 ◽  
Author(s):  
A. M. Ågren ◽  
I. Buffam ◽  
D. M. Cooper ◽  
T. Tiwari ◽  
C. D. Evans ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Model Development ◽  
Field Measurements ◽  
Mixing Model ◽  
Residual Analysis ◽  
Base Flow ◽  
Stream Network ◽  
Landscape Elements ◽  
High Discharge

Abstract. The controls on stream dissolved organic carbon (DOC) concentrations were investigated in a 68 km2 catchment by applying a landscape-mixing model to test if downstream concentrations could be predicted from contributing landscape elements. The landscape-mixing model reproduced the DOC concentration well throughout the stream network during times of high discharge, but was even more useful for providing a baseline for residual analysis, which highlighted areas for further conceptual model development. The landscape-mixing model approach is conceptually simple and easy to apply, requiring relatively few field measurements and minimal parameterization. The residual analysis highlighted areas of the stream network that were not well represented by simple mixing of headwaters, as well as flow conditions during which simple mixing based on headwater watershed characteristics did not apply. Specifically, we found that during periods of base flow the larger valley streams underlain by fine sorted sediments had much lower DOC concentrations than would be predicted by simple mixing; while peatland streams had higher DOC than predicted. During periods of intermediate and high flow the model made more accurate predictions of downstream DOC. Our interpretation is that the higher degree of hydrological connectivity during high flows, possibly combined with shorter stream residence times, increased the predictive power of this whole-watershed based mixing model. However, there was still a clear pattern during high discharge periods, with peatland streams having lower DOC than would be predicted by simple mixing while forested streams had higher DOC. These observations suggest several potential mechanisms to be further explored using more focused field and process-based modeling studies, especially on the role of changing hydrological pathways.

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