scholarly journals Diel fluctuations of viscosity-driven riparian inflow affect streamflow DOC concentration

2018 ◽  
Vol 15 (7) ◽  
pp. 2177-2188 ◽  
Author(s):  
Michael P. Schwab ◽  
Julian Klaus ◽  
Laurent Pfister ◽  
Markus Weiler
Keyword(s):  
High Frequency ◽  
Riparian Zone ◽  
Stream Water ◽  
Rainfall Runoff ◽  
Lower Viscosity ◽  
Doc Concentration ◽  
Diel Fluctuations ◽  
Runoff Events ◽  
Headwater Catchment

Abstract. Diel fluctuations of stream water DOC concentrations are generally explained by a complex interplay of different instream processes. We measured the light absorption spectrum of water and DOC concentrations in situ and with high frequency by means of a UV–Vis spectrometer during 18 months at the outlet of a forested headwater catchment in Luxembourg (0.45 km2). We generally observed diel DOC fluctuations with a maximum in the afternoon during days that were not affected by rainfall–runoff events. We identified an increased inflow of terrestrial DOC to the stream in the afternoon, causing the DOC maxima in the stream. The terrestrial origin of the DOC was derived from the SUVA-254 (specific UV absorbance at 254 nm) index, which is a good indicator for the aromaticity of DOC. In the studied catchment, the most likely process that can explain the diel DOC input variations towards the stream is the so-called viscosity effect. The water temperature in the upper parts of the saturated riparian zone is increasing during the day, leading to a lower viscosity and therefore a higher hydraulic conductivity. Consequently, more water from areas that are rich in terrestrial DOC passes through the saturated riparian zone and contributes to streamflow in the afternoon. We believe that not only diel instream processes, but also viscosity-driven diel fluctuations of terrestrial DOC input should be considered to explain diel DOC patterns in streams.

scholarly journals Diel fluctuations of viscosity-driven riparian inflow affect streamflow DOC concentration

2017 ◽  
Author(s):  
Michael P. Schwab ◽  
Julian Klaus ◽  
Laurent Pfister ◽  
Markus Weiler
Keyword(s):  
High Frequency ◽  
Riparian Zone ◽  
Rainfall Runoff ◽  
Complex Interplay ◽  
Lower Viscosity ◽  
Doc Concentration ◽  
Diel Fluctuations ◽  
Runoff Events ◽  
Headwater Catchment

Abstract. Diel fluctuations of streamwater DOC concentrations are generally explained by a complex interplay of different instream processes. We measured the light absorption spectrum of water and DOC concentrations in-situ and with high-frequency by means of a UV-Vis spectrometer during 18 months at the outlet of a forested headwater catchment in Luxembourg (0.45 km2). We generally observed diel DOC fluctuations with a maximum in the afternoon during days that were not affected by rainfall-runoff events. We identified an increased inflow of terrestrial DOC to the stream in the afternoon, causing the DOC maxima in the stream. The terrestrial origin of the DOC was derived from the SUVA-254 (specific UV absorbance at 254 nm) index, which is a good indicator for the aromaticity of DOC. In the studied catchment, the only possible process that can explain the diel DOC input variations towards the stream is the so-called viscosity effect. The water temperature in the upper parts of the riparian zone is increasing during the day, leading to a lower viscosity and therefore a higher hydraulic conductivity. Consequently, more water from areas that are rich in terrestrial DOC passes through the riparian zone and contributes to streamflow in the afternoon. We believe that not only diel instream processes, but also viscosity driven diel fluctuations of terrestrial DOC input should be considered for explaining diel DOC patterns in streams.

scholarly journals High-frequency measurements explain quantity and quality of dissolved organic carbon mobilization in a headwater catchment

2019 ◽  
Vol 16 (22) ◽  
pp. 4497-4516 ◽  
Author(s):  
Benedikt J. Werner ◽  
Andreas Musolff ◽  
Oliver J. Lechtenfeld ◽  
Gerrit H. de Rooij ◽  
Marieke R. Oosterwoud ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
High Frequency ◽  
Riparian Zone ◽  
Quality Parameters ◽  
Riparian Zones ◽  
Frequency Measurements ◽  
Seasonal Scale ◽  
Headwater Catchment

Abstract. Increasing dissolved organic carbon (DOC) concentrations and exports from headwater catchments impact the quality of downstream waters and pose challenges to water supply. The importance of riparian zones for DOC export from catchments in humid, temperate climates has generally been acknowledged, but the hydrological controls and biogeochemical factors that govern mobilization of DOC from riparian zones remain elusive. A high-frequency dataset (15 min resolution for over 1 year) from a headwater catchment in the Harz Mountains (Germany) was analyzed for dominant patterns in DOC concentration (CDOC) and optical DOC quality parameters SUVA254 and S275−295 (spectral slope between 275 and 295 nm) on event and seasonal scales. Quality parameters and CDOC systematically changed with increasing fractions of high-frequency quick flow (Qhf) and antecedent hydroclimatic conditions, defined by the following metrics: aridity index (AI60) of the preceding 60 d and the quotient of mean temperature (T30) and mean discharge (Q30) of the preceding 30 d, which we refer to as discharge-normalized temperature (DNT30). Selected statistical multiple linear regression models for the complete time series (R2=0.72, 0.64 and 0.65 for CDOC, SUVA254 and S275−295, resp.) captured DOC dynamics based on event (Qhf and baseflow) and seasonal-scale predictors (AI60, DNT30). The relative importance of seasonal-scale predictors allowed for the separation of three hydroclimatic states (warm and dry, cold and wet, and intermediate). The specific DOC quality for each state indicates a shift in the activated source zones and highlights the importance of antecedent conditions and their impact on DOC accumulation and mobilization in the riparian zone. The warm and dry state results in high DOC concentrations during events and low concentrations between events and thus can be seen as mobilization limited, whereas the cold and wet state results in low concentration between and during events due to limited DOC accumulation in the riparian zone. The study demonstrates the considerable value of continuous high-frequency measurements of DOC quality and quantity and its (hydroclimatic) key controlling variables in quantitatively unraveling DOC mobilization in the riparian zone. These variables can be linked to DOC source activation by discharge events and the more seasonal control of DOC production in riparian soils.

scholarly journals Analysis of the Mixing Processes in a Shallow Subtropical Reservoir and Their Effects on Dissolved Organic Matter

Water ◽  
2019 ◽  
Vol 11 (4) ◽  
pp. 737 ◽  
Author(s):  
Wang ◽  
Zhang ◽  
Bertone ◽  
Stewart ◽  
O’Halloran
Keyword(s):  
High Frequency ◽  
Field Measurements ◽  
Vital Role ◽  
Wet Season ◽  
Mixing Processes ◽  
Reservoir Water ◽  
Doc Concentration ◽  
1D Model ◽  
Transport And Mixing

A good understanding of the physical processes of lakes or reservoirs, especially of those providing drinking water to residents, plays a vital role in water management. In this study, the water circulation and mixing processes occurring in the shallow, subtropical Tingalpa Reservoir in Australia have been investigated. Bathymetrical, meteorological, chemical and physical data collected from field measurements, laboratory analysis of water sampling and an in-situ Vertical Profile System (VPS) were analysed. Based on the high-frequency VPS dataset, a 1D model was developed to provide information for vertical transport and mixing processes. The results show that persistent high air temperature and stable reservoir water depth lead to a prolonged thermal stratification. Analysis indicates that heavy rainfalls have a significant impact on water quality when the dam level is low. The peak value of Dissolved Organic Carbon (DOC) concentration occurred in the wet season, while the specific UV absorbance (SUVA) value decreased when solar radiation increased from spring to summer. The study aims to provide a comprehensive approach for understanding and modelling the water mixing processes in similar lakes with high-frequency data from VPS’s or other monitoring systems.

How do concentration-discharge relations vary among rainfall-runoff events? An analysis for the Ressi experimental catchment (Italian pre-Alps)

2021 ◽  
Author(s):  
Giulia Zuecco ◽  
Chiara Marchina ◽  
Ylenia Gelmini ◽  
Anam Amin ◽  
Ilja van Meerveld ◽  
...  
Keyword(s):  
Electrical Conductivity ◽  
Stable Isotopes ◽  
Temporal Dynamics ◽  
Major Ions ◽  
Stream Water ◽  
High Temporal Resolution ◽  
Runoff Coefficient ◽  
Rainfall Runoff ◽  
Antecedent Soil Moisture ◽  
Runoff Events

<p>Understanding discharge and solute responses is pivotal for water resources management and pollution mitigation measures. The few studies that have analysed concentration-discharge relations using high temporal resolution tracer data collected during rainfall-runoff events have shown that these relations may vary for different events and depend on season, event characteristics or antecedent wetness conditions. </p><p>In this study, we used hydrometric and tracer data (stable isotopes, major ions and electrical conductivity (EC)) to i) compare the concentration-discharge relations for different tracers, ii) characterize the hysteretic relations between discharge and tracer concentrations at the event timescale, and iii) determine whether the changes in hysteresis can be explained by event characteristics.</p><p>Data collection was carried out in the Ressi catchment, a 2-ha forested watershed in the Italian pre-Alps. The catchment is characterized by high seasonality in runoff response, due to the seasonality in rainfall (high in fall) and evapotranspiration (high in summer). Discharge and rainfall have been measured continuously since August 2012. Stream water, precipitation, shallow groundwater and soil water samples were collected for tracer analyses during 20 rainfall-runoff events between September 2015 and August 2018. All samples were analyzed for EC, isotopic composition (<sup>2</sup>H and <sup>18</sup>O) and major ion concentrations. To investigate the possible controls on concentration-discharge relations, we determined the main characteristics (e.g., total event rainfall, rainfall intensities, antecedent soil moisture and depth to water table, runoff coefficient) for each selected rainfall-runoff event.</p><p>The EC, calcium, magnesium, sodium and sulfate concentrations in stream water decreased during rainfall events, due to the dilution by rain water. The concentration-discharge relations for these tracers with a dilution behavior were stronger and more significant than for the tracers that were mobilized during the event. Interestingly, nitrate, potassium and chloride, concentrations sometimes increased at the onset of events, likely due to a rapid flushing of solutes from the dry parts of the stream channel and the riparian area, and then decreased during the event. These temporal dynamics in solute concentrations resulted in different hysteretic relations with discharge. Clockwise loops (i.e., discharge peaked later than the tracer concentrations) were common for the isotopes, chloride and potassium, whereas anti-clockwise hysteresis loops were more typical for EC, magnesium, calcium, sulfate, sodium and nitrate. A preliminary correlation analysis suggests that event characteristics alone cannot explain the changes in hysteresis, except for the hysteresis area for the relations between discharge and calcium concentration that depends on the magnitude of the rainfall event (i.e., the larger the rainfall amount and the runoff coefficient, the smaller the hysteresis loop). </p><p>These results highlight the importance of the first flush and indicate that runoff processes and solute sources can change when the catchment becomes wetter and connectivity of the hillslopes to the stream increases.</p><p> </p><p>Keywords: concentration-discharge relation; major ions; electrical conductivity; stable isotopes; hysteresis; forested catchment.</p>

scholarly journals Carbon dioxide transport across the hillslope–riparian–stream continuum in a boreal headwater catchment

2015 ◽  
Vol 12 (6) ◽  
pp. 1881-1892 ◽  
Author(s):  
F. I. Leith ◽  
K. J. Dinsmore ◽  
M. B. Wallin ◽  
M. F. Billett ◽  
K. V. Heal ◽  
...  
Keyword(s):  
Riparian Zone ◽  
Headwater Streams ◽  
Stream Water ◽  
Storm Events ◽  
Carbon Export ◽  
Carbon Dioxide Transport ◽  
Stream Surface ◽  
Co2 Concentrations ◽  
Daily Water ◽  
Headwater Catchment

Abstract. Headwater streams export CO2 as lateral downstream export and vertical evasion from the stream surface. CO2 in boreal headwater streams generally originates from adjacent terrestrial areas, so determining the sources and rate of CO2 transport along the hillslope–riparian–stream continuum could improve estimates of CO2 export via the aquatic pathway, especially by quantifying evasion at higher temporal resolutions. Continuous measurements of dissolved CO2 concentrations and water table were made along the hillslope–riparian–stream continuum in the Västrabäcken sub-catchment of the Krycklan catchment, Sweden. Daily water and CO2 export from the hillslope and riparian zone were estimated over one hydrological year (October 2012–September 2013) using a flow-concentration model and compared with measured lateral downstream CO2 export. Total water export over the hydrological year from the hillslope was 230 mm yr−1 compared with 270 mm yr−1 from the riparian zone. This corresponds well (proportional to the relative upslope contributing area) to the annual catchment runoff of 265 mm yr−1. Total CO2 export from the riparian zone to the stream was 3.0 g CO2-C m−2 yr−1. A hotspot for riparian CO2 export was observed at 30–50 cm depth (accounting for 71 % of total riparian export). Seasonal variability was high with export peaks during the spring flood and autumn storm events. Downstream lateral CO2 export (determined from stream water dissolved CO2 concentrations and discharge) was 1.2 g CO2-C m−2 yr−1. Subtracting downstream lateral export from riparian export (3.0 g CO2-C m−2 yr−1) gives 1.8 g CO2-C m−2 yr−1 which can be attributed to evasion losses (accounting for 60 % of export via the aquatic pathway). The results highlight the importance of terrestrial CO2 export, especially from the riparian zone, for determining catchment aquatic CO2 losses and the importance of the CO2 evasion component to carbon export via the aquatic conduit.

scholarly journals Hydrological connectivity inferred from diatom transport through the riparian-stream system

2015 ◽  
Vol 19 (7) ◽  
pp. 3133-3151 ◽  
Author(s):  
N. Martínez-Carreras ◽  
C. E. Wetzel ◽  
J. Frentress ◽  
L. Ector ◽  
J. J. McDonnell ◽  
...  
Keyword(s):  
Overland Flow ◽  
Riparian Zone ◽  
Stream Water ◽  
Soil Surface ◽  
Species Assemblages ◽  
Hydrological Connectivity ◽  
Diatom Species ◽  
Hydrograph Separation ◽  
Algal Groups ◽  
Runoff Events

Abstract. Diatoms (Bacillariophyta) are one of the most common and diverse algal groups (ca. 200 000 species, ≈ 10–200 μm, unicellular, eukaryotic). Here we investigate the potential of aerial diatoms (i.e. diatoms nearly exclusively occurring outside water bodies, in wet, moist or temporarily dry places) to infer surface hydrological connectivity between hillslope-riparian-stream (HRS) landscape units during storm runoff events. We present data from the Weierbach catchment (0.45 km2, northwestern Luxembourg) that quantify the relative abundance of aerial diatom species on hillslopes and in riparian zones (i.e. surface soils, litter, bryophytes and vegetation) and within streams (i.e. stream water, epilithon and epipelon). We tested the hypothesis that different diatom species assemblages inhabit specific moisture domains of the catchment (i.e. HRS units) and, consequently, the presence of certain species assemblages in the stream during runoff events offers the potential for recording whether there was hydrological connectivity between these domains or not. We found that a higher percentage of aerial diatom species was present in samples collected from the riparian and hillslope zones than inside the stream. However, diatoms were absent on hillslopes covered by dry litter and the quantities of diatoms (in absolute numbers) were small in the rest of hillslope samples. This limits their use for inferring hillslope-riparian zone connectivity. Our results also showed that aerial diatom abundance in the stream increased systematically during all sampled events (n = 11, 2011–2012) in response to incident precipitation and increasing discharge. This transport of aerial diatoms during events suggested a rapid connectivity between the soil surface and the stream. Diatom transport data were compared to two-component hydrograph separation, and end-member mixing analysis (EMMA) using stream water chemistry and stable isotope data. Hillslope overland flow was insignificant during most sampled events. This research suggests that diatoms were likely sourced exclusively from the riparian zone, since it was not only the largest aerial diatom reservoir, but also since soil water from the riparian zone was a major streamflow source during rainfall events under both wet and dry antecedent conditions. In comparison to other tracer methods, diatoms require taxonomy knowledge and a rather large processing time. However, they can provide unequivocal evidence of hydrological connectivity and potentially be used at larger catchment scales.

scholarly journals Hydrological connectivity as indicated by transport of diatoms through the riparian–stream system

2015 ◽  
Vol 12 (2) ◽  
pp. 2391-2434 ◽  
Author(s):  
N. Martínez-Carreras ◽  
C. E. Wetzel ◽  
J. Frentress ◽  
L. Ector ◽  
J. J. McDonnell ◽  
...  
Keyword(s):  
Riparian Zone ◽  
Stream Water ◽  
Soil Surface ◽  
Species Assemblages ◽  
Hydrological Connectivity ◽  
Diatom Species ◽  
Hydrograph Separation ◽  
Algal Groups ◽  
Landscape Units ◽  
Runoff Events

Abstract. Diatoms (Bacillariophyta) are one of the most common and diverse algal groups (ca. 200 000 species, ≈10–200 μm, unicellular, eukaryotic). Here we investigate the potential of terrestrial and aerophytic diatoms (i.e. diatoms nearly exclusively occurring outside water bodies, on wet, moist or temporarily dry places) to infer surface hydrological connectivity between hillslope–riparian–stream (HRS) landscape units during storm runoff events. We present data from the Weierbach catchment (0.45 km2, NW Luxembourg) that quantifies the relative abundance of terrestrial and aerophytic diatom species on hillslopes and in riparian zones (i.e. surface soils, litter, bryophytes and vegetation) and within streams (i.e. stream water, epilithon and epipelon). We tested the hypothesis that different diatom species assemblages inhabit specific moisture domains of the catchment (i.e. HRS units) and, consequently, the presence of certain species assemblages in the stream during runoff events offers the potential for recording if there was or not hydrological connectivity between these domains. We found that a higher percentage of terrestrial and aerophytic diatom species was present in samples collected from the riparian and hillslope zones than inside the stream. However, diatoms were absent on hillslopes covered by dry litter, limiting their use to infer hillslope–riparian zone connectivity in some parts of the catchment. Our results also showed that terrestrial and aerophytic diatom abundance in the stream increased systematically during all sampled events (n = 11, 2010–2011) in response to incident precipitation and increasing discharge. This transport of terrestrial and aerophytic diatoms during events suggested a rapid connectivity between the soil surface and the stream. Diatom transport data was compared to two-component hydrograph separation, and end-member mixing analysis (EMMA) using stream water chemistry and stable isotope data. This research suggests that diatoms were likely sourced exclusively from the riparian zone, since it was not only the largest terrestrial and aerophytic diatom reservoir, but also riparian zone water was a major streamflow source during rainfall events under both wet and dry antecedent condition.

scholarly journals Comparing the runoff decompositions of small testbed catchments: end-member mixing analysis against hydrological modelling

2021 ◽  
Author(s):  
Andrey Bugaets ◽  
Boris Gartsman ◽  
Tatiana Gubareva ◽  
Sergei Lupakov ◽  
Andrey Kalugin ◽  
...  
Keyword(s):  
Auxiliary Information ◽  
Hydrological Modelling ◽  
Rainfall Runoff ◽  
Runoff Generation ◽  
Benchmark Analysis ◽  
In Situ Observations ◽  
Data Generalization ◽  
Runoff Events ◽  
Mountain Taiga

Abstract. This study is focused on the comparison of catchment streamflow composition simulated with three well-known rainfall-runoff (RR) models (ECOMAG, HBV, SWAT) against hydrograph decomposition onto the principal constituents evaluated from End-Member Mixing Analysis (EMMA). There used the data provided by the short-term in-situ observations at two small mountain-taiga experimental catchments located in the south of Pacific Russia. All used RR models demonstrate that two neighboring small catchments disagree significantly in mutual dynamics of the runoff fractions due to geological and landscape structure differences. The geochemical analysis confirmed the differences in runoff generation processes at both studied catchments. The assessment of proximity of the runoff constituents to the hydrograph decomposition with the EMMA that makes a basis for the RR models benchmark analysis. We applied three data aggregation intervals (season, month and pentad) to find a reasonable data generalization period ensuring results clarity. In terms of runoff composition, the most conformable RR model to EMMA is found to be ECOMAG, HBV gets close to reflect specific runoff events well enough, SWAT gives distinctive behavior against other models. The study shows that along with using the standard efficiency criteria reflected proximity of simulated and modelling values of runoff, compliance with the EMMA results might give useful auxiliary information for hydrological modelling results validation.

scholarly journals Carbon dioxide transport across the hillslope–riparian–stream continuum in a boreal headwater catchment

2014 ◽  
Vol 11 (11) ◽  
pp. 15585-15619 ◽  
Author(s):  
F. I. Leith ◽  
K. J. Dinsmore ◽  
M. B. Wallin ◽  
M. F. Billett ◽  
K. V. Heal ◽  
...  
Keyword(s):  
Riparian Zone ◽  
Headwater Streams ◽  
Stream Water ◽  
Storm Events ◽  
Carbon Export ◽  
Carbon Dioxide Transport ◽  
Stream Surface ◽  
Co2 Concentrations ◽  
Daily Water ◽  
Headwater Catchment

Abstract. Headwater streams export CO2 as lateral downstream export and vertical evasion from the stream surface. CO2 in boreal headwater streams generally originates from adjacent terrestrial areas, so determining the sources and rate of CO2 transport along the hillslope–riparian–stream continuum could improve estimates of CO2 export via the aquatic pathway, especially by quantifying evasion at higher temporal resolutions. Continuous measurements of dissolved CO2 concentrations and water table were made along the hillslope–riparian–stream continuum in the Västrabäcken sub-catchment of the Krycklan Catchment, Sweden. Daily water and CO2 export from the hillslope and riparian zone were estimated over one hydrological year (October 2012–September 2013) using a flow-concentration model and compared with measured lateral downstream CO2 export. Total water export over the hydrological year from the hillslope was 230 mm yr-1 compared with 270 mm yr-1 from the riparian zone. This corresponds well (proportional to the relative upslope contributing area) to the annual catchment runoff of 265 mm yr-1. Total CO2 export from the riparian zone to the stream was 3.0 g CO2-C m-2 yr-1. A hotspot for riparian CO2 export was observed at 30–50 cm depth (accounting for 71% of total riparian export). Seasonal variability was high with export peaks during the spring flood and autumn storm events. Downtream lateral CO2 export (determined from stream water dissolved CO2 concentrations and discharge) was 1.2 g CO2-C m-2 yr-1. Subtracting downstream lateral export from riparian export (3.0 g CO2-C m-2 yr-1) gives 1.8 g CO2-C m-2 yr-1 which can be attributed to evasion losses (accounting for 60% of export via the aquatic pathway). The results highlight the importance of terrestrial CO2 export, especially from the riparian zone, for determining catchment aquatic CO2 losses and the importance of the CO2 evasion component to carbon export via the aquatic conduit.

scholarly journals High-frequency measurements of dissolved organic carbon quantity and quality in a headwater catchment

2019 ◽  
Author(s):  
Benedikt J. Werner ◽  
Andreas Musolff ◽  
Oliver J. Lechtenfeld ◽  
Gerrit H. de Rooij ◽  
Marieke R. Oosterwoud ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
High Frequency ◽  
Riparian Zone ◽  
Aridity Index ◽  
Quality Parameters ◽  
Riparian Zones ◽  
Statistical Regression ◽  
Seasonal Scale ◽  
Headwater Catchment

Abstract. Increasing dissolved organic carbon (DOC) exports from headwater catchments impact the quality of downstream waters and pose challenges to water supply. The importance of riparian zones for DOC export from catchments in humid, temperate climates has generally been acknowledged, but the hydrological controls and biogeochemical factors that govern mobilization of DOC from riparian zones remain elusive. A one-year high-frequency (15 minutes) dataset from a headwater catchment in the Harz Mountains (Germany) was analyzed for dominant patterns in DOC concentration (CDOC) and optical DOC quality parameters SUVA254 and S275-295 (spectral slope between 275 nm and 295 nm) on event and seasonal scale. Quality parameters and CDOC systematically changed with increasing fractions of high-frequency quick flow (Qhf) and antecedent hydroclimatic conditions, defined by the following metrics: Aridity Index (AI60) of the preceding 60 days, mean temperature (T30) and discharge (Q30) of the preceding 30 days and the quotient T30/Q30 which we refer to as discharge-normalized temperature (DNT30). Selected statistical regression models for the complete time series (R² = 0.72, 0.64 and 0.65 for CDOC, SUVA254 and S275-295, resp.) captured DOC dynamics based on event (Qhf and baseflow) and seasonal-scale predictors (AI60, DNT30). The relative importance of seasonal-scale predictors allowed for the separation of three hydroclimatic states (warm & dry, cold & wet and intermediate). The specific DOC quality for each state indicates a shift in the activated source zones and highlights the importance of antecedent conditions and its impact on DOC accumulation and mobilization in the riparian zone. The warm & dry state results in high DOC concentrations during events and low concentrations between events and thus can be seen as mobilization limited, whereas the cold & wet state results in low concentration between and during events due to limited DOC accumulation in the riparian zone. We conclude that the high concentration variability of DOC in the stream can be explained by only a few controlling variables. These variables can be linked to DOC source activation by discharge events and the more seasonal control of DOC production in riparian soils.

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