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 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 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 Examination of aerial diatom flushing across watersheds in Luxembourg, Oregon and Slovakia for tracing episodic hydrological connectivity

2015 ◽  
Vol 63 (3) ◽  
pp. 235-245 ◽  
Author(s):  
Laurent Pfister ◽  
Carlos E. Wetzel ◽  
Núria Martínez-Carreras ◽  
Jean François Iffly ◽  
Julian Klaus ◽  
...  
Keyword(s):  
Water Source ◽  
Interdisciplinary Studies ◽  
Transport Processes ◽  
Hydrological Connectivity ◽  
Freshwater Species ◽  
Rainfall Runoff ◽  
Holistic View ◽  
Preliminary Examination ◽  
Open Questions ◽  
Runoff Events

Abstract Hydrological processes research remains a field that is severely measurement limited. While conventional tracers (geochemicals, isotopes) have brought extremely valuable insights into water source and flowpaths, they nonetheless have limitations that clearly constrain their range of application. Integrating hydrology and ecology in catchment science has been repeatedly advocated as offering potential for interdisciplinary studies that are eventually to provide a holistic view of catchment functioning. In this context, aerial diatoms have been shown to have the potential for detecting of the onset/cessation of rapid water flowpaths within the hillslope-riparian zone-stream continuum. However, many open questions prevail as to aerial diatom reservoir size, depletion and recovery, as well as to their mobilisation and transport processes. Moreover, aerial diatoms remain poorly known compared to freshwater species and new species are still being discovered. Here, we ask whether aerial diatom flushing can be observed in three catchments with contrasting physiographic characteristics in Luxembourg, Oregon (USA) and Slovakia. This is a prerequisite for qualifying aerial diatoms as a robust indicator of the onset/cessation of rapid water flowpaths across a wider range of physiographical contexts. One species in particular, (Hantzschia amphioxys (Ehr.) Grunow), was found to be common to the three investigated catchments. Aerial diatom species were flushed, in different relative proportions, to the river network during rainfall-runoff events in all three catchments. Our take-away message from this preliminary examination is that aerial diatoms appear to have a potential for tracing episodic hydrological connectivity through a wider range of physiographic contexts and therefore serve as a complementary tool to conventional hydrological tracers.

scholarly journals Low hydrological connectivity after summer drought inhibits DOC export in a forested headwater catchment

2021 ◽  
Vol 25 (9) ◽  
pp. 5133-5151
Author(s):  
Katharina Blaurock ◽  
Burkhard Beudert ◽  
Benjamin S. Gilfedder ◽  
Jan H. Fleckenstein ◽  
Stefan Peiffer ◽  
...  
Keyword(s):  
Riparian Zone ◽  
Hysteresis Loops ◽  
Hydrological Connectivity ◽  
Summer Drought ◽  
Carbon Cycles ◽  
Relative Contribution ◽  
Doc Export ◽  
Key Driver ◽  
Doc Load

Abstract. Understanding the controls on event-driven dissolved organic carbon (DOC) export is crucial as DOC is an important link between the terrestrial and the aquatic carbon cycles. We hypothesized that topography is a key driver of DOC export in headwater catchments because it influences hydrological connectivity, which can inhibit or facilitate DOC mobilization. To test this hypothesis, we studied the mechanisms controlling DOC mobilization and export in the Große Ohe catchment, a forested headwater in a mid-elevation mountainous region in southeastern Germany. Discharge and stream DOC concentrations were measured at an interval of 15 min using in situ UV-Vis (ultraviolet–visible) spectrometry from June 2018 until October 2020 at two topographically contrasting subcatchments of the same stream. At the upper location (888 m above sea level, a.s.l.), the stream drains steep hillslopes, whereas, at the lower location (771 m a.s.l.), it drains a larger area, including a flat and wide riparian zone. We focus on four events with contrasting antecedent wetness conditions and event size. During the events, in-stream DOC concentrations increased up to 19 mg L−1 in comparison to 2–3 mg L−1 during baseflow. The concentration–discharge relationships exhibited pronounced but almost exclusively counterclockwise hysteresis loops which were generally wider in the lower catchment than in the upper catchment due to a delayed DOC mobilization in the flat riparian zone. The riparian zone released considerable amounts of DOC, which led to a DOC load up to 7.4 kg h−1. The DOC load increased with the total catchment wetness. We found a disproportionally high contribution to the total DOC export of the upper catchment during events following a long dry period. We attribute this to the low hydrological connectivity in the lower catchment during drought, which inhibited DOC mobilization, especially at the beginning of the events. Our data show that not only event size but also antecedent wetness conditions strongly influence the hydrological connectivity during events, leading to a varying contribution to DOC export of subcatchments, depending on topography. As the frequency of prolonged drought periods is predicted to increase, the relative contribution of different subcatchments to DOC export may change in the future when hydrological connectivity will be reduced more often.

Elucidating sources and pathways of dissolved organic carbon in a small, forested catchment – A qualitative assessment of stream, soil and shallow groundwater

2021 ◽  
Author(s):  
Katharina Blaurock ◽  
Phil Garthen ◽  
Benjamin S. Gilfedder ◽  
Jan H. Fleckenstein ◽  
Stefan Peiffer ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Dissolved Organic Carbon ◽  
Soil Water ◽  
Riparian Zone ◽  
Stream Water ◽  
Shallow Groundwater ◽  
Drinking Water Treatment ◽  
Base Flow ◽  
Qualitative Assessment ◽  
Fluorescence Characteristics

<p>Dissolved organic carbon (DOC) constitutes the biggest portion of carbon that is exported from soils. During the last decades, widespread increases in DOC concentrations of surface waters have been observed, affecting ecosystem functioning and drinking water treatment. However, the hydrological controls on DOC mobilization are still not completely understood.</p><p>We sampled two different topographical positions within a headwater catchment in the Bavarian Forest National Park: at a steep hillslope (880 m.a.s.l.) and in a flat and wide riparian zone (770 m.a.s.l.). By using piezometers, pore water samplers (peepers) and in-stream spectrometric devices we measured DOC concentrations as well as DOC absorbance (A<sub>254</sub>/A<sub>365</sub> and SUVA<sub>254</sub>) and fluorescence characteristics (fluorescence and freshness indices) in soil water, shallow ground water and stream water in order to gain insights into the DOC source areas during base-flow and during precipitation events.</p><p>High DOC concentrations (up to 80 mg L<sup>-1</sup>) were found in soil water from cascading sequences of small ponds in the flat downstream part of the catchment that fill up temporarily. The increase of in-stream DOC concentrations during events was accompanied by changing DOC characteristics at both locations, for example increasing freshness index values. As the freshness index values were approaching the values found in the DOC-rich ponds in the riparian zone, these ponds seem to be important DOC sources during events. Our preliminary results point to a change of flow pathways during events.</p>

scholarly journals Contribution of glacial melt to river runoff as determined by stable isotopes at the source region of the Yangtze River, China

2015 ◽  
Vol 47 (2) ◽  
pp. 442-453 ◽  
Author(s):  
Zhaofei Liu ◽  
Zhijun Yao ◽  
Rui Wang
Keyword(s):  
Yangtze River ◽  
Meteoric Water ◽  
Stream Water ◽  
Source Region ◽  
Upstream Region ◽  
The Yangtze River ◽  
Hydrograph Separation ◽  
Water Line ◽  
Total Runoff ◽  
Meteoric Water Line

The primary objective of this study was to quantify the contribution of glacial melt to total runoff in the Gaerqu River catchment, which is located in the source region of the Yangtze River, China. The isotope hydrograph separation method was used to separate glacier melt runoff from total runoff in the catchment. The degree-day method was used to investigate temporal variations in glacial melt runoff. The results showed that the contribution of glacial melt runoff to total runoff was 15.0%. The uncertainty of the separation was ± 3.7% at the confidence level of 95%. Glacial melt runoff was mainly generated in June, July, and August. The runoff coefficient was 0.23 for the catchment. Precipitation-induced runoff constituted 19.9% of the total precipitation, meaning that precipitation loss was >80% across the study period (a hydrological year). The Local Meteoric Water Line (LMWL) of the catchment was fitted as δ2H = 7.75 δ18O + 5.93. This line has a smaller slope and intercept than the Global Meteoric Water Line. The regression-lines for the δ18O and δ2H values of stream water indicated that evaporation was greater over the entire catchment than it was for the upstream region alone.

Understanding the sources and transit times of water contributing streamflow from intermittent headwater catchments in semi-arid areas

2020 ◽  
Author(s):  
Shovon Barua ◽  
Ian Cartwright ◽  
Edoardo Daly ◽  
Uwe Morgenstern
Keyword(s):  
Land Use ◽  
Riparian Zone ◽  
Stream Water ◽  
Land Use Changes ◽  
Significant Proportion ◽  
Catchment Management ◽  
Stream Health ◽  
Headwater Catchments ◽  
Transit Times ◽  
Semi Arid

<p>Intermittent headwater catchments constitute a significant proportion of many stream networks. In semi-arid climates, intermittent headwater streams flow only following periods of sustained rainfall. There is commonly a rapid response of streamflow to rainfall; however, whether this is the input of recent rainfall or displacement of water stored in the catchments for several years is not well known. Understanding the sources and transit times of water that contribute to streamflow is important for the maintenance of stream health and predicting the response of land-use changes.</p><p>The study focuses on two intermittent streams from two contrasting land-use (pasture and forest) in southeast Australia. The native eucalyptus forests in this region were originally cleared for grazing following European settlement <sup>~</sup>180 years ago and then partially replaced by plantation in the last <sup>~</sup>15 years. Stream water and groundwater from the riparian zone adjacent to the streams were sampled between May and October 2018.</p><p>The stream water has <sup>3</sup>H activities of 1.30 to 3.17 TU in the pasture and 1.84 to 3.99 TU in the forest, with higher activities recorded during the higher winter flows. Groundwater from the riparian zone has <sup>3</sup>H activities of 0.16 to 0.79 TU in the pasture and 2.01 to 4.10 TU in the forest. Aside from one riparian zone groundwater sample, all <sup>3</sup>H activities of groundwater in the riparian zone are lower than those of recent local rainfall (<sup>~</sup>2.79 TU). The single high <sup>3</sup>H activity in riparian zone possibly reflects recharge by winter rainfall with higher <sup>3</sup>H activities.</p><p>The mean transit times (MTTs) of water were estimated using a range of tracer lumped parameter models. The riparian zone groundwater has greater MTTs of hundreds of years in the pasture and up to 9 years in the forest. At high streamflow, the stream water has MTTs of <6 years in the pasture and the forest. The MTTs of stream water at low streamflow vary from 15 to 42 years in the pasture and from 3 to 16 years in the forest. The long MTTs of water from streams indicate that the source water is not just recent rainfall, rather water stored in the riparian zone is mobilised at the commencement of flow and recent rainfall makes a larger contribution at higher flows. The observation is consistent with the major ion geochemistry of the stream water, which most closely represents that of the riparian zone groundwater. The differences in MTTs of stream water between two contrasting land-use imply that the streamflow has been being most likely impacted by land-use changes. Thus, it is necessary to improve the strategies for catchment management to protect stream health from land-use practices.</p>

Assessment of recent environmental changes in New Brunswick (Canada) lakes based on paleolimnological shifts in diatom species assemblages

2006 ◽  
Vol 84 (1) ◽  
pp. 151-163 ◽  
Author(s):  
M. Anne Harris ◽  
Brian F. Cumming ◽  
John P. Smol
Keyword(s):  
Climate Change ◽  
New Brunswick ◽  
Environmental Changes ◽  
Environmental Data ◽  
Species Assemblages ◽  
Past Century ◽  
Diatom Species ◽  
Long Term Effects ◽  
Recent Climate

New Brunswick lakes are subjected to multiple environmental stressors, such as atmospheric acid deposition and climate change. In the absence of long-term environmental data, the impacts of these stressors are not well understood. Long-term effects of environmental change on diatom species assemblages were assessed in the sediments of 16 New Brunswick lakes using paleolimnological approaches. A regional trend of increasing Cyclotella stelligera Cleve & Gunrow and decreasing Aulacoseira species complex was recorded in most lakes. Detailed paleolimnological analyses of Wolfe, Cundy, and West Long lakes revealed varying degrees of species change, with assemblage shifts beginning ca. 1900 CE (common era). These species trends are not consistent with acidification. However, linear regression of mean July temperature with time for two New Brunswick historical instrumental temperature records revealed statistically significant warming over the past century. The shift from heavily silicified tychoplanktonic Aulacoseira species to small planktonic diatom species, such as C. stelligera, is consistent with paleolimnological inferences of warming trends recorded in several other lake regions of the Northern Hemisphere. These assemblage shifts are likely due to recent climate change and may be mediated by reduced ice cover and (or) increased thermal stability (decreased lake mixing) during the open water period.

scholarly journals Incorporating experimentally derived streamflow contributions into model parameterization to improve discharge prediction

2021 ◽  
Author(s):  
Andreas Hartmann ◽  
Jean-Lionel Payeur-Poirier ◽  
Luisa Hopp
Keyword(s):  
Parameter Estimation ◽  
Riparian Zone ◽  
Monsoon Season ◽  
Experimental Information ◽  
Model Parameters ◽  
Environmental Tracers ◽  
Hydrograph Separation ◽  
Flow Conditions ◽  
Catchment Scale ◽  
Additional Information

Abstract. Environmental tracers have been used to separate streamflow components for many years. They allow to quantify the contribution of water originating from different sources such as direct runoff from precipitation, subsurface stormflow or groundwater to total streamflow at variable flow conditions. Although previous studies have explored the value of incorporating experimentally derived fractions of event and pre-event water into hydrological models, a thorough analysis of the value of incorporating hydrograph separation derived information on multiple streamflow components at varying flow conditions into model parameter estimation has not yet been performed. This study explores the value of such information to achieve more realistic simulations of catchment discharge. We use a modified version of the process-oriented HBV model that simulates catchment discharge through the interplay of hillslope, riparian zone discharge and groundwater discharge at a small forested catchment which is located in the mountainous north of South Korea subject to a monsoon season between June and August. Applying a Monte Carlo based parameter estimation scheme and the Kling Gupta efficiency (KGE) to compare discharge observations and simulations across two seasons (2013 & 2014), we show that the model is able to provide accurate simulations of catchment discharge (KGE ≥ 0.8) but fails to provide robust predictions and realistic estimates of the contribution of the different streamflow components. Using a simple framework to incorporate experimental information on the contributions of hillslope, riparian zone and groundwater to total discharge during four sub-periods, we show that the precision of simulated streamflow components can be increased while remaining with accurate discharge simulations. We further show that the additional information increases the identifiability of all model parameters and results in more robust predictions. Our study shows how tracer derived information on streamflow contributions can be used to improve the simulation and predictions of streamflow at the catchment scale without adding additional complexity to the model. The complementary use of temporally resolved observations of streamflow components and modelling provides a promising direction to improve discharge prediction by representing model internal dynamics more realistically.

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