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Nitrogen Biogeochemistry and Surface–Subsurface Exchange in Streams
... For the field case study presented here the streambed characterisation did vary between the methods used. The multilevel minipiezometer samples indicated a stream reach characterised by reduced conditions and anoxia, leading to a decrease in pore-water nitrate and increase in pore-water ammonium (Dahm et al., 1998;Duff and Triska, 2000;Lansdown et al., 2016;Lansdown et al., 2014;Naranjo et al., 2015). This was reflected in the vertical profiles of mean porewater concentration values obtained with the multilevel minipiezometers, which indicated surface water high in nitrate and low in ammonium penetrating the subsurface. ...
... There was then a decrease in pore-water nitrate and increase in pore-water ammonium with depth ( Fig. 4a and d). The DET gel data indicated a stream reach characterised by areas of oxygenated sediment, leading to a few points of high porewater nitrate concentration (Dahm et al., 1998;Duff and Triska, 2000;Holmes et al., 1994;Jones Jr. et al., 1995;Naranjo et al., 2015;Seitzinger, 1994), within a streambed similar to that described in Section 3.1.1 for the multilevel mini-piezometer data. ...
... In contrast, the Minipoint data indicated a stream reach characterised by oxidising conditions, leading to high pore-water nitrate and low pore-water ammonium concentrations (Dahm et al., 1998;Duff and Triska, 2000). The mean pore-water concentration profiles obtained from the Minipoints indicated a decrease in pore-water nitrate coupled with an increase in pore-water ammonium with depth ( Fig. 4b and e). ...
Biogeochemical gradients in streambeds are steep and can vary over short distances often making adequate characterisation of sediment biogeochemical processes challenging. This paper provides an overview and comparison of streambed pore-water sampling methods, highlighting their capacity to address gaps in our understanding of streambed biogeochemical processes. This work reviews and critiques available pore-water sampling techniques to characterise streambed biogeochemical conditions, including their characteristic spatial and temporal resolutions, and associated advantages and limitations. A field study comparing three commonly-used pore-water sampling techniques (multilevel mini-piezometers, miniature drivepoint samplers and diffusive equilibrium in thin-film gels) was conducted to assess differences in observed nitrate and ammonium concentration profiles. Pore-water nitrate concentrations did not differ significantly between sampling methods (p-value = 0.54) with mean concentrations of 2.53, 4.08 and 4.02 mg l−1 observed with the multilevel mini-piezometers, miniature drivepoint samplers and diffusive equilibrium in thin-film gel samplers, respectively. Pore-water ammonium concentrations, however, were significantly higher in pore-water extracted by multilevel mini-piezometers (3.83 mg l−1) and significantly lower where sampled with miniature drivepoint samplers (1.05 mg l−1, p-values <0.01). Differences in observed pore-water ammonium concentration profiles between active (suction: multilevel mini-piezometers) and passive (equilibrium; diffusive equilibrium in thin-film gels) samplers were further explored under laboratory conditions. Measured pore-water ammonium concentrations were significantly greater when sampled by diffusive equilibrium in thin-film gels than with multilevel mini-piezometers (all p-values ≤0.02).
The findings of this study have critical implications for the interpretation of field-based research on hyporheic zone biogeochemical cycling and highlight the need for more systematic testing of sampling protocols. For the first time, the impact of different active and passive pore-water sampling methods is addressed systematically here, highlighting to what degree the choice of pore-water sampling methods affects research outcomes, with relevance for the interpretation of previously published work as well as future studies.
... The positive correlation between CO 2 , CH 4 , and NH + 4 indicates that concentrations of these chemical species were high within the same areas of the streambed, likely due to the breakdown of organic matter and anaerobic conditions within the streambed (Baker et al., 2000;Duff and Triska, 2000). These conditions decrease the rate of nitrification, therefore, less NH + 4 is converted to NO − 3 and conditions are suitable for denitrification to reduce NO − 3 , explaining why the negative correlation between these two nutrients was not significant. ...
... These conditions decrease the rate of nitrification, therefore, less NH + 4 is converted to NO − 3 and conditions are suitable for denitrification to reduce NO − 3 , explaining why the negative correlation between these two nutrients was not significant. The positive correlation between NO − 3 , NO − 2 , and N 2 O likely reflects their involvement in similar reaction processes e.g., nitrification and denitrification (Kendall, 1998;Duff and Triska, 2000;Trimmer et al., 2006). A significant correlation was expected but was only observed between NO − 3 and N 2 O. ...
Streams and rivers are globally important in the carbon and nitrogen cycles due to high carbon and nitrogen turnover rates and contribute disproportionately to global greenhouse gas (GHG) emissions relative to their areal coverage. The hyporheic zone may be a hotspot of biogeochemical reactivity within fluvial ecosystems resulting in high rates of nutrient attenuation and associated GHG production. Controls on streambed nutrient cycling and particularly GHG production remain insufficiently understood. In this study, porewater concentrations of nutrients (NH4+, NO3-, NO2-) and GHGes (CO2, CH4, N2O) were measured alongside surface water breakthrough curves (BTC) of conservative (uranine) and reactive tracers [resazurin (raz)-resorufin (rru)] to provide insights into often assumed correlations between in-stream advective transport and transient storage metrics, and streambed biogeochemistry. Streambed biogeochemical concentrations were significantly correlated with advective transport time but not with dispersion and transient storage. The effect of advective transport time varied between chemical species, with NH4+, CO2, and CH4 exhibiting positive correlations and NO3-, NO2-, and N2O displaying negative correlations with advective transport time and vice versa for long-term storage. These findings increase knowledge of the relationship between hydrological drivers and streambed chemistry, potentially highlighting areas of the streambed expected to have elevated nutrients and GHGs. This improved understanding may allow chemical species to be effectively targeted by morphological restoration, which will aid in effective pollution and climate remediation.
... Hyporheic flow processes control flow path distributions, exchange rates, exchange volumes, travel and residence times of water (and waterborne compounds) across the riverbed (Bencala and Walters 1983;Wörman et al. 2002;Marion et al. 2008;Mojarrad et al. 2019a). These variables bear a substantial signature on the biogeochemical cycling of nutrients and pollutants in the sediments and on the development of microbial and macroinvertebrate communities therein (Fischer et al. 2005;Boano et al. 2010;Marzadri et al. 2010; Bardini et al. 2012;Duff and Triska 2000;Battin et al. 2008;Peralta-Maraver et al. 2018). ...
... Hyporheic fluxes-together with water retention times in the sediments-are critical controls for biochemical cycling Summary of the variable levels and replicates in the experimental design. The three levels of the bedform morphology (B) and bacterial dilution (S) are denoted as: B0 (flat sediment); B3 (three bedforms); B6 (six bedforms); S1 (dilution 1:10 1 ); S3 (dilution 1:10 3 ); S6 (dilution 1:10 6 ). in both experimental and in environmental settings (Arnon et al. 2013;Boano et al. 2014;Duff and Triska 2000;Battin et al. 2008;Runkel 2007;Krause et al. 2009). The hydraulic conductivity of the sediments modulates hyporheic fluxes and, in turn, it controls water retention times in the hyporheic zone. ...
Hyporheic exchange (HE) contributes to the biogeochemical turnover of macro- and micro-pollutants in rivers. However, the spatiotemporal complexity and variability of HE hinder understanding of its role in the overall functioning of riverine ecosystems. The present study focuses on investigating the role of bacterial diversity and sediment morphology on HE using a multi-flume experiment. A fully coupled surface–subsurface numerical model was used to highlight complex exchange patterns between surface water and the underlying flow field in the sediments. Under the experimental conditions, the surface water flow induced by bedforms has a prominent effect on both local trajectories and residence time distributions of hyporheic flow paths, whereas mean hyporheic retention times are mainly modulated by average surface flowrates. In case of complex bedform morphologies, the numerical model successfully reproduces the HE estimated by means of salt dilution tests. However, the 2D numerical representation of the system falls short in predicting HE in absence of bedforms, highlighting the intrinsic complexity of water circulation patterns in real scenarios. Finally, results show that higher bacterial diversities in the stream sediments can significantly reduce hyporheic fluxes. This work provides a framework to interpret micropollutants turnover in light of the underlying physical transport processes in the hyporheic zone. The study emphasizes the importance of better understanding the tradeoff between physically driven transport processes and bacterial dynamics in the hyporheic zone to quantify the fate of pollutants in streams and rivers.
... carbon (C), N) availability within these environments (Boulton et al. 1998;Grimm and Fisher 1984;Mulholland et al. 2000;Pinay et al. 2009;Zarnetske et al. 2011). Streambed sediments, therefore, have the potential to cause significant nutrient attenuation, leading to reductions in NO 3 concentrations and subsequent improvements in surface water quality, ecosystem services and ecosystem health (Duff and Triska 2000;Rivett et al. 2008a, b;Wang et al. 2012), however, this may be accompanied by associated N 2 O emissions. The controls and drivers of streambed nutrient attenuation and N 2 O production are insufficiently understood. ...
... concentrations likely result from high rates of nitrification or the relatively low OM content of the gravel-dominated sediments (Table 1) resulting in less NH 4 ? released from organic matter mineralisation (Duff and Triska 2000). Although anammox may also be present, the high concentrations of NO 2 and low concentrations of NH 4 ? ...
Agricultural streams receive large inputs of nutrients, such as nitrate (NO3⁻) and ammonium (NH4⁺), which impact water quality and stream health. Streambed sediments are hotspots of biogeochemical reactivity, characterised by high rates of nutrient attenuation and denitrification. High concentrations of nitrous oxide (N2O) previously observed in stream sediments point to incomplete denitrification, with sediments acting as a potentially significant source of global N2O. We investigated the effect of sediment type and seasonal variation on denitrification and N2O production in the streambed of an agricultural UK stream. Denitrification was strongly controlled by sediment type, with sand-dominated sediments exhibiting potential rates of denitrification almost 10 times higher than those observed in gravel-dominated sediments (0.026 ± 0.004 N2O–N μg g⁻¹ h⁻¹ for sand-dominated and 0.003 ± 0.003 N2O–N μg g⁻¹ h⁻¹ for gravel-dominated). In-situ measurements supported this finding, with higher concentrations of NO3⁻, nitrite (NO2⁻) and N2O observed in the porewaters of gravel-dominated sediments. Denitrification varied substantially between seasons, with denitrification increasing from winter to autumn. Our results indicate highest NO3⁻ reduction occurred in sand-dominated sediments whilst highest N2O concentrations occurred in gravel-dominated sediments. This suggests that finer-grained streambeds could play an important role in removing excess nitrogen from agricultural catchments without producing excess N2O.
... The ratio between reaction time and residence time is critical to predicting if a certain reaction will occur along a GW or HZ flow path or within suspended particulates (e.g. Duff and Triska, 2000). If the residence time is at least as long as the reaction time for N 2 O production, N 2 O will produced. ...
... The nature and relative importance of subsurface exchange influencing N 2 O processes vary in response to stream geomorphology and scale. The amount of streamflow that moves through the HZ, termed the hyporheic exchange, depends on discharge, hydraulic conductivity, and stream geomorphology (Duff and Triska, 2000;Anderson et al., 2005;Gooseff et al., 2006;Tonina, 2012). On a small scale, bed forms such as ripples and dunes cause head gradients that induce advective flow in and out of the HZ (Cardenas et al., 2004). ...
Atmospheric concentrations of the powerful greenhouse gas nitrous oxide (N 2 O) have increased dramatically over the last 100 years, and part of these emissions come from streams and rivers. N 2 O production has been more carefully studied in soils, but runoff of reactive nitrogen, likely from fertilizer, influences lotic N 2 O emissions. N 2 O production and consumption are strongly microbially mediated and mostly involve oxidation and reduction of the reactive nitrogen species ammonia, nitrate, and nitrite. Of the four main pathways leading to N 2 O production in soils and sediments, incomplete denitrification is likely the globally dominant N 2 O generating pathway and is favored by elevated nitrate concentrations, suboxic conditions, and sufficient organic carbon to promote reduction. The two pathways that oxidize ammonia, nitrifier denitrification and nitrification, are favored with higher concentrations of dissolved oxygen and ammonia. It is often difficult to distinguish these two pathways in field settings, but most evidence suggests that nitrifier-denitrification is likely the globally more significant of the two. The fourth reaction pathway is dissimilatory nitrate reduction to ammonia (DNRA), in which N 2 O may be produced from intermediate nitrite. This pathway is more recently discovered, and its global relevance remains uncertain. The key variables influencing N 2 O cycling, concentrations of the primary reactants (nitrate and ammonia), organic carbon, and dissolved oxygen (DO), may vary temporally with season and time of day. Increasing nitrate and ammonia generally result in higher N 2 O production. Elevated carbon availability generally promotes denitrification. However, N 2 O yield is generally higher when carbon is less available or less reactive. Efforts to quantify N 2 O in lotic settings include mostly studies of N 2 O dissolved in or emitted from surface water, with fewer studies of N 2 O produced or emitted from sediments. With some exceptions and limits, N 2 O emissions are generally positively correlated with nitrate concentration (and in some cases, ammonia concentration). Most studies observe more N 2 O emissions with low DO. Lotic N 2 O emissions were generally higher in the warmer months and at night. Most studies assume a denitrification source for N 2 O, except in the case of high DO and NH 4⁺ , in which nitrification is assumed. Lotic N 2 O production and consumption may take place in the hyporheic zone along groundwater flow paths and in the water column of streams and rivers. Because microbial nitrogen processing requires substrate, influx of reactants, appropriate redox conditions, and intermediate residence times, the hyporheic zone is likely the site of most N 2 O production. However, high rates of N 2 O production may also occur associated with suspended sediments in turbid streams and rivers. Models that combine hydromorphogical and chemical variables are most likely to provide the best predictions of N 2 O emissions. Such models and some observations suggest that N 2 O emissions decrease downstream as sedimentary processes (likely denitrification) decrease relative to processes in the surface water (likely nitrification). Downstream sites could have large N 2 O emissions, however, due to inputs of nitrate or ammonia. Better quantification of lotic N 2 O processing will inform the emission factors incorporated into greenhouse gas budgets. Both quantification and mitigation of N 2 O emissions will benefit from future research that more closely examines the biogeochemical pathways and physical settings for N 2 O production and consumption.
... Thus, also their relevance may change in time with effects on water and solute fluxes as well as reactions. As advection is the dominant process for water and solute fluxes in permeable hyporheic sediments [Elliott and Brooks, 1997;Packman et al., 2004;Grant et al., 2014], any change in the hydrologic conditions (e.g., during seasons or storm events) will have an impact on hyporheic exchange processes [Wroblicky et al., 1998;Swanson, 1996a, 1996b;Duff and Triska, 2000]. ...
... However, if ammonium concentrations were high compared to nitrate concentrations, a significant amount of nitrate could be produced by nitrification. In turn, this additional nitrate source would possibly increase reaction rates for denitrification [Duff and Triska, 2000;Bardini et al., 2012;Zarnetske et al., 2012]. ...
In this study, we investigate the impact of single stream discharge events on water exchange, solute transport, and reactions in the hyporheic zone below a natural in-stream gravel bar. We set up a reactive transport groundwater model with streamflow scenarios that vary by event duration and peak discharge. A steady ambient groundwater flow field is assumed that results in losing, neutral, or gaining stream conditions depending on the stream stage. Across the streambed dissolved oxygen, organic carbon, and nitrate are transported into the subsurface. Additional nitrate is received from upwelling groundwater. Aerobic respiration and denitrification are simulated for scenarios with different stream solute concentrations. Results show that hyporheic exchange flux, solute transport, and consumption increase during events. However, their intensities depend highly on the interplay between event characteristics and ambient groundwater conditions. During events where reversals in the hydraulic gradient occur stream water and solutes infiltrate deeper into the aquifer where they have more time to react. For those events, the reactive efficiency of the hyporheic zone (solute consumption as fraction of influx) for aerobic respiration and denitrification is up to 2.7 and 10 times higher compared to base flow conditions. The fraction of stream nitrate load consumed in the hyporheic zone increases with stream discharge (up to 150 mg/m²/h), but remains below the value under base flow conditions for weak events. Events also increase denitrification of groundwater borne nitrate, but groundwater nitrate flux to the stream decreases by up to 33% due to temporary gradient reversals.
... (Sheibley et al. 2016). Přímý vstup dusíku do vody ze srážek je méně významný (Duff and Triska 2000). Významnější může být dotace dusíku do povrchových vod podzemními vodami. ...
Climate change is causing a higher frequency of hydrological extremes that affect surface water quality. On changes in water quality due to hydrological drought we are focused in this article. Flows below Q355, which define hydrological drought, were found to be more frequent in most streams in the last two decades than in previous decades. Statistical analysis of changes in water quality is carried out in selected profiles of the river network, in which surface water quality is monitored, and where near the gauging profile is situated. The first preliminary results show that the hydrological conditions impact significantly on abundance of many pollutants, the methods need further improvements and verification. At the same time, in 2023, we selected the localities in which field research is managed to find out attenuation of nutrients and organic pollution in longitudinal profile of the river in a grid of approximately 1 to 2 km downsteam. The first results show that Rakovnický stream under Rakovník, rivers Metuje under Náchodem and Bílovka pod Bílovec are suitable for this research. Interim results from sampling during the hydrological drought in summer confirmed a significant decrease in total nitrogen, ammonia nitrogen and organic pollution. Conversely, the loss of phosphorus after first mixing waste and surface water was downstream minimal.
... La nitrificación, la conversión quimioautotrófica de amonio a nitrato, es una transformación clave en el ciclo del N ya que es el único proceso natural por el cual el amonio puede convertirse en nitrato. Debido al vínculo común entre nitrificación y desnitrificación (el nitrato), estos procesos pueden acoplarse (es decir, las tasas de desnitrificación localizadas dependen del nitrato producido por bacterias nitrificantes cercanas) (Duff y Triska, 2000). ...
... Therefore, counterclockwise flushing behavior could reflect transport and delivery of nitrate from the main channel and upstream tributaries to the backwater whereas clockwise dilution could reflect dilution of groundwater or other more local sources during lower flow periods of the year (Gorski & Zimmer, 2021;Speir et al., 2021). Additionally, nitrate is susceptible to both transformation and removal as it is transported (Duff & Triska, 2000;Gomez-Velez et al., 2015;Helton et al., 2011), These results highlight the spatial and temporal complexity of nitrate sources and pathways in the UMR. More work is necessary to disentangle nitrate dynamics in backwaters in particular given their potential to act as nitrate sinks in the ecosystem (Loken et al., 2018). ...
Shifts in the frequency and intensity of high discharge events due to climate change may have important consequences for the hydrology and biogeochemistry of rivers. However, our understanding of event‐scale biogeochemical dynamics in large rivers lags that of small streams. To fill this gap, we used high‐frequency sensor data collected during four consecutive summers from a main channel and backwater site of the Upper Mississippi River. We identified high discharge events and calculated event concentration‐discharge responses for both physical‐chemical (nitrate, turbidity, and fluorescent dissolved organic matter) and biological (chlorophyll‐a and cyanobacteria) constituents using metrics of hysteresis and slope. We found a range of responses across events, particularly for nitrate. Although fluorescent dissolved organic matter (FDOM) and turbidity exhibited more consistent responses across events, contrasting hysteresis metrics indicated that FDOM was flushed to the river from more distant sources than turbidity. Biological responses (chlorophyll a and cyanobacteria) differed more between sites than physical and chemical constituents. Lastly, we found that the event characteristics best explaining concentration responses differed between sites, with event magnitude more frequently related to responses in the main channel, and antecedent wetness conditions associated with response variation in the backwater. Our results indicate that event responses in large rivers are distinct across the diverse habitats and biogeochemical components of a large floodplain river, which has implications for local and downstream ecosystems as the climate shifts.
... Transport of solutes in streams and rivers is governed by advection-dispersion in the main channel and exchange between the flowing channel and adjacent zones of slow-moving water in both the surface and subsurface, collectively referred to as transient storage zones. Reactions in transient storage zones control the retention and removal of pollutants, which control, in turn, downstream water quality (Battin et al., 2008;Conant Jr et al., 2004;Duff and Triska, 2000;Fuller and Harvey, 2000;Kim et al., 1995;Mulholland et al., 2008;Palumbo-Roe et al., 2012;Schaper et al., 2018) and exports to the atmosphere (Liu et al., 2022). Historically, multiple experiments with different tracers have been used to probe different transient storage pathways (Keefe et al., 2004;McConville et al., 2017). ...
... Nitrogen is a vital component of proteins and nucleic acids and contains around 10% of the dryweight mass of bacteria [8]. Bacteria, fungi, algae, and plants assimilate nitrogen as nitrate, NO 3 − , or ammonium, NH 4 + . ...
He has published more than 200 publications, mainly in statistical and environmental hydrology and hydrometeorology. Saeid Okhravi received his degree in water engineering from IUT, Iran, and currently is a distinguished graduate student in water structure engineering in IUT. He has contributed in more than 10 scientific publications, mainly in surface and groundwater interaction, rainwater harvesting systems, and wastewater treatment. He also has experiences in the construction of artificial wetlands and rain-water harvesting systems.
... Hou et al. (2012) simulated interaction zones at different depths by using columns and found that the nitrate nitrogen degradation rate was strongly correlated with organic matter, iron, and sulfur contents. In a study of nitrogen in the interaction zone, Duff and Triska (2000) found that redox action with DO as the main driving factor occurred in the nitrogen cycle. Through indoor sandbox experiments, Zhang et al. (2019) found that nitrification was positively correlated with the height of the groundwater level in the fluctuation zone, while denitrification was negatively correlated with this height. ...
To study the inorganic nitrogen in the process of interaction of river and groundwater and the changes in the microbial community, a vertical simulation device was used to simulate groundwater recharge to river water (upwelling) and river water recharge to groundwater (downwelling). The inorganic nitrogen concentrations in the soil and water solution as well as the characteristics of the microbial community were assessed to determine the inorganic nitrogen transformation and microbial community response in the heterogeneous interaction zone under hydrodynamic action, and the interaction mechanism between nitrogen transformation and the microbial community in the interaction zone was revealed. The removal rates of NO3⁻-N in the simulated solution reached 99.1% and 99.3% under the two fluid-groundwater conversion modes, and the prolonged hydraulic retention time (HRT) of the oxidization-reduction layer in the fine clay area and the high organic matter content made the inorganic nitrogen transformation process dominated by microorganisms more complete. The denitrification during upwelling, dominated by denitrifying bacteria in Sphingomonas, Pseudomonas, Bacillus, and Arthrobacter, was stronger than that during downwelling. Dissimilatory nitrate reduction to ammonium (DNRA), controlled by some aerobic bacteria in Pseudomonas, Bacillus, and Desulfovibrio, was more intense in downflow mode than upflow mode.
Graphical abstract
... Solutes entering the HZ are exposed to a biogeochemically active environment and may undergo transformation (Boano et al., 2014;Ward, 2016). Both the amount of solute exchange and their retention times have significant implications for biogeochemical processing of nutrients and chemicals (Battin et al., 2008;Conant Jr et al., 2004;Duff & Triska, 2000;Fuller & Harvey, 2000;Kim et al., 1995;Mulholland et al., 2008;Palumbo-Roe et al., 2012;Runkel, 2007;Schaper et al., 2018). Therefore, it is imperative to account for both channel and hyporheic-zone processes in solute transport models in streams. ...
Nonreacting tracer tests capture information about physical processes in transient storage zones including the hyporheic zone (HZ). However, reliably extracting this information from breakthrough curves (BTCs) and distinguishing the effects of in‐channel dispersion and transient storage are well‐known challenges. Using BTCs from a nonreacting tracer test monitored at multiple locations, we explore ways for reliable parameter estimations. The identifiability of parameters is greatly influenced by the choice of forward and inverse modeling frameworks in addition to the quality of the data. Our forward model is a recently proposed multiscale model that uses subgrid transport models written in the Lagrangian form to represent transport along a diverse set of HZ pathways with a shape‐free distribution of travel times. Joint distributions of HZ and channel parameters are estimated using the Markov Chain Monte Carlo technique. Numerical experiments show ambiguity between channel dispersion and HZ transport when the reach length is too short to allow significant solute‐HZ interaction, the observation period is too brief to observe the tailing behavior, or the solute source is spread in time. In contrast, we obtained reliable parameter estimates by simultaneously fitting BTCs observed at different locations in the test reach using a single set of HZ parameters and section‐specific channel areas and dispersion coefficients. This study demonstrates the estimation of travel time distributions, HZ exchange rates, and channel parameters in a new multiscale approach and offers guidance for extracting reliable parameter estimates from multiple BTCs.
... The hyporheic zone may have anoxic or anaerobic conditions because off high microbial activity, Doussan et al.,(1997) and Krause et al.,(2013).If the consumption of oxygen becomes higher than the hydrological oxygen exchange rate, anoxic conditions lead to an oxic-anoxic interface. The reduced and oxidized forms of the nutrients may coexist under such conditions , Duff and Triska (2000). The removal of heavy metals from source water during subsurface passage mainly occurs through sorption, precipitation and ion exchange processes, which depend on the content of the inorganic and organic compounds in the aquifer and the contact time Bourg et al., (1989) and Hülshoff et al., (2009). ...
Abstract
Egypt, such as many countries worldwide, faces a water-related challenges. The production capacity of potable water is ten times less than the consumption rate which leads to that twenty percent of villages in Egypt are suffering from shortage of availability of drinking water. In addition, the existing Water Treatment Plant (WTP) could not work properly because off contamination of surface water system that come from industrial, agricultural, and domestic activities. On the other hand, water quality standards become more stringent and consequently the cost of water treatment is increasing. In addition, chlorination (traditional disinfectant method) by-products may be linked to heart, lung, kidney, liver, reproductive problems including miscarriage rate, and central nervous system damage. Therefore, there is a need for new alternative water treatment technology.
River Bank Filtration (RBF) Technology is found to be a natural, green, sustainable and cost-effective treatment or pretreatment technology for drinking water. Naturally, water from river flows through the river banks towards the aquifer. A chemical, physical, and biological reactions take place through the aquifer porous media so, pollutant concentrations can be mitigated. RBF is a nature and green water treatment mechanism that can attenuates contaminant concentrations to standards limit. RBF principle has been used extensively in Europe over hundred years along the Elbe and Rhine rivers for domestic water production. Nowadays, the application of this technique has been extended in countries such as USA, India, China, Brazil, Colombia, Korea, and Egypt.
Recently, Egyptian government has relied on River Bank Filtration (RBF) to save drinking and industrial water with less cost and high quality, even during shock loads from flash flood, accident and contaminant spills, seasonal algae blooms, and their toxins, or siltation at the intake points.
The promising potential of RBF in Egypt are found to be the favorable hydrogeological conditions. In addition, the capital and operating costs of the RBF units are lower, compared to conventional water treatment plants. Economical wise, RBF had higher Net Present Value (NPV) and Payback Period (PBP) values, indicating sound economic viability.
This study aims to overview the potential of River Bank Filtration (RBF) as an alternative treatment technology for drinking water. It succinctly reviews and summaries recent research progress in RBF, which will be helpful in facilitating future works.
... We observed limited restoration effect on most inorganic nutrient concentrations, but did detect differences in biologically derived nutrients. Much of the nutrient processing that occurs in the HZ is attributed to microbial metabolism, which requires DOC that comes from the breakdown of POM [74,75]. Increased channel complexity and hyporheic exchange promote the entrainment of POM into hyporheic sediments, and thus provide greater opportunity for DOC consumption via microbial metabolism [31,41,43]. ...
All cities face complex challenges managing urban stormwater while also protecting urban water bodies. Green stormwater infrastructure and process-based restoration offer alternative strategies that prioritize watershed connectivity. We report on a new urban floodplain restoration technique being tested in the City of Seattle, USA: an engineered hyporheic zone. The hyporheic zone has long been an overlooked component in floodplain restoration. Yet this subsurface area offers enormous potential for stormwater amelioration and is a critical component of healthy streams. From 2014 to 2017, we measured hyporheic temperature, nutrients, and microbial and invertebrate communities at three paired stream reaches with and without hyporheic restoration. At two of the three pairs, water temperature was significantly lower at the restored reach, while dissolved organic carbon and microbial metabolism were higher. Hyporheic invertebrate density and taxa richness were significantly higher across all three restored reaches. These are some of the first quantified responses of hyporheic biological communities to restoration. Our results complement earlier reports of enhanced hydrologic and chemical functioning of the engineered hyporheic zone. Together, this research demonstrates that incorporation of hyporheic design elements in floodplain restoration can enhance temperature moderation, habitat diversity, contaminant filtration, and the biological health of urban streams.
... Hyporheic exchange flow (HEF), the movement of water from the channel into the hyporheic zone and back, allows solutes to access those reactive zones. As a result, hyporheic exchange flow is important in the biogeochemical processing of nutrients (Duff and Triska, 2000;Böhlke et al., 2004;Mulholland et al., 2008), organic carbon (Grimm and Fisher, 1984;Battin et al., 2008), metals (Bourg and Bertin, 1993;Fuller and Harvey, 2000;Palumbo-Roe et al., 2012), and organic contaminants (Kim et al., 1995;Conant et al., 2004;Schaper et al., 2018). ...
Efforts to include more detailed representations of biogeochemical processes in basin-scale water quality simulation tools face the challenge of how to tractably represent mass exchange between the flowing channels of streams and rivers and biogeochemical hotspots in the hyporheic zones. Multiscale models that use relatively coarse representations of the channel network with subgrid models for mass exchange and reactions in the hyporheic zone have started to emerge to address that challenge. Two such multiscale models are considered here, one based on a stochastic Lagrangian travel time representation of advective pumping and one on multirate diffusive exchange. The two models are formally equivalent to well-established integrodifferential representations for transport of non-reacting tracers in steady stream flow, which have been very successful in reproducing stream tracer tests. Despite that equivalence, the two models are based on very different model structures and produce significantly different results in reactive transport. In a simple denitrification example, denitrification is two to three times greater for the advection-based model because the multirate diffusive model has direct connections between the stream channel and transient storage zones and an assumption of mixing in the transient storage zones that prevent oxygen levels from dropping to the point where denitrification can progress uninhibited. By contrast, the advection-based model produces distinct redox zonation, allowing for denitrification to proceed uninhibited on part of the hyporheic flowpaths. These results demonstrate that conservative tracer tests alone are inadequate for constraining representation of mass transfer in models for reactive transport in streams and rivers.
... Explaining bacterioplankton community taxonomic composition with instantaneous stream chemistry conditions is complicated by temporal changes in the source and flow path of water entering a channel Dahlke et al., 2012;Moatar et al., 2017). Seasonal changes in hydrology and environmental parameters affect the concentration, form, and downstream availability of organic and inorganic matter necessary for, or inhibitory to, microbial function (Duff and Triska, 2000;Hendricks and White, 2000). ...
Stream bacterioplankton communities, a crucial component of aquatic ecosystems and surface water quality, are shaped by environmental selection (i.e., changes in taxa abundance associated with more or less favorable abiotic conditions) and passive dispersal (i.e., organisms’ abundance and distribution is a function of the movement of the water). These processes are a function of hydrologic conditions such as residence time and water chemistry, which are mediated by human infrastructure. To quantify the role of environmental conditions, dispersal, and human infrastructure (dams) on stream bacterioplankton, we measured bacterioplankton community composition in rivers from sub-alpine to urban environments in three watersheds (Utah, United States) across three seasons. Of the 53 environmental parameters measured (including physicochemical parameters, solute concentrations, and catchment characteristics), trace element concentrations explained the most variability in bacterioplankton community composition using Redundancy Analysis ordination. Trace elements may correlate with bacterioplankton due to the commonality in source of water and microorganisms, and/or environmental selection creating more or less favorable conditions for bacteria. Bacterioplankton community diversity decreased downstream along parts of the stream continuum but was disrupted where large reservoirs increased water residence time by orders of magnitude, potentially indicating a shift in the relative importance of environmental selection and dispersal at these sites. Reservoirs also had substantial effects on community composition, dissimilarity (Bray-Curtis distance) and species interactions as indicated by co-occurrence networks. Communities downstream of reservoirs were enriched with anaerobic Sporichthyaceae, methanotrophic Methylococcaceae, and iron-transforming Acidimicrobiales, suggesting alternative metabolic pathways became active in the hypolimnion of large reservoirs. Our results identify that human activity affects river microbial communities, with potential impacts on water quality through modified biogeochemical cycling.
... Thus, direct and indirect experimental evidence is consistent with denitrification of stream NO 3 − as an important source of N 2 O within these streams, though likely not the only source. Numerous studies, in Sugar Creek and elsewhere, have shown that denitrification in streams primarily takes place during hyporheic flow (Duff and Triska, 2000;Harvey et al., 2013;Quick et al., 2016;Reeder et al., 2018;Zarnetske et al., 2011). Subsurface flow results in suboxic or anoxic conditions required to promote denitrification. ...
Concentrations and emissions of greenhouse gases CO2, CH4, and N2O commonly are examined individually in aquatic environments in which each is expected to be relatively important; however, their co-occurrence and dynamic interactions in fluvial settings could provide important information about their controlling biogeochemical processes and potential contributions to global climate change. Spatial and temporal variability of CH4, N2O, and CO2 concentrations were measured from June 1999 to September 2003 in two nitrate-rich (40–1200 μM) streams draining agricultural land in the midwestern USA that differed ~13-fold in flow. Seasonal (biweekly), diel (hourly), and transport-oriented (reach-scale) sampling approaches were compared. Dissolved gas concentrations exceeded atmospheric equilibrium values up to 700- and 16-fold, for CH4 and N2O, respectively. Mean concentrations were higher in the larger stream than in the smaller stream. In both streams, CH4 emissions were generally higher in summer-fall and negatively correlated with flow and NO3⁻ concentration while N2O emissions were generally higher in winter/spring and positively correlated with flow and NO3⁻. In the small stream, diel variations in the concentrations, emissions, and isotopic compositions of CH4, N2O, and NO2⁻ resulted from diel variations in sources, sinks, and air-water gas exchange velocities. Seasonal mean total (CH4 + N2O) area-normalized emission rates, expressed as CO2 warming potential equivalents, were similar for the two streams, but the total reach-scale emission rate for the larger stream, including CO2, was about 2.9 times that of the smaller stream (131.6 vs 46.0 kg CO2 equivalents km⁻¹ day⁻¹, respectively). The CH4 contribution to this flux was 9–28%, despite the relatively high NO3⁻ and O2 concentrations in the streams, indicating contributions from upwelling groundwater or reactions in streambed sediment.
... The combination of high grain surface area, curvilinear flow paths that induce shear with porous media flows, and unique biogeochemistry enhances microbial reactions relative to SW or deeper GW (Bandopadhyay et al., 2018;Lautz & Fanelli, 2008;Triska et al., 1989). One particularly important hyporheic reaction is denitrification (Duff & Triska, 2000;Gomez-Velez et al., 2015;Zarnetske et al., 2012) as complete denitrification removes excess nitrogen, a widespread pollutant in SW and GW (Dubrovsky et al., 2010). Reactive nitrogen from agricultural runoff and human/livestock sewage (Braun, 2007) is converted from NO 3 − to unreactive N 2 in anoxic conditions in the presence of labile dissolved organic carbon (DOC) (Spanning et al., 2007). ...
The hyporheic zone, where surface water (SW) and groundwater (GW) interact in shallow sediments beneath rivers, is uniquely reactive and attenuates pollutants. Mixing of reactants from SW and GW enables mixing‐dependent (MD) reactions, which may be the last opportunity for GW contaminants to react before entering SW. Yet little is known about hyporheic MD reactions, particularly how they respond to daily or seasonal SW fluctuations or sediment heterogeneity. We used MODFLOW and SEAM3D to simulate non‐mixing‐dependent (NMD) aerobic respiration and MD denitrification in a riverbed dune with nitrate from SW and dissolved organic carbon from GW. We varied SW heads and heterogeneity of sediment hydraulic conductivity. For longer‐term fluctuations (i.e., seasons), increasing SW depth from 0.1 to 1.0 m increased NMD aerobic respiration by 270% and MD denitrification by 78% in homogeneous sediment. MD reactions thus were controlled by mixing zone length or size and would be stronger when SW stage is elevated, for example, during wintertime. Adding sediment heterogeneity to the long‐term scenarios, particularly by increasing hydraulic conductivity correlation length, increased flow focusing and consequently increased MD denitrification by 20–30%. By contrast, the net effect of daily SW fluctuations on MD denitrification in homogeneous sediment was minor. In sum, SW fluctuations are an important control on hyporheic MD reactions, primarily by controlling mixing zone length. The hyporheic zone may attenuate nitrate in upwelling GW plumes, but temporal fluctuations may be considerable as quantified above.
... If the consumption of oxygen exceeds the hydrological oxygen exchange rate, anoxic conditions lead to an oxic-anoxic interface. The reduced and oxidized forms of the nutrients may coexist under such conditions (Duff and Triska, 2000). ...
Riverbank filtration (RBF) is a surface water filtration method for drinking water through the banks and bed of a river, using extraction wells located near the water body in order to ensure direct aquifer recharge. As the surface water travels through the sediments, contaminants, such as suspended and colloidal solids and pathogenic microorganisms, are removed. Apart from water quality improvement, RBF has the advantage of reducing peak concentrations which commonly pass through a river. RBF has been widely used in Europe, USA and, nowadays, in some Asian countries (e.g., South Korea, India, China).
Latin-American and specifically Colombian river basins, have been suffering a continuous
deterioration, leading to high suspended sediment loads being transported by the rivers. The RBF technology has not been proven yet in highly turbid waters, in which the excessive transport of suspended sediments threatens sustainable operation. Clogging of both the riverbed and deeper aquifer may increase flow resistance, reducing water revenues over the course of time.
To assess the feasibility of RBF for highly turbid river waters in Colombia, a combination of field and laboratory research was conducted – both in the Netherlands and Colombia. In Colombia, the studies were done at the Cinara institute's Research and Technology Transfer (R&TT) Station for drinking water and at the Fluid Mechanics lab. The station is located at the Northeast of Cali, Colombia, and was built at the premises of the main water treatment plant of Cali, Puerto Mallarino. In the Netherlands, the laboratory work was done at the Delft University of Technology, running infiltration column experiments at the Sanitary Engineering lab and the flume experiments at the Fluid Mechanics lab.
In addition, an extensive review of the literature was carried out to determine the feasibility of using the RBF for highly turbid sources. Considering the inexistence of the RBF experiences in highly turbid waters, and the unfamiliarity of the technology in Latin-America, the inclusion of the RBF technology in the decision-making process for solving drinking water problems in Colombia made it necessary to compare the technology under the multicriteria analysis methodology by developing a framework structured for the selection of alternatives based on the investment, operation and maintenance requirements, sludge management, environmental impact, vulnerability issues, current legal aspects and social acceptance. Considering these criteria, it was concluded that the RBF technology is a feasible, and more reliable alternative than other water treatment technologies.
Deep bed and cake clogging, and its renewability are highly linked to the particulate matter characteristics. Therefore, field research in Colombia was executed to characterize the suspended particulate matter of a highly turbid river (Cauca River) to have seasonal
information on the composition and particle size distribution, and then to have a starting point for the development of the laboratory studies. Characterization of the particulate matter in the Cauca River has shown that the total suspended solids concentration did not depend on river flows, but merely on precipitation events in the basin due to the erosion of soils. A high scattering was obtained between total suspended solids concentration and turbidity values, potentially due to the different characteristics contributing to both parameters, such as true color and particle size. Seasonal tracing of particulate matter suspended in the Cauca River showed slight differences in the composition and particle size distribution. A slightly higher content of particles smaller than 2 μm was found during rainy conditions due to changes in vegetation coverage and decomposed organic matter in the runoff. Although the differences seem to be minor, further studies demonstrated a considerable impact of their characteristics on clogging and self-cleansing of the particulate matter and, therefore, in the infiltration capacity recovery.
The renewability of the infiltration capacity due to streambed and aquifer clogging and their opposite self-cleansing because of scouring forces was studied. This analysis was performed with emphasis on the river bottom, where lower velocities are expected in these areas and therefore greater sediment accumulation at higher risk of clogged pores, by using infiltration columns inserted into horizontal tilting flumes. Natural infiltration rate recovery at low shear stresses was possible during simulated riverbank filtration tests with water consisting of a mixture of different sediments. Clay and silt behaved very differently, due to the difference in cohesiveness. Clay was found to produce a persistent sticky cake layer, whereas silt penetrated deeper into the bed, both resulting in a poor recovery of infiltration rate.
Altogether it may be concluded that natural recovery of infiltration capacity during RBF of
highly turbid waters is expected to occur, as long as the river carries a mixture of suspended sediments and the grains in the streambed are not too coarse (about 0.2-0.8 mm in diameter as tested in this research).
... The HZ, as the saturated interface between surface water and groundwater, has been recognized as an important buffer and refugial zone which provides fundamental ecosystem services and functioning [Brunke and Gonser, 1997, Boulton, 2007, Krause et al., 2011b. The often enhanced chemical reactivity found at aquifer-river interfaces [Boulton et al., 1998, Fisher et al., 1998, Mulholland et al., 2000, Pinay et al., 2009, Lewandowski and Nützmann, 2010 is controlled by (1) steep redox-gradients (2) high abundances of organic matter and microorganisms [Jones et al., 1995, Fisher et al., 1998, Chafiq et al., 1999, Duff and Triska, 1990, Hinkle et al., 2001, Findlay et al., 2003, Hill and Cardaci, 2004, Storey et al., 2004, and (3) hyporheic flow paths and hyporheic residence times [Bencala, 1993, Jones et al., 1995, Fisher et al., 1998, Duff and Triska, 2000, Zarnetske et al., 2011. The comprehensive understanding of the ecohydrological and biogeochemical functioning of hyporheic streambed environments, therefore, requires detailed knowledge of magnitude, spatial patterns, and temporal dynamics of groundwater-surface water exchange within the streambed at multiple scales. ...
The concept of hydrologic connectivity summarizes all flow processes that link separate regions of a landscape. As such, it is a central theme in the field of catchment hydrology, with influence on neighboring disciplines such as ecology and geomorphology. It is widely acknowledged to be an important key in understanding the response behavior of a catchment and has at the same time inspired research on internal processes over a broad range of scales. From this process-hydrological point of view, hydrological connectivity is the conceptual framework to link local observations across space and scales. This is the context in which the four studies this thesis comprises of were con ducted. The focus was on structures and their spatial organization as important control on preferential subsurface flow. Each experiment covered a part of the conceptualized flow path from hillslopes to the stream: soil profile, hillslope, riparian zone, and stream. For each study site, the most characteristic structures of the investigated domain and scale, such as slope deposits and peat layers were identified based on preliminary or previous investigations or literature reviews. Additionally, further structural data was collected and topographical analyses were carried out. Flow processes were observed either based on response observations (soil moisture changes or discharge patterns) or direct measurement (advective heat transport). Based on these data, the flow-relevance of the characteristic structures was evaluated, especially with regard to hillslope to stream connectivity. Results of the four studies revealed a clear relationship between characteristic spatial structures and the hydrological behavior of the catchment. Especially the spatial distribution of structures throughout the study domain and their interconnectedness were crucial for the establishment of preferential flow paths and their relevance for large-scale processes. Plot and hillslope-scale irrigation experiments showed that the macropores of a heterogeneous, skeletal soil enabled preferential flow paths at the scale of centimeters through the otherwise unsaturated soil. These flow paths connected throughout the soil column and across the hillslope and facilitated substantial amounts of vertical and lateral flow through periglacial slope deposits. In the riparian zone of the same headwater catchment, the connectivity between hillslopes and stream was controlled by topography and the dualism between characteristic subsurface structures and the geomorphological heterogeneity of the stream channel. At the small scale (1 m to 10 m) highest gains always occurred at steps along the longitudinal streambed profile, which also controlled discharge patterns at the large scale (100 m) during base flow conditions (number of steps per section). During medium and high flow conditions, however, the impact of topography and parafluvial flow through riparian zone structures prevailed and dominated the large-scale response patterns. In the streambed of a lowland river, low permeability peat layers affected the connectivity between surface water and groundwater, but also between surface water and the hyporheic zone. The crucial factor was not the permeability of the streambed itself, but rather the spatial arrangement of flow-impeding peat layers, causing increased vertical flow through narrow “windows” in contrast to predominantly lateral flow in extended areas of high hydraulic conductivity sediments. These results show that the spatial organization of structures was an important control for hydrological processes at all scales and study areas. In a final step, the observations from different scales and catchment elements were put in relation and compared. The main focus was on the theoretical analysis of the scale hierarchies of structures and processes and the direction of causal dependencies in this context. Based on the resulting hierarchical structure, a conceptual framework was developed which is capable of representing the system’s complexity while allowing for adequate simplifications. The resulting concept of the parabolic scale series is based on the insight that flow processes in the terrestrial part of the catchment (soil and hillslopes) converge. This means that small-scale processes assemble and form large-scale processes and responses. Processes in the riparian zone and the streambed, however, are not well represented by the idea of convergence. Here, the large-scale catchment signal arrives and is modified by structures in the riparian zone, stream morphology, and the small-scale interactions between surface water and groundwater. Flow paths diverge and processes can better be represented by proceeding from large scales to smaller ones. The catchment-scale representation of processes and structures is thus the conceptual link between terrestrial hillslope processes and processes in the riparian corridor.
... Flow in floodplain channels likely establishes lateral gradients that drive surface-water/groundwater exchange and hyporheic flow, thus increasing water residence times (Malard et al., 2002). These factors that increase water residence times should enhance denitrification processes by allowing more time for the biogeochemical reaction to occur (Böhlke et al., 2009;Duff & Triska, 2000;Mulholland et al., 2008) and, for this system specifically, would do so over a wide range of flows. At the highest flows, the effect of floodplain channels would be washed out, and we would expect channel orientation to drive river-floodplain exchange (Figure 8c), hyporheic flow, and associated nitrate removal (Boano et al., 2014;Gomez-Velez et al., 2017;Stonedahl et al., 2013). ...
High-resolution topography reveals that floodplains along meandering rivers in Indiana commonly contain intermittently flowing channel networks. We investigated how the presence of floodplain channels affects lateral surface-water connectivity between a river and floodplain (specifically exchange flux and timescales of transport) as a function of flow stage in a low-gradient river-floodplain system. We constructed a two-dimensional, surface-water hydrodynamic model using Hydrologic Engineering Center's River Analysis System (HEC-RAS) 2D along 32 km of floodplain (56 km along the river) of the East Fork White River near Seymour, Indiana, USA, using lidar elevation data and surveyed river bathymetry. The model was calibrated using land-cover specific roughness to elevation-discharge data from a U.S. Geological Survey gage and validated against high-water marks, an aerial photo showing the spatial extent of floodplain inundation, and measured flow velocities. Using the model results, we analyzed the flow in the river, spatial patterns of inundation, flow pathways, river-floodplain exchange, and water residence time on the floodplain. Our results highlight that bankfull flow is an oversimplified concept for explaining river-floodplain connectivity because some stream banks are overtopped and major low-lying floodplain channels are inundated roughly 19 days per year. As flow increased, inundation of floodplain channels at higher elevations dissected the floodplain, until the floodplain channels became fully inundated. Additionally, we found that river-floodplain exchange was driven by bank height or channel orientation depending on flow conditions. We propose a conceptual model of river-floodplain connectivity dynamics and developed metrics to analyze quantitatively complex river-floodplain systems.
... fondamentale des échanges hyporhéiques car les réactions chimiques qui ont lieu dans les sédiments dépendent du temps de contact entre l'eau de surface qui s'infiltre et l'eau souterraine (Hendricks & White 1991, Duff & Triska 2000. ...
Les rivières en tresses sont des grandes rivières alluviales de piémont montagneux à forte dynamique spatio-temporelle et à géomorphologie particulière. Leur cours traverse alternativement de vastes plaines et des rétrécissements de vallées ou canyons. Cette géomorphologie influence fortement les échanges d’eau entre la rivière avec sa nappe souterraine et sur l’épaisseur sédimentaire. Les échanges d’eau entre la rivière et sa nappe se produisent à différentes échelles allant de la vallée jusqu’à des bancs de graviers et peuvent créer des filtres biotiques et abiotiques qui influencent les communautés d’invertébrés. Les canyons créent des zones de moindre épaisseur sédimentaire voire d’absence de sédiments et peuvent représenter de fortes barrières à la dispersion pour des organismes inféodés au milieu sédimentaire souterrain. Ce travail de thèse a cherché à évaluer dans quelle mesure la géomorphologie pouvait donc structurer les communautés d’invertébrés de surface et souterraines et pouvait jouer sur la dispersion d’un organisme souterrain Proasellus walteri. Les différents résultats obtenus ont permis de montrer que la géomorphologie structurait les communautés d’invertébrés en mettant en évidence une forte réponse des communautés souterraines mais pas de surface et créait des zones de forte biodiversité à l’aval des plaines. Les résultats de cette étude ont également permis de conclure sur un effet positif de la géomorphologie des rivières en tresses sur la structuration génétique de P. walteri et de mettre en évidence de grandes tailles de populations ainsi que de fortes capacités de dispersion, permettant d’écarter certaines idées reçues sur le milieu souterrain
... Under rainfall or irrigated conditions, high levels of soluble NO 3 can occur in groundwater due to leaching through the soil profile (Randall and Iragavarapu, 1995). NO 3 then is transported through the saturated zone according to advection-dispersion processes and finally delivered to streams and rivers via groundwater discharge (Duff and Triska, 2000). ...
This paper presents SWAT-MODFLOW-RT3D, a model that couples the semi-distributed watershed model SWAT (Soil and Water Assessment Tool) with the groundwater flow model MODFLOW and the groundwater solute reactive transport model RT3D to simulate nitrate (NO3) fate and transport in a watershed system. The model is based on a recently developed SWAT-MODFLOW model, with RT3D now called as a subroutine within the MODFLOW code to provide a single, stand-alone model code. RT3D uses NO3 concentration of deep percolation water from SWAT and groundwater heads and flows from MODFLOW to simulate spatially-varying groundwater NO3 concentration and NO3 loading to/from streams, with the latter used by SWAT to route NO3 mass through the network. Model use is demonstrated through an application to the Sprague River Watershed (4,100 km2) in Oregon. Other chemical species of interest can be included in the RT3D reaction module in applications of the model to other watersheds.
... Specific sources for the degradation of water quality can be caused by diffuse pollution from fertilizers and pesticides used in agriculture and landscaping, and point sources such as waste-water discharged from treatment facilities or even without treatment. The nutrient enrichment in rivers may cause algal blooms, eutrophication and potentially lead to ecosystem stress, loss of biodiversity and reduces ecosystem function (Brunke and Gonser, 1997;Duff and Triska, 2000;Battin et al., 2016). ...
The functioning of the surface water-groundwater interface as buffer, filter and reactive zone is important for water quality, ecological health and resilience of streams and riparian ecosystems. Solute and heat exchange across this interface is driven by the advection of water. Characterizing the flow conditions in the streambed is challenging as flow patterns are often complex and multidimensional, driven by surface hydraulic gradients and groundwater discharge. This thesis presents the results of an integrated approach of studies, ranging from the acquisition of field data, the development of analytical and numerical approaches to analyse vertical temperature profiles to the detailed, fully-integrated 3D numerical modelling of water and heat flux at the reach scale. All techniques were applied in order to characterize exchange flux between stream and groundwater, hyporheic flow paths and temperature patterns. The study was conducted at a reach-scale section of the lowland Selke River, characterized by distinctive pool riffle sequences and fluvial islands and gravel bars. Continuous time series of hydraulic heads and temperatures were measured at different depths in the river bank, the hyporheic zone and within the river. The analyses of the measured diurnal temperature variation in riverbed sediments provided detailed information about the exchange flux between river and groundwater. Beyond the one-dimensional vertical water flow in the riverbed sediment, hyporheic and parafluvial flow patterns were identified. Subsurface flow direction and magnitude around fluvial islands and gravel bars at the study site strongly depended on the position around the geomorphological structures and on the river stage. Horizontal water flux in the streambed substantially impacted temperature patterns in the streambed. At locations with substantial horizontal fluxes the penetration depths of daily temperature fluctuations was reduced in comparison to purely vertical exchange conditions. The calibrated and validated 3D fully-integrated model of reach-scale water and heat fluxes across the river-groundwater interface was able to accurately represent the real system. The magnitude and variations of the simulated temperatures matched the observed ones, with an average mean absolute error of 0.7 °C and an average Nash Sutcliffe Efficiency of 0.87. The simulation results showed that the water and heat exchange at the surface water-groundwater interface is highly variable in space and time with zones of daily temperature oscillations penetrating deep into the sediment and spots of daily constant temperature following the average groundwater temperature. The average hyporheic flow path temperature was found to strongly correlate with the flow path residence time (flow path length) and the temperature gradient between river and groundwater. Despite the complexity of these processes, the simulation results allowed the derivation of a general empirical relationship between the hyporheic residence times and temperature patterns. The presented results improve our understanding of the complex spatial and temporal dynamics of water flux and thermal processes within the shallow streambed. Understanding these links provides a general basis from which to assess hyporheic temperature conditions in river reaches.
... Compoundspecific isotope analysis as well as combining the SI addition approach with quantitative PCR of potential genes (e.g., Findlay et al. 2011;Vilar-Sanz et al. 2013) would provide a wide range of possibilities to study these complex microbial transformations in the aquatic environment (Boschker and Middleburg 2002;Johnson et al. 2012). Future assessment of other ecological assumptions that are still open to debate may be supported by results of experiments using 13 C and 15 N as tracers, for example: the role of allochthonous C inputs in lakes according to their environmental properties (Pace et al. 2007), the effects of increased N loads in lakes on nitrogen-cycling and food-web structure (Pace et al. 2007), the importance of wetlands and hyporheic zones in the nitrogen transformation at landscape scales (Duff and Triska 2000;Böhlke et al. 2009), the metabolic support of food webs (Pace et al. 2007), the N uptake rates and control variables in benthic regions (Wetzel 2001), the mechanisms of N transformation, storage and export in estuaries (Gribsholt and Boschker 2005), or the seasonal variability of food-web structure due to changes in biotic (basal resources, reproductive or stages of development) and abiotic (temperature, runoff, rainfall or evaporation) constraints (Layman et al. 2012). ...
The addition of stable isotopes (SI) of ¹³C and ¹⁵N has been used to study several aquatic processes, thus avoiding environmental disturbance by the observer. This approach, employed for the last three decades, has contributed to expanding our knowledge of food-web ecology and nutrient dynamics in aquatic systems. Currently, SI addition is considered a powerful complementary tool for studying several ecological and biogeochemical processes at the whole-aquatic-ecosystem scale, which could not be addressed otherwise. However, their contributions have not been considered jointly nor have they been evaluated with a view to assessing the reliability and scope of their results from an ecosystem perspective. We intend to bridge this gap by providing a comprehensive review (78 scientific publications reporting in situ ¹³C/¹⁵N additions at the whole-aquatic-ecosystem scale) addressing the main results arising from their use as tracers. Specifically, we focus on: (i) reasons for SI additions at the whole-ecosystem scale to study ecological processes, (ii) the paradigms resulting from its use and the insights achieved, (iii) uncertainties and drawbacks arising from these SI addition experiments, and (iv) the potential of this approach for tackling new paradigms. SI tracer addition at the ecosystem scale has provided new functional insights into numerous ecological processes in aquatic sciences (importance of subsidies in lakes; heterotrophy dominance in benthic food webs in lakes, wetlands and estuaries; the decrease in N removal efficiency in most aquatic ecosystems due to anthropogenic alteration; the recognition of hyporheic zones and floodplains as hot spots for stream denitrification; and high rates of internal N recycling in tidal freshwater marshes). However, certain constraints such as the high cost of isotopes, the maintenance of the new isotopic steady state, and avoidance of biomass changes in any compartment or pool during tracer addition bear witness to the difficulties of applying this approach to all fields of aquatic ecology and ecosystems. The future development of this approach, rather than expanding to larger and complex aquatic ecosystems, should include other stable isotopes such as phosphorus (P¹⁸O4).
... The multiple temporal and spatial scales and the rate of exchange collectively define the hyporheic residence time of water ). The residence time is an important property of the HZ, because most of the biogeochemical processes that occur in sediments depend on the rate of water flow through them (Mulholland and DeAngelis, 2000;Duff and Triska, 2000). Furthermore, the temporal dynamic that affects the hydrological exchange also produces fluctuations of HZ boundaries (Gibert et al., 1990) and this variation in the size of the HZ determines its influence on both the open channel and the underlying groundwater (Vervier et al., 1992). ...
1)We describe the hierarchical interplay of hydrology, hyporheic ecology and transformation of nutrients and pollutants in the hyporheic zone (HZ). The exchange of water between the surface-subsurface generates the hyporheic exchange flow: the engine that drives the ecological functioning of the HZ. The magnitude and direction of hydrological fluxes in the HZ follow complex spatial patterns, strongly influenced by the tem- poral dynamics of surface flow in rivers.
2) The direction and magnitude of hydrological fluxes also shapes the structure of hyporheic communities (hyporheos). During surface disturbances such as flooding or drought, benthic organisms may also use the HZ as a refuge, although the importance of this role is debated.
3) Streambed organisms differ in their ability to colonize the HZ depending on the biological traits they possess. The reduction in oxygen concentration and pore size with increasing sediment depth imposes a limit on the distribution of macroinvertebrates, which are replaced by a suite of smaller organisms (meiofauna and pro- tists) at deeper sediment layers. Therefore, a concomitant reduction in net biomass and productivity might be expected through depth. However, only a few studies have assessed the contribution of the hyporheos to whole system production, and they have focused only on the fraction of relatively large organisms.
4) The bioreactor ability of the HZ to transform nutrients and pollutants is an important ecosystem service sustained by the life activities of hyporheos. Biofilms have the key role in this process due to their capacity to metabolize a wide range of dissolved compounds, including emerging pollutants. However, the residence time of water in pore sediments (resulting from hyporheic exchange flow) and the rest of the community (constantly reworking the sediments and grazing biofilms) are indirectly involved.
... If the consumption of oxygen exceeds the hydrological oxygen exchange rate, anoxic conditions lead to an oxic-anoxic interface. The reduced and oxidized forms of the nutrients may coexist under such conditions (Duff and Triska, 2000). ...
The poor quality of many Colombian surface waters forces us to seek alternative, sustainable treatment solutions with the ability to manage peak pollution events and to guarantee the uninterrupted provision of safe drinking water to the population. This review assesses the potential of using riverbank filtration (RBF) for the highly turbid and contaminated waters in Colombia, emphasizing water quality improvement and the influence of clogging by suspended solids. The suspended sediments may be favorable for the improvement of the water quality, but they may also reduce the production yield capacity. The cake layer must be balanced by scouring in order for an RBF system to be sustainable. The infiltration rate must remain high enough throughout the river–aquifer interface to provide the water quantity needed, and the residence time of the contaminants must be sufficient to ensure adequate water quality. In general, RBF seems to be a technology appropriate for use in highly turbid and contaminated surface rivers in Colombia, where improvements are expected due to the removal of turbidity, pathogens and to a lesser extent inorganics, organic matter and micro-pollutants. RBF has the potential to mitigate shock loads, thus leading to the prevention of shutdowns of surface water treatment plants. In addition, RBF, as an alternative pretreatment step, may provide an important reduction in chemical consumption, considerably simplifying the operation of the existing treatment processes. However, clogging and self-cleansing issues must be studied deeper in the context of these highly turbid waters to evaluate the potential loss of abstraction capacity yield as well as the development of different redox zones for efficient contaminant removal.
... In-stream cycling of nitrogen is strongly controlled by biota (Horne 1994;Duff and Triska 2000;Wetzel 2001). Success of in-stream biota depends on a limited range of temperature, substrate, water velocity, oxygen content, and light availability (Wetzel 2001) which leads biota to seek out habitats within the stream that meet these criteria. ...
This dissertation describes how different types of transient storage zones affect
the in-stream physical and biological transport and storage of solutes in a large stream
and how this knowledge can be applied to restoration efforts. Transient storage zones
provide unique habitats in streams and influence solute retention by increasing residence
time and exposure to biochemically reactive surfaces. Despite the different hydraulic and
biochemical characteristics of hyporheic (HTS) and surface transient storage (STS)
zones, most modeling studies use a single lumped storage zone, which has likely
contributed to over a decade of contradictory results regarding the relationship between
transient storage and solute removal. The traditional OTIS river solute transport model
was modified to include multiple storage zones (HTS and STS), calculation of uptake
within each stream compartment, and Michaelis-Menten uptake kinetics. Multiple
conservative and reactive tracer tests were conducted at two discharge levels in two
reaches of the lower Truckee River, NV. The modified numerical model was used to fit
trends in the observed data and to simulate hypothetical restoration scenarios.
STS is almost 14 times more influential than HTS on the physical transport of
solutes, as measured by its influence on median transport time, because of fast exchange
rates between the main channel and STS zones in the lower Truckee. HTS zones were
106 times more influential in the biological retention of nitrate due to longer residence
times and greater uptake rates. Results varied between sub-reaches and were dependent
on a combination of geomorphology (discharge, slope, average width, average depth, and
sinuosity,) and the physical and biological characteristics of the storage zones (exchange
rate, size, residence time, and uptake rate).
This work is unique in describing the physical and biological characteristics of
both the hyporheic and surface transient storage zones in a large stream (> 0.5 m3 s-1).
With only physical retention information, STS appears to dominate in-stream transient
storage processes. However, when both physical and biological processes are taken into
account it becomes apparent that HTS dominates in-stream nitrogen removal. Results
suggest that separation of the two transient storage zones is needed for a complete
understanding of solute transport, storage, and removal. This information can help guide
stream restoration activities.
By simulating hypothetical restoration scenarios, this research shows that the size
of the hyporheic transient storage zone is the most important factor for removing N via
denitrification and that a combination of restoration targets—including increased width-to-
depth ratio, sinuosity, and hyporheic size—produces more efficient N removal than the
sum of the removal from individual restoration targets. In-stream N removal can also be
increased by adjusting the fraction of organic versus inorganic N from a point source. A
visual tool depicts the potential for stream restoration activities to significantly increase N
removal via denitrification using the combination of hyporheic size, maximum
denitrification rate, and half saturation concentration for denitrification.
... pathways include nitrification (the conversion of ammonium to nitrate), dissimilatory nitrate reduction to ammonium, and denitrification. Denitrification is of particular interest in eutrophic environments as it results in the permanent loss of nitrogen from ecosystems to the atmosphere in the form of nitrous oxide and dinitrogen gases (Duff and Triska 2000). ...
Channelization and embankment of rivers has led to major ecological degradation of aquatic habitats worldwide. River restoration can be used to restore favourable hydrological conditions for target processes or species. This study is based on rarely available, detailed pre- and post-restoration hydrological data collected from 2007–2010 from a wet grassland meadow in Norfolk, UK. Based on these data, coupled hydrological/hydraulic models were developed of pre-embankment and post-embankment conditions using the MIKE-SHE/MIKE-11 system. Fine-scale plant and chemical sampling was conducted on the floodplain meadow to assess the spatial pattern of plant communities in relation to soil physicochemical conditions. Simulated groundwater levels for a 10-year period were then used to predict changes in plant community composition following embankment-removal. Hydrology was identified as the primary driver of plant community composition, while soil fertility was also important. Embankment removal resulted in widespread floodplain inundation at high river flows and frequent localised flooding at the river edge at lower flows. Subsequently, groundwater levels were higher and subsurface storage was greater. The restoration had a moderate effect on flood-peak attenuation and improved free drainage to the river. Reinstatement of overbank flows did not substantially affect the degree of aeration stress on the meadow, except along the river embankments where sum exceedance values for aeration stress increased from 0 m weeks (dry-grassland) to 7 m weeks (fen). The restored groundwater regime may be suitable for more diverse plant assemblages. However the benefits of flooding (e.g. propagule dispersal, reduced competition) may be over-ridden without management to reduce waterlogging during the growing season, or balance additional nutrient supply from river water. The results from this study suggest that removal of river embankments can increase river-floodplain hydrological connectivity to form a more natural flood-pulsed wetland ecotone, which favours conditions for enhanced flood storage, plant species composition and nutrient retention.
... Hence redox gradients still occur, albeit over short distances, within the hyporheic zone (Hinkle et al., 2001;Boulton et al., 1998). As in riparian zones, areas of high denitrification may be patchy; their distribution is controlled by the stream bed topography and locations where organic debris has accumulated, thus causing anaerobic pockets of high DOC (Duff and Triska 2000). Hinkle et al. (2001) and Sheibley et al. (2003) note that the hyporheic zones of two rivers contain discrete regions in which nitrogen transformations occur. ...
Available at: https://www.gov.uk/government/uploads/system/uploads/attachment_data/file/291473/scho0605bjcs-e-e.pdf
... These three points lie in the depression of Laujar de Andarax, where traditional agricultural activities are quite intense. The peak values may relate to leaching of agricultural NO 3 -, which infiltrates the aquifer and later appears in the flow of the river Andarax (Duff and Triska, 2000;Lamontagne et al., 2005). ...
Interactions between surface water and groundwater (SW-GW) in the Andarax catchment are complex and encourage a diversity of surface waters in the three longest watercourses. The headwaters of the river Andarax flow continuously, but it is temporal in its middle reaches and ephemeral in its lower reaches; these three reaches demonstrate the effect of GW-SW dependence. Water quality is also affected by increases in nitrate and salinity in different stretches. The middle reach of the river Nacimiento carries a permanent flow due to a diffuse discharge of groundwater. In the Tabernas rambla (gulley), there is a perennial saline water flow associated with a discharge of saline groundwater, but this is not continuous over the length of the watercourse. Understanding the diversity of situations linked to GW-SW interactions is essential in this semi-arid area if its water resources are to be managed properly; therefore, these interactions need to be borne in mind when considering the water quality indicators of the surface waters.
Secondary production of invertebrates (macro- and meiofauna) was quantified in the benthic and hyporheic zones of two contrasting streams: a forested stream with a gravel bed and an agricultural stream with a fine-sediment-clogged streambed resulting from runoff. In the forested stream, the hyporheic zone contributed substantially to overall stream production (27%), whereas this contribution was significantly lower in the agricultural stream (6%). Despite the lower hyporheic contribution, whole-stream secondary production in the agricultural stream was three times higher than in the forested stream. This elevated production was primarily driven by the invasive species Potamopyrgus antipodarum.
The hyporheic zone (HZ), where surface water and groundwater interact in sediments beneath streams, presents unique conditions for nutrient dynamics, such as carbon and nitrogen (N) cycling. Organic carbon (OC) in aquatic systems has two distinct forms: dissolved organic carbon and particulate organic carbon (POC). OC affects N reduction and controls the occurrence of denitrification, a primary process by which nitrate (NO3⁻) is removed as gas (N2 or N2O) to the atmosphere. When POC is the predominant form of OC in streams, how POC influences NO3⁻ reduction within a HZ remains unclear. We established a new reactive transport model incorporating POC transport and filtration processes to assess how POC deposition affects NO3⁻ removal. Sediment permeability decreases as POC is filtrated in the streambed. Nitrate influx is reduced due to POC‐induced sediment clogging. The deposited POC in the shallow streambed serves as an OC source and supports higher biogeochemical reaction kinetics because OC is an important substrate promoting microbial activities. The filtrated POC pool enhances denitrification, thus causing a higher NO3⁻ removal efficiency. In contrast, the POC pool is typically assumed to be distributed homogeneously in sediments, potentially causing a significant underestimation of stream‐borne NO3⁻ removal. A lower hydraulic conductivity, a smaller POC grain size, and a larger POC filtration efficiency and in‐stream POC concentration allow for extensive POC deposition within the shallow streambed that favors nitrate removal. This study provides a better understanding of N processing and an accurate estimation of NO3⁻ removal potential in HZs.
Nitrogen (N) and Phosphorus (P) are essential elements for animal nutrition and plant growth. However, over the previous decades, excessive loading of fertilizers in agricultural activities has led to elevated concentrations of N and P contaminations in surface waters and groundwater worldwide and associated eutrophication. Therefore, precisely understanding and representation of water movement and fate and transport of N and P within a complex dynamic groundwater-surface water system affected by agricultural practices is of essential importance for sustaining ecological health of the stream-aquifer environment while maintaining high agricultural productivity. Modeling tools often are used to assess N and P contamination and evaluate the impact of management practices. Such models include land surface-based watershed models such SWAT, and aquifer-based models that simulate spatially-distributed groundwater flow. However, SWAT simulates groundwater flow in a simplistic fashion and therefore is not suited for watersheds with complex groundwater flow patterns and groundwater-surface interactions, whereas groundwater models do not simulate land surface processes.
This dissertation establishes the modeling capacity for assessing the movement, transformation, and storage of nitrate (NO3) and soluble P in intensively managed irrigated stream-aquifer systems. This is accomplished by (1) developing a method to apply the SWAT model to such a system, and includes: designating each cultivated field as an individual hydrologic response unit (HRU), crop rotations to simulate the impact of changing crop types for each cultivated field, including N and P mass in irrigation water, and seepage from earthen irrigation canals into the aquifer; (2) simulating land surface hydrology, groundwater flow, and groundwater-surface water interactions in the system using the coupled flow model SWAT-MODFLOW, with the enhanced capability of linkage between SWAT groundwater irrigation HRUs and MODFLOW pumping cells, and the use of MODFLOW’s EVT package to simulate groundwater evapotranspiration; and (3) linking RT3D, a widely used groundwater reactive solute transport model, to SWAT-MODFLOW to credibly represent of NO3-N and soluble P fate and transport processes in irrigated agroecosystems to evaluate best management practices for nutrient contamination. This last phase will also address the uncertainty in system output (in-stream nutrient loads and concentrations, groundwater nutrient concentrations model predictions).
Each modeling phase is applied to a 734 km2 study region in the Lower Arkansas River Valley (LARV), an alluvial valley in Colorado, USA, which has been intensively irrigated for over 100 130 years and is threatened by shallow water tables and nutrient contamination. Multiple best management practices (BMPs) are investigated to analyze the effectiveness in reducing NO3-N and soluble P contamination in the LARV. These strategies are related to irrigation management, nutrient management, water conveyance efficiency, and tillage operations. The most effective individual BMP in most areas is to decrease fertilizer by 30%, resulting in average NO3-N and soluble P concentrations within the region could be reduced by 14% and 9%, respectively. This individual BMP could lower the average NO3-N concentrations by 19% and soluble P concentrations by 2%. Combinations of using 30% irrigation reduction, 30% fertilization reduction, 60% canal seepage, and conservation tillage are predicted to have the greatest overall impact that can not only provide a decrease of groundwater concentration in NO3-N up to 41% and soluble P concentration up to 8%, but also reduce the median of the in-stream NO3-N and soluble P to meet the Colorado interim standard. As nutrient conditions within the Lower Arkansas River Valley are typical of those in many other intensively irrigated regions, the results of this dissertation and the developed modeling tools can be applied to other watersheds worldwide.
Due to the increase in the use of fertilizers and pesticides, pampean streams are undergoing the consequences of agriculture intensification. However, their natural capacity to process nutrients that may enter in excess is not well known in detail yet.
The main objectives of this thesis were: to estimate phosphate and ammonium uptake in two pampean streams; to analyze the influence of primary production, the biomass of autotrophic communities, the flow and the size of transient storage zone on nutrient retention; and; to evaluate the importance of autotrophic and heterotrophic epipelon uptake and abiotic sediment uptake on nutrient retention.
The study was carried out through two different approaches: seasonal nutrient additions in two streams over an annual cycle and laboratory experiments in artificial streams. Field results indicate that phosphate and ammonium uptake were high in both streams and did not saturate in spite of the elevated background nutrient levels. The analysis of factors influencing uptake metrics suggests that phosphate uptake would mainly rely on heterotrophic demand while ammonium uptake could enhance under more autotrophic conditions.
Laboratory experiments indicate that autotrophic and heterotrophic epipelic activity represents a significant effect on phosphate and ammonium uptake. On the other hand, phosphate abiotic uptake on sediments is another retention mechanism that operates together with biotic uptake. However, the mayor part of this process is reversible. Meanwhile, the influence of ammonium abiotic uptake on sediments was not a significant process.
Owing their capacity to reduce nutrient export of terrestrial inputs, the results of this thesis highlight the importance of headwater pampean streams and their self-purification capacity in processing phosphate and ammonium as well as the key role of this ecosystem service for the maintenance of a good ecological quality of lotic environments.
Antropogeniczna fragmentacja rzek prowadzi do obniżenia poziomu przepływu
genów i efektywnej wielkości populacji, zaburzając równowagę pomiędzy migracją,
selekcją i dryfem genetycznym, mimo że migracja w jednym kierunku (z prądem)
często jest częściowo możliwa. W populacjach ryb łososiowatych zróżnicowanie genetyczne może występować w obrębie poszczególnych systemów rzecznych nawet
na ich krótkich odcinkach. Może być to wyraźnie związane z fizycznymi barierami
utrudniającymi migrację a indukującymi różnicowanie poprzez działanie dryfu genetycznego. Istotność wiedzy odnośnie przepływu genów pomiędzy formą osiadłą
i wędrowną Salmo trutta w izolowanych przez zabudowę hydrotechniczną obszarach
wypływa z dwóch głównych przesłanek: ochrony bioróżnorodności oraz gospodarki
rybackiej w tym przede wszystkim z sytemu zarybień. W celu zbadania tego zagadnienia
przeprowadzono w dorzeczu górnej Parsęty, w wytypowanych dopływach,
na których występują bariery hydrotechniczne uniemożliwiające migrację, analizę
zróżnicowania genetycznego pomiędzy osiadłą i wędrowną formą troci w strefach
ich potencjalnej hybrydyzacji. Zinwentaryzowano w nich gniazda tarłowe troci, a następnie przeprowadzono analizę genetyczną narybku z tych stref i porównano go ze
stadem tarłowym troci wędrownej z rzeki Parsęty i populacjami osiadłymi w odciętych
częściach dorzecza powyżej stref hybrydyzacji. W tym celu wykorzystano panel
13 loci mikrosatelitarnych, a także mikromacierz SNP. Dzięki wykonanym analizom
stwierdzono występowanie zjawiska przepływu genów pomiędzy obiema formami
troci. Stwierdzono także znaczne zróżnicowanie genetyczne pomiędzy odizolowanymi
fragmentami dorzecza. Zaobserwowane różnice wynikają z dwóch głównych
czynników: fragmentacji populacji i zarybiania rybami z odległych linii genetycznych.
Analizie rozsiedlenia poddano 7 obcych gatunków ryb stwierdzonych w rzekach
północnej Polski. Były to: trawianka (Perccottus glenii), czebaczek amurski (Pseudorasbora parva), babka rurkonosa (Proterorhinus semilunaris), babka bycza (Neogobius melanostomus), babka łysa (Babka gymnotrachelus), babka szczupła (Neogobius fluviatilis) i karaś srebrzysty (Carassius gibelio).
Materiałem wyjściowym były wyniki połowów elektrycznych prowadzonych w ramach
badań ichtiofaunistycznych w latach 1995–2018 obejmujących rzeki przymorskie
pomiędzy Odrą i Wisłą, dopływy dolnej Wisły poniżej zapory we Włocławku oraz
dopływy Zalewu Wiślanego. Łącznie w analizie ujęto 1170 stanowisk. Dla wymienionych
7 gatunków ustalono podstawowe wskaźniki biocenotyczne – stałość występowania
i dominację. Najszerzej rozprzestrzeniony był karaś srebrzysty. Dla pozostałych
gatunków liczba stanowisk była niewielka. Babka bycza występowała w przyujściowych
odcinkach cieków uchodzących do Zatoki Gdańskiej i Zalewu Wiślanego. Obecność
pozostałych babkowatych (babki łysej, rurkonosej i szczupłej) związana była głównie
ze środowiskiem Wisły, natomiast czebaczek i trawianka pojawiały się w sąsiedztwie
stawów hodowlanych.
Obserwowane w ostatnich latach zmiany środowiskowe w odniesieniu do rzek
związane z antropopresją i zmianami klimatu skutkują przekształceniem dotychczasowych siedlisk, spadkiem poziomu wód i wzrostem temperatur. Taka sytuacja sprzyja ekspansji nowych, ubikwistycznych gatunków inwazyjnych i zanikowi rodzimych,
stenotopowych gatunków ryb. Wszystkie wymienione gatunki naturalnie rozmnażają
się w północnej Polsce, przez co tworzą samoutrzymujące się populacje. Biorąc pod
uwagę że większość z nich pojawiła się w północnej Polsce dopiero niedawno, w najbliższej przyszłości można się spodziewać ich dalszej ekspansji.
Młodociane węgorze po transformacji u atlantyckich wybrzeży Europy poprzez
cieśniny duńskie wchodzą do Bałtyku, ich część wstępuje do rzek do niego wpadających
i nimi rozprzestrzenia się po całej zlewni. Zmniejszająca się ilość dopływających
do Europy larw węgorza i ich intensywne odłowy powodują, że obecnie do rzek południowego
Bałtyku dociera znacznie mniej ryb niż w przeszłości. Wstępujące węgorze,
głównie z względu na niewielkie rozmiary, bardzo rzadko pojawiają się jako przyłów
w połowach innych ryb. Dlatego aby uzyskać dane na ten temat trzeba zastosować
metody ukierunkowane ściśle na połów/obserwację małych, płynących pod prąd węgorzy.
Badania tego typu prowadzi się najczęściej w miejscach koncentracji węgorzy
np. poniżej spiętrzeń. Ryby próbują pokonać przegrody także wspinając się na nie,
co wykorzystuje się w konstrukcji pułapek.
Systematyczny monitoring wstępujących węgorzy Zakład Ryb Wędrownych Instytutu
Rybactwa Śródlądowego rozpoczął w roku 2011 w ramach Polskiego Planu
Gospodarowania Zasobami Węgorza w Polsce i obecnie kontynuowany jest w ramach
Wieloletniego Programu Zbierania Danych Rybackich. W tym okresie pułapki
umieszczano w 11 miejscach na 9 rzekach, głównie przymorskich. Ilości złowionych
węgorzy były bardzo zmienne, w wielu miejscach nie udało się złowić węgorzy, ale
największy połów wyniósł 1540 ryb (Słupia, 2018 r). W połowach dominowały ryby
między 14 a 16 cm, ale obecne były także dużo mniejsze, poniżej 10 cm, i dużo większe,
ponad 35 cm. Szczyt migracji najczęściej miał miejsce w drugiej połowie lipca, ale
zdarzały się też dość intensywne ciągi nawet w czerwcu lub wrześniu. Zarówno wielkości
ryb jak i terminy migracji różniły się między rzekami. Podstawowym problemem
monitoringu jest bardzo różna i zmienna łowność pułapek w zależności od rozdziału
wody na przegrodzie, technicznych możliwości zamontowania pułapek, a także zmieniających
się warunków hydrologicznych. W dwóch eksperymentach oszacowujących
łowność pułapki uzyskano 4 % (Łupawa, 2018 r) i 56 % (Słupia, 2018 r).
The objectives of this study were to evaluate nutrient delivery, storage, and trophic transfer between the Horsefly River spawning channel and its riparian zone during the 2011 sockeye salmon run and subsequent spring 2012. The hyporheic zone was investigated as a pathway for nutrient exchange, transformation, and storage by analyzing water movement and ammonium concentration. Using stable isotopic analysis, the assimilation and storage of marine-derived nutrients (MDN) were evaluated through multiple trophic levels. Results identified lateral hyporheic flow as a dominant pathway for MDN delivery to deep-rooted vegetation, specifically willow trees <7-m from the streambank. Amphipods and chironomids appeared to assimilate MDN in teh fall and maintained high spring biomass, indicating an important nutrient linkage in the salmon feedback loop. Finally, a temporal reversal in ammonium concentration across the stream-riparian interface and a seasonal shift in nutrient fluxes revealed reciprocal subsidies that highlight the interconnectedness of these adjacent systems.
• Wetlands are often biogeochemical hotspots, and they can remove excess N via denitrification and assimilatory uptake. Wetlands are also susceptible to plant invasions, but the effect of invasive plants on denitrification in freshwater wetland sediments is not well‐studied.
• Two distinct mechanisms suggest the potential for invasive plants to alter denitrification. First, invasive plants often produce more biomass than non‐invasive species, thus potentially providing additional carbon (C) for denitrifiers. Second, some invasive wetland plants funnel more oxygen into the root zone than non‐invasive plants, potentially stimulating coupled nitrification–denitrification.
• Using the push–pull isotope pairing technique, we measured denitrification and coupled nitrification–denitrification in the sediments beneath monoculture plots of Phragmites australis and Typha domingensis, and beneath unvegetated sediments, in an urban wetland in Melbourne, Australia. We also measured pore water nutrient concentrations and calculated the diffusive flux of nutrients from the sediments into the overlying water column.
• We hypothesised that plots containing P. australis would have the highest denitrification and coupled nitrification–denitrification rates, followed by plots containing T. domingensis, with the lowest rates in the unvegetated plots, as a result of higher C and oxygen availability.
• Instead, we found that denitrification and coupled nitrification–denitrification rates were highly variable, with no difference among plot type. However, we did find that diffusive flux of ammonium from the sediments into the water column was lower in the vegetated plots than in the unvegetated plots, suggesting that vegetation enhances wetland N retention via plant assimilatory uptake.
The hyporheic zone (HZ) is the active ecotone between the surface stream and groundwater, where exchanges of nutrients and organic carbon have been shown to stimulate microbial activity and transformations of carbon and nitrogen. To examine the relationship between sediment texture, biogeochemistry, and biological activity in the Columbia River HZ, the grain size distributions for sediment samples were characterized to define geological facies, and the relationships among physical properties of the facies, physicochemical attributes of the local environment, and the structure and activity of associated microbial communities were examined. Mud and sand content and the presence of microbial heterotrophic and nitrifying communities partially explained the variability in many biogeochemical attributes such as C:N ratio and %TOC. Microbial community analysis revealed a high relative abundance of putative ammonia-oxidizing Thaumarchaeota and nitrite-oxidizing Nitrospirae. Network analysis showed negative relationships between sets of co-varying organisms and sand and mud contents, and positive relationships with total organic carbon. Our results indicate grain size distribution is a good predictor of biogeochemical properties, and that subsets of the overall microbial community respond to different sediment texture. Relationships between facies and hydrobiogeochemical properties enable facies-based conditional simulation/mapping of these properties to inform multiscale modeling of hyporheic exchange and biogeochemical processes.
In this chapter, we describe nutrient limitation in stream ecosystems, the problems associated with elevated nutrient loading caused by human activities in the watershed, and how streams process and transform nutrients prior to downstream export. We provide a basic method for quantifying nutrient limitation of stream biofilms using nutrient diffusing substrata. We also detail two advanced methods that can be used to quantify nutrient spiraling within streams using experimental addition approaches: a short-term nutrient release and a ¹⁵N stable isotope tracer addition. Finally, we describe several modifications to the various methods that could expand their application to various research questions or to allow for customization depending on specific research questions. Understanding the nutrient limitation status and quantifying nutrient uptake in streams is vital because these are key components of ecosystem function, providing information on how streams retain nutrients from watersheds prior to downstream export.
Rivinoja, P., Calles, O., Karlsson, S. and S. Lundström. 2010. Effects of small scale hydropower on aquatic fauna. 21 pages. The potential effect of small scale hydropower on aquatic fauna is reviewed, with main focus on fish. At the time when hydropower was introduced, little attention was paid to its negative impact on the environment, yet more recently various drawbacks of hydropower on the environment have been identified. Studies point out that river regulation can have detrimental effects on the local environment and impair the function and structure of river ecosystems. Flow regulations influence the longitudinal, vertical, lateral and temporal exchanges of matter, energy and organisms, which may cause negative effects on aquatic species. The negative effects can roughly be summarised in e.g.; a) hindered fish migration, b) shifts in fish species assemblage and aquatic invertebrate community, c) lowered oxygen content in and close to the bottom substratum. In general both large and small scale hydropower schemes have resembling impact on the local river environment. Most studies in regulated rivers have focused on how the longitudinal connectivity affects the migrations of fish which involves up-and downstream movements along river corridors. To re-establish river connectivity fishways can be constructed. Nevertheless, relatively few studies have evaluated their efficiencies and only a handful have looked at the overall effect of re-establishing connectivity, e.g. if targeted populations are strengthened by the increased habitat availability. Furthermore, just facilitating longitudinal connectivity will not have any long-term effects, unless all essential requirements for different species and life-stages are taken into account. For fish this should include appropriate habitats for spawning, rearing and foraging. The flow alterations occurring in regulated rivers may stress the aquatic fauna and cause limited amounts of appropriate habitats, while also plant dispersal can be restricted. The effects of hydropower on the biota are likely to vary dependent on construction type and specific river environment. Still, the knowledge on long term effects of river regulation seems rather scarce, indicating the need of further research on overall ecological effects in regulated rivers. These studies should address improved migratory corridors and environmentally adapted flow regimes and include assessment of whole the river ecosystems.
Due to a combination of local methanogenesis and high background concentrations in the groundwater, water in the River Lambourn is 51 times supersaturated with methane (162 nmol CH 4 L ⁻¹ ). Pore‐water concentrations of methane in the gravels of the riverbed were much lower throughout the year (71 nmol CH 4 L ⁻¹ ), suggesting significant methane oxidation. To investigate the potential for methane oxidation as a novel chemosynthetic source of carbon to the food web, we made simultaneous measurements, in laboratory chambers, of primary production, respiration, and methane oxidation associated with the gravels. Biomass‐specific net primary production was up to 2.7 µmol O 2 mg ⁻¹ chlorophyll (Chl) h ⁻¹ and was similarly high for respiration (2.7 µmmol O 2 mg ⁻¹ Chl h ⁻¹ ). We also found active methane (CH 4 ) oxidation with the rate increasing in proportion to concentration. At the maximum rate of 0.18 µmol CH 4 mg ⁻¹ Chl h ⁻¹ and a growth efficiency of 0.8, net carbon fixation via methane oxidation was equivalent to 6% of the carbon fixed via net photosynthetic primary production. However, production via methane oxidation could be proportionately much greater under the shade of the profuse instream or riparian vegetation, deep in the gravels, and especially during winter, when light is limiting (< 25 µmol quanta m ⁻² s ⁻¹ ).
This study aims to investigate the physical and chemical effects of interactions between groundwater and surface water (GW–SW)—particularly in streams—on nitrate contamination. The effects of GW–SW interactions are briefly reviewed, with a particular emphasis on processes and environments that influence increases or decreases in nitrate concentration. Then, this paper analyses nitrate concentrations in groundwater and surface water in the western Po plain (Northwestern Italy); this analysis includes the nitrate concentration profiles across the shallow aquifer and intersecting the main streams on the plain. The investigation highlights how the concentration trends are similar, even when nitrate levels in rivers and groundwater are not comparable. The maximum nitrate concentrations in the surface water were generally measured in areas with high-nitrate levels in groundwater. An analysis of the nitrate concentration profiles highlighted the mutual influences of GW–SW. The most important streams on the plain (the Po River and Stura di Demonte River), both of them gaining streams, seem to reduce the nitrate concentrations of groundwater at a study scale. The proposed conceptual model indicates how the near-stream environment (the riparian zone, wetlands, hyporheic zone and shallow organic-rich soils in the near-stream environment) and the groundwater flow systems in shallow and deep aquifers, from the recharge zone to the streams, could dramatically affect the nitrate concentrations.
Bacterial biomass, activity, and production were examined within the hyporheic zone of a sandy-bed, north-temperate stream over three seasons. Date (November, February, and May), zone (upwelling, downwelling), and depth (10 cm, 50 cm into the bed) were significant main effects on bacterial variables. Biomass and production were significantly higher in May than during November and February, and generally higher at the 10cm depth than at the 50cm depth. Activity was higher in the downwelling zone in November followed by a minor peak in May. Production in the downwelling zone in May was 10-fold that of the upwelling zone. Response by bacteria to DOC enrichments (glucose, humic acid) was inconsistent and statistically insignificant. However, some general trends emerged which were consistent with observations for unenriched sediments. Bacterial activity increased with DOC enrichment only in the downwelling zone during November and May. Bacterial production in the downwelling zone increased with DOC enrichment only during November. Hyporheic bacterial patterns reflected generally higher metabolic activities (electron transport activity, thymidine uptake into DNA) within the downwelling zone, a region of greater surface subsurface hydrologic exchange within the streambed and presumably higher DOC quality from surface-derived labile sources.
The groundwater-surface water (GW-SW) ecotone, or hyporheic zone, is an active component of stream ecosystems that influences whole-system metabolism and nutrient retention. Because hydrologic fluxes affect the supply of carbon, nutrients, and oxygen to the GW-SW ecotone, the biogeochemical structure of the ecotone (i.e., nutrient content) and the role of the ecotone in nutrient retention are expected to vary under differing hydrologic conditions. In this paper, we employ an inter-basin comparison of headwater streams to assess the influence of ecosystem hydrology on the structure and functioning of GW-SW ecotones. Specifically, we address how differing rate and extent of GW-SW interaction influences heterogeneity in interstitial nutrient content and how variation in GW-SW interaction alters the role of the ecotone in whole-system nutrient retention. A multiple regression model derived from 6 solute-injection experiments identified the extent and rate of hydrologic exchange between the stream and its aquifer as critical variables that determine the retention of biologically important solutes. This approach emphasizes that the nature of GW-SW interaction is established by catchment geology (i.e., alluvial hydrogeologic properties), is modified by changing discharge within a catchment, and is a strong determinant of nutrient retention. At the landscape scale, identifying catchment geologic composition may be a starting point for comparative studies of GW-SW ecotones that could contribute to a more robust model of lotic ecosystem functioning.
1. This study estimated the importance of in situ denitrification in the nitrate buffering capacities of a riparian forest. 2. Spatial and temporal patterns of in situ denitrification were investigated along a riparian catena. 3. Highest rates of in situ denitrification (up to 78 mgN m(-2) day(-1)) were measured in the riparian forest soils in late winter and early spring. Lowest rates (3 mgN m(-2) day(-1)) were measured in summer and autumn. 4. Whatever the season considered, 30 m of riparian buffer strip were enough to remove all the nitrates coming through the groundwater. 5. Rehabilitation of riparian zones with riparian vegetation together with the maintenance of waterlogged conditions induced by riverflow regulation appear to be a good point from which to start the restoration of buffering capacities of river ecosystems against nitrogen loads.
Nitrification in the hyporheic zone of Sycamore Creek, a Sonoran Desert stream, was examined, focusing on the association between respiration and nitrate production. Subsurface respiration in Sycamore Creek is highest in regions of hydrologic downwelling where organic matter derived from the stream surface is transported into the hyporheic zone. Similarly, nitrification was closely related to hydrologic exchange between the surface and hyporheic zone. Nitrification in downwelling regions averaged 13.1 mu gNO(3)-N . L sediments(-1). h(-1) compared with 1.7 mu gNO(3)-N . L sediments(-1). h(-1) in upwelling regions. Hyporheic respiration also varies temporally as a result of flash floods which scour and remove algae from the stream and thus reduce the pool of organic matter to support subsurface metabolism. Nitrification was also significantly affected by flooding; nitrification increased from an average of only 3.0 mu gNO(3)-N . L sediments(-1). h(-1) immediately following floods to 38.5 mu gNO(3)-N . L sediments(-1). h(-1) late in succession. Nitrification was significantly correlated with hyporheic respiration, supporting the hypothesis that nitrification is fueled by mineralization of organic nitrogen to ammonium. The coupling between subsurface respiration and nitrification is one step in a cyclic interaction between surface and hyporheic zones and serves to transform nitrogen from an organic to inorganic form.
Stream water was locally recharged into shallow groundwater flow paths that returned to the stream (hyporheic exchange) in St. Kevin Gulch, a Rocky Mountain stream in Colorado contaminated by acid mine drainage. Two approaches were used to characterize hyporheic exchange: sub-reach-scale measurement of hydraulic heads and hydraulic conductivity to compute streambed fluxes (hydrometric approach) and reach-scale modeling of in-stream solute tracer injections to determine characteristic length and timescales of exchange with storage zones (stream tracer approach). Subsurface data were the standard of comparison used to evaluate the reliability of the stream tracer approach to characterize hyporheic exchange. The reach-averaged hyporheic exchange flux (1.5 mL s-1 m-1), determined by hydrometric methods, was largest when stream base flow was low (10 L s-1) hyporheic exchange persisted when base flow was 10-fold higher, decreasing by approximately 30%. Reliability of the stream tracer approach to detect hyporheic exchange was assessed using first-order uncertainty analysis that considered model parameter sensitivity. The stream tracer approach did not reliably characterize hyporheic exchange at high base flow: the model was apparently more sensitive to exchange with surface water storage zones than with the hyporheic zone. At low base flow the stream tracer approach reliably characterized exchange between the stream and gravel streambed (timescale of hours) but was relatively insensitive to slower exchange with deeper alluvium (timescale of tens of hours) that was detected by subsurface measurements. The stream tracer approach was therefore not equally sensitive to all timescales of hyporheic exchange. We conclude that while the stream tracer approach is an efficient means to characterize surface-subsurface exchange, future studies will need to more routinely consider decreasing sensitivities of tracer methods at higher base flow and a potential bias toward characterizing only a fast component of hyporheic exchange. Stream tracer models with multiple rate constants to consider both fast exchange with streambed gravel and slower exchange with deeper alluvium appear to be warranted.
A numerical hydrological simulation suggested that water exchange between stream channels and adjacent aquifers is enhanced by convexities and concavities in streambed topography. At St. Kevin Gulch, an effluent stream in the Rocky Mountains of Colorado, subsurface hydraulic gradients and movement of ionic tracers indicated that stream water was locally recharged into well-defined flow paths through the alluvium. Stream water-filled flow paths in the alluvium (referred to as substream flow paths) returned to the stream a short distance downstream (1 to 10 m). Recharge to the substream flow paths occurred where stream water slope increased, at the transition from pools (
The influence of hydrologic linkage between hyporheic and surface subsystems was investigated in sand-bottomed reaches of a desert stream. Direction of hydrologic exchange was measured as vertical hydraulic gradient (VHG) using mini-piezometers. Maps of VHG indicated upwelling (discharge from the interstitial regions into surface water) at the bases of riffles and heads of runs; downwelling (infiltration of surface water into the hyporheic zone) occurred at the bases of runs. Dissolved NO3-N in surface water was higher over or immediately downstream from upwelling zones. Loss of continued supply from the hyporheic zone and intense assimilatory demand by surface autotrophs generated longitudinal declines in NO3-N and lower nutrient concentrations in downwelling zones. Algal standing crop (as chlorophyll a) was significantly higher in upwelling zones than in areas without positive VHG. Postflood trajectories of chlorophyll a indicated that algae at upwelling zones recovered from disturbance significantly faster than those at downwelling zones. Recovery rate was related to supply of NO3-N from enriched interstitial water in the hyporheic zone. Hydrologic linkage integrates surface and hyporheic subsystems and increases ecosystem stability by enhancing resilience of primary producers following flash flood disturbance.
Nitrogen dynamics of Sycamore Creek, Arizona, a lowland Sonoran Desert stream, are described by seven diel input-output budgets at different stages of postflood succession. Hydrologic inputs and outputs of nitrogen and N storage in periphyton, macroinvertebrates, and fish were measured over 24-h periods. Total nitrogen storage in this desert stream (3-9 g/m^2) was lower than that in forest streams of Oregon (12 g/m^2) and Quebec (22 g/m^2). While >99% of nitrogen in the latter systems is in allochthonous detritus, benthic algae and autochthonous detritus comprised @?90% of the total nitrogen pool in the desert stream. Up to 14% of nitrogen was in consumer organisms. Inputs of nitrogen to the stream ecosystem were dominated by dissolved nitrogen, of which 19-60% was inorganic, primarily nitrate. Particulate nitrogen in transport (4-15%of total input) was mostly autochthonous. Inputs of nitrogen exceeded outputs on most study dates. Rates of ecosystem nitrogen retention were as high as 400 mg@?m^2@?d^-1 and outputs exceeded inputs on only one study date. Retention was primarily of inorganic nitrogen and was presumed due to autotrophic assimilation. Nitrogen retention data from the seven budgets were used to evaluate the Vitousek and Reiners (1975) model that patterns of nitrogen retention during succession reflect patterns of net ecosystem production and biomass accumulation. Biomass and stored nitrogen increased asymptotically during a postflood successional sequence at a single site; nitrogen retention during this period accounted for increases in storage. Nitrogen retention among the seven study dates exhibited the predicted successional patterns of increases from early to middle successional stages, followed by late stage declines.
Hydraulic characteristics were measured in artificial streams and in 1st- to 5th-order streams in the Appalachian and Cascade mountains. Appalachian Mountain stream sites at Coweeta Hydrologic Laboratory, North Carolina, were on six Ist-order streams and a 1st- through 4th-order gradient of Ball Creek-Coweeta Creek. Cascade Mountain sites were located on constrained and unconstrained reaches of Lookout Creek, a 5th-order stream in H. J. Andrews Experimental Forest, Oregon. At each site, a tracer solution (chloride or rhodamine WT) was released for 30-180 min and then discontinued. At the downstream end of the release site, the resulting rise and fall of the tracer concentration was measured. These data, along with upstream concentration and measured widths and depths, were used in a computer model to estimate several hydraulic parameters in- cluding transient storage and lateral inflow. Estimated transient storage zone size (A,) ranged from near zero in artificial streams to 2.0 m2 in 5th-order streams. A, was largest relative to surface cross- sectional area (A) at Ist-drder sites where it averaged 1.2 x A, compared with 0.6 x A and 0.1 x A in unconstrained and constrained 5th-order sites, respectively. Where measured, lateral discharge inputs per metre of stream length ranged from 1.9% of instream discharge in Ist-order streams to 0.05% of instream discharge at 5th-order sites. Our results show that surface water exchange with storage zones is rapid and extensive in steep headwater streams and less extensive but still significant at 3rd- through 5th-order sites. An understanding of relationships between stream morphology, storage zone size, and extent of interactions between surface and subsurface waters will assist comparisons of solute dynamics in physically diverse streams.
We investigated nitrogen dynamics over a 15-mo period in the parafluvial zone (the part of the active channel without surface water) of Sycamore Creek, Arizona, a nitrogen-limited Sonoran Desert stream. The parafluvial zone and surface stream are linked hydrologically; thus, nitrogen dynamics in the parafluvial zone potentially influence whole-system functioning. We identified discrete parafluvial flowpaths by following the movement of fluorescent dye through gravel bars over time, sampled subsurface water along these flowpaths, and collected parafluvial sediments for measurement of nitrification rate. Water samples were analyzed for nitrate-N, ammonium-N, dissolved oxygen, temperature, and conductivity. Nitrate-N concentration increased along parafluvial flowpaths, with the largest increases occurring in summer. Although ammonium-N concentration was low and did not vary with season or location on flowpath, dissolved oxygen declined as water moved through parafluvial gravel bars. Net nitrification rate was highest in the summer and at the heads of flowpaths where surface water entered the parafluvial zone, suggesting that nitrification may be dependent upon ammonium, dissolved organic nitrogen, or particulate organic nitrogen imported from the surface stream. Overall, the parafluvial zone of Sycamore Creek was a source of nitrate to the nitrogen-limited surface stream, and may play an important role in the productivity of the stream ecosystem.
Conservative solute injections were conducted in three first-order montane streams of different geological composition to assess the influence of parent lithology and alluvial characteristics on the hydrological retention of nutrients. Three study sites were established: (1) Aspen Creek, in a sandstone–siltstone catchment with a fine-grained alluvium of low hydraulic conductivity (1·3×10⁻⁴ cm/s), (2) Rio Calaveras, which flows through volcanic tuff with alluvium of intermediate grain size and hydraulic conductivity (1·2×10⁻³ cm/s), and (3) Gallina Creek, located in a granite/gneiss catchment of coarse, poorly sorted alluvium with high hydraulic conductivity (4·1×10⁻³ cm/s). All sites were instrumented with networks of shallow groundwater wells to monitor interstitial solute transport. The rate and extent of groundwater–surface water exchange, determined by the solute response in wells, increased with increasing hydraulic conductivity. The direction of surface water–groundwater interaction within a stream was related to local variation in vertical and horizontal hydraulic gradients. Experimental tracer responses in the surface stream were simulated with a one-dimensional solute transport model with inflow and storage components (OTIS). Model-derived measures of hydrological retention showed a corresponding increase with increasing hydraulic conductivity.
Denitrification was measured in hyporheic, parafluvial, and bank sediments of Sycamore Creek, Arizona, a nitrogen-limited Sonoran Desert stream. We used three variations of the acetylene block technique to estimate denitrification rates, and compared these estimates to rates of nitrate production through nitrification. Subsurface sediments of Sycamore Creek are typically well-oxygenated, relatively low in nitrate, and low in organic carbon, and therefore are seemingly unlikely sites of denitrification. However, we found that denitrification potential (C & N amended, anaerobic incubations) was substantial, and even by our conservative estimates (unamended, oxic incubations and field chamber nitrous oxide accumulation), denitrification consumed 5–40% of nitrate produced by nitrification. We expected that denitrification would increase along hyporheic and parafluvial flowpaths as dissolved oxygen declined and nitrate increased. To the contrary, we found that denitrification was generally highest at the upstream ends of subsurface flowpaths where surface water had just entered the subsurface zone. This suggests that denitrifiers may be dependent on the import of surface-derived organic matter, resulting in highest denitrification rate at locations of surface-subsurface hydrologic exchange. Laboratory experiments showed that denitrification in Sycamore Creek sediments was primarily nitrogen limited and secondarily carbon limited, and was temperature dependent. Overall, the quantity of nitrate removed from the Sycamore Creek ecosystem via denitrification is significant given the nitrogen-limited status of this stream.
Removal of nitrogen by denitrification from surficial pathways as well as subsurfce flow takes place in the three dimensional structure of river corridors, wherever the prerequisite conditions for denitrification exist, ie anoxia, available carbon and sufficient nitrate. These factors are under the control of both geomorphology which influences sediment deposition and retention during floods and floodplain vegetation which may be important in providing a carbon source to denitrifying micro-organisms. However, in most European headwaters and main river catchments, agriculture impinges directly upon river banks, leading to an increase of nutrient concentration in aquatic ecosystems. Restoration of river corridors and reactivation of the denitrification process would de-couple the riverine ecosystem from its agricultural catchment, and reduce the impact of pollution in river channels. -from Authors
Hyporheic metabolism in a Sonoran Desert stream was examined, focusing on the sources of detritus supporting hyporheic respiration. Two alternative hypotheses were specifically addressed: (1) organic matter derived from the surface stream supports hyporheic respiration, and (2) detritus buried during flash floods supports hyporheic respiration. As predicted for the surface-derived organic matter hypothesis, respiration was lowest immediately following flash floods and increased significantly with time after flood (P < 0.001). Hyporheic respiration ranged from 0.05 mgO(2) . L sediments(-1). h(-1) immediately following a flash flood to as high as 4.41 mgO(2) . L sediments(-1). h(-1) late in algal succession. Respiration was significantly correlated with surface algal biomass during two spring/summer successional sequences (P < 0.05; partial correlation coefficients 0.58 and 0.88). Respiration was also consistently higher in downwelling than upwelling zones with overall mean rates of 1.12 and 0.46 mgO(2) . L sediments(-1). h(-1), respectively. Respiration exhibited a distinct diel pattern with highest rate coinciding with time of maximum photosynthesis and was also significantly correlated with dissolved organic carbon concentration (P < 0.05), further supporting the hypothesis of hyporheic dependence on algal production. Flash floods bury organic matter that is also respired in the hyporheic zone; however, based upon storage of organic carbon immediately following floods, an average of only 15% of the observed respiration could be supported. We conclude that hyporheic respiration in Sycamore Creek is tightly linked to surface production. It is spatially distributed in biotic ''hot spots'' where surface waters enter hyporheic sediments and is most likely supported by organic matter that is supplied as dissolved organic carbon, perhaps from algal production.
Chloride was injected as a conservative tracer with nitrate to examine nitrate retention (storage plus biotic uptake) and transport in a 327-m reach of a third-order stream draining a forested basin in northwestern California. Prior to injections, diel patterns of nutrient concentrations were measured under background conditions. Nitrate concentration of stream water increased downstream, indicating that the reach was a source of dissolved inorganic nitrogen to downstream communities under background, low-flow conditions, despite uptake by photoautotrophs. At the onset of continuous solute injection over a 10-d period, timing the passage of the solute front indicated that storage dominated nitrate retention. Instantaneous concentration differences at the base of the reach at hour 24 indicated that biotic uptake accounted for 13% of the nitrate amendment while hydrologic storage constituted 29%. -from Authors
The objective of this study was to quantify subsurface nitrogen fluxes between a riparian forest and a 4th-order mountain stream, McRae Creek, for each season of the year and during storms. A network of wells was installed on a gravel bar and a portion of the adjacent floodplain between 1989 and 1992. Water samples were collected to monitor dissolved nitrogen concentrations Advected channel water and ground water were enriched in nitrogen relative to the stream; thus, subsurface flow was a net source of nitrogen to the stream in all seasons of the year and during both base-flow periods and storms. Estimates of the flux of advected channel water and the discharge of ground water were combined with changes in mean nitrogen concentrations along subsurface flow paths to estimate nitrogen inputs to the stream. Discharge of ground water from the conifer-dominated floodplain was the largest source of nitrogen added to the stream; however, more than 50% of this nitrogen was dissolved organic nitrogen. In contrast, two-thirds of the nitrogen from the alder-dominated gravel bar was inorganic. Net nitrogen fluxes from the gravel bar to the stream were lowest during the summer when water table elevations were low. Net fluxes of nitrogen from the gravel bar to the stream were largest during the fall, especially at peak flow during storms when interstitial water in the gravel bar was enriched in NO3-. The estimated annual flux of nitrogen from the riparian forest to McRae Creek was 1.9 g/m(2) of streambed, of which 1.0 g/m(2) was inorganic. Estimated net annual flux was large relative to the estimated input of nitrogen in litterfall, or the nitrogen required to support estimated rates of primary productivity.
An annual energy budget is presented for Bear Brook, a small undisturbed second-order stream in northeastern United States. The ecosystem approach, in which all input and output fluxes of potential energy as organic matter are considered, is used to describe the dynamics of energy flow in a 1,700-m segment of the stream. The annual input of energy to the system is 6,039 Kcal/m2. Over 99% of this is allochthonous, from the surrounding forested watershed or from upstream areas. Autochthonous primary production by mosses accounts for less than 1% of the total energy available to the ecosystem. Algae and vascular hydrophytes are absent from the stream. Meteorologic inputs (litter and throughfall) from the adjacent forest account for 44% of annual energy input. Most of this is in particulate form. The remaining 56% of input enters by geologic vectors (inflowing surface and subsurface waters). Eighty-three per cent of the geologic input and 47% of the total input of energy occur as dissolved organic matter. Approximately 4,730 Kcal/m2 of organic detritus, nearly equally divided between leaves and branches, is stored within the system. The size of this detritus reservoir is stable from year to year. The turnover time of the branch compartment is about 4.2 years; of the leaf compartment, about 1 year. Although much of the annual input of energy is in a dissolved state, dissolved organic matter does not tend to accumulate in the system and displays a very rapid rate of turnover. Sixty-six per cent of annual energy input is exported to downstream areas in stream water. The remaining 34% is lost as heat through consumer activity. Bear Brook is a strongly heterotrophic steady-state system in which import and export of organic matter play a significant role. A conceptual scheme is presented by which import, export, photosynthesis, and respiration may be used to describe the functional dynamics and developmental processes of ecosystems.
A stream solute workshop was held February 1-5, 1989, at The University of Mississippi with the goals of 1) suggesting a conceptual model for stream solute studies that integrates physical, chemical, and biological processes, and 2) identifying advantages and limitations of various methods for studying solute transport and exchanges. Solute dynamics refers to the spatial and temporal patterns of transport and transfers of materials that are chemically dissolved in water. Solute transport and exchange processes can be described by solute transport equations that relate solute concentration to advection, dispersion, groundwater and tributary inputs, transient storage zones, and biotic and abiotic transformations. Studies can be based on these model equations even if a full simulation of a particular system is not attempted. Although no common methodological approach can serve every investigation of solute dynamics, experimental approaches represent a range from greatest control and least realism to least control and greatest realism. The model parameters describe processes that can be investigated in laboratory, chamber, and flume experiments designed to reduce confounding experimental variables. Whole-stream studies, particularly solute injection experiments, provide estimates of solute transfer to and from the water column and can be used to calibrate the simulation models. Transport and transfer models can link experimental results obtained at different scales and increase the opportunity for inter-site comparisons and the extrapolation of results between laboratory, chamber, flume, and whole-stream studies.
The objective of this study was to quantify fluxes of ground water and advected channel water through the shallow aquifer adjacent to a 4th-order mountain stream. A network of wells was installed from 1989 to 1992. Water-table elevations were measured seasonally and during storms. These data were used to calibrate MODFLOW, a 2-dimensional groundwater flow model. The fluxes of water through the subsurface were estimated from the head distributions predicted by the model for 8 steady state model runs bracketing the observed range in baseflow conditions, and for 1 transient simulation of a large storm. The overall pattern of subsurface flow changed little over the course of the year, even though the relative flux of advected channel water and ground water changed among seasons and during storms. Apparently the longitudinal gradient of the main valley, the location of the stream, and the influence of secondary channels determined the pattern of subsurface flows. Subsurface fluxes through a gravel bar were dominated by advected channel water but fluxes through the floodplain were dominated by ground water. Flow rates were positively correlated to estimated stream discharge during base-flow periods, but decreased slightly during storms because of precipitation inputs to the aquifer. The mean residence time of water stored within the aquifer was approximately 10 d for the gravel bar and 30 d for the floodplain during baseflow periods. Even though precipitation during the simulated storm equaled 12% and 23% of the water stored in the gravel bar and the floodplain, respectively, the mean residence time of water remained long.
An Annual nitrogen budget is presented for a small steam draining Watershed 10, H. J. Andrews Experimental Forest, Oregon. The role of allochthonous debris in the input, flux, and export of nitrogen is emphasized in the material balance budget. All material entering the stream channel was presumed to enter the water sometime during the year. Material estimates are based on total channel area. The major annual nitrogen input (1974-1975) was subsurface flow (11.06 g/m^2) as dissolved organic nitrogen (10.56 g/m^2) and nitrate (0.50 g/m^2).Biological inputs of nitrogen amounted to 4.19 g/m^2 as direct terrestrial inputs of: litterfall (1.35 g/m^2), lateral movement (1.78 g/m^2), and throughfall (0.30 g/m^2). Nitrogen fixation on fine wood debris contributed an additional 0.76 g/m^2 based on rates from a nearby watershed. Total nitrogen input was 15.25 g/m^2. The nitrogen pool was dominated by large amounts of particulate organic matter. Coarse wood constituted 32% of the nitrogen pool (3.80 g/m^2) and fine wood fractions 18% (2.18 g/m^2). The coarse wood fraction greatly influenced stream morphology. Fine organic particulates constituted an additional 40% of the nitrogen pool (4.77 g/m^2). DON (dissolved organic nitrogen) export (8.38 g/m^2) was less than input, presumably due to biological uptake associated with litter mineralization, sorption, and chemical flocculation. Due to effective retention of particulate inputs by debris dams, biological processing in the particulate nitrogen pool, and uptake and sorption of DON, most particulate organic inputs increased in nitrogen concentration prior to export. Particulate organic nitrogen input (3.13 g/m^2) was greater than export (2.53 g/m^2). Total annual nitrogen output was 11.36 g/m^2, resulting in a gain of 3.89 g@?m^-^2@?yr^-^1 to the stream. Thus, the stream was not operating on an annual steady state, but on an input-output regime related to the processing of refractory wood debris and resetting by major storms. Although particulate and dissolved nitrogen loss per hectare was small for the 10-ha watershed, these losses passed through or were accumulated in a pool encompassing <1% of the watershed area. This concentration of N in the stream allowed establishment of a separate ecosystem whose processing efficiency and capabilities for nutrient cycling were related to the retention capacity of the channel and nutrient quality of inputs within the reach.
Chloride and nitrate were coinjected into the surface waters of a third-order stream for 20 d to examine solute retention, and the fate of nitrate during subsurface transport. A series of wells (shallow pits) 0.5-10 m from the adjacent channel were sampled to estimate the lateral interflow of water. Two subsurface return flows beneath the wetted channel were also examined. The conservative tracer (chloride) was hydrologically transported to all wells. Stream water was >88% of flow in wells <4 m from the wetted channel. The lowest percentage of stream water was 47% at a well 10 m perpendicular to the stream. Retention of solutes was greater in the hyporheic zone than in the channel under summer low-flow conditions. Nominal travel time (the interval required for chloride concentration to reach 50% of the plateau concentration) was variable by well location, indicating different flow paths and presumably permeability differences in subsurface gravels. Nominal travel time was M 24 h for wells <5 m from the wetted channel. Coinjected nitrate was not conservative. Two wells were significantly (P < .05) higher in nitrate-N than would be predicted from chloride, while four were significantly lower. Wells 2.0-4.0 m from the wetted channel tended to have higher nitrate concentration than predicted, whereas nitrate sink locations tended to have transport distances >4.3 m. The capacity of the hyporheic zone for transient solute storage and as potential biological habitat varies with channel morphology, bed roughness, and permeability. A conceptual model that considers the groundwater-stream water interface as the fluvial boundary is proposed. Emerging paradigms of the riverine network should consider the hyporheic zone and associated nutrient cycling as an integral component of fluvial structure and function.
Inputs and outputs of N, P, K, Ca, Mg and Cl were determined for 4 subwatersheds of the Little River in the Georgia Coastal Plain from 1979-1981. All elements except Cl had greater inputs than outputs on each watershed each year. The general order of streamflow loads was Cl>Ca>K>Mg>N>P. Fertilizer inputs exceeded precipitation inputs for all elements on all watersheds. Outputs of N, P, and K in harvest generally exceeded streamflow loads, but harvest outputs of Ca, Mg, and Cl were generally lower than streamflow loads. The two watersheds with more agricultural land had consistently higher loads of N, K, Ca, Mg, and Cl in streamflow and had NO3-N loads 1.5 to 4.4 times higher than loads from the less agricultural watersheds. Large amounts of N, P, K, Ca, and Mg were not accounted for. About 56 kg.ha-1.yr-1 of N were retained or lost to gaseous emissions from the uplands. -from Authors
Agroecosystems in the southeastern United States Coastal Plain typically have uplands in agriculture with mixed hardwood forests along the stream channels. This study determined the inputs and outputs of waterborne nutrients for the riparian forest ecosystem of an agricultural watershed. Quantities of phreatic groundwater and precipitation nutrient inputs and phreatic and surface nutrient outputs were determined during 1979. Based on input/output budgets, these streamside forests were shown to be effective in retaining N, P, Ca, and Mg. Partial conversion of the riparian forest to cropland was projected to increase NO3-N and NH4-N loads by up to 800%. Total replacement of riparian forest with crops would increase loads of all nutrients studied except organic N, DMRP, and total P. Land managers can maintain the nutrient filtering capacity of the streamside forest by selective harvesting of hardwoods and by maintaining the present hydrologic regime.
1. The flow of water through the sediment layer (underflow) of streams can influence nutrient uptake dynamics and the supply of materials to microbes, meiofauna and macroinvertebrates living within stream sediments. We examined the extent of underflow in Hugh White Creek, a headwater stream in the southern Appalachian Mountains and compared underflow at different depths and at different sites within the stream.
2. Initially rhodamine dye was used to trace the flow of water through the sediments; however, the dye was strongly absorbed by the sediments in Hugh White Creek. Thus rhodamine was not suitable as a tracer of water flow. Chloride reacted conservatively in laboratory experiments and was used as a tracer.
3. The tracer infiltrated the sediments within 5 min to depths of 10 cm at all six sites. Chloride infiltration tended to decrease with depth of sediments at all sites although there was no consistent statistical pattern in chloride concentration with depth for the different sites. Equilibrium between the water column and sediments was reached rapidly, within minutes for the sites with coarse sediments and within a few hours for sites with finer sediments. Minimum rates of chloride infiltration into the sediments ranged between 1.0 cm min−1 for the sites with cobble substrate to 0.2 cm min−1 for sites with fine sand sediments associated with debris dams. These data suggest that underflow may be a major component in the functioning of Appalachian mountain streams.
Undisrupted periphyton communities from a N‐rich (NO 3 ⁻ = 63 µ mol L ⁻¹ ) and pristine (NO 3 ⁻ = 2.9 µ mol L ⁻¹ ) stream were assayed for denitrifying activity (acetylene‐blockage technique) in 40‐L chambers incubated at in situ temperature and nutrient concentrations. Nitrous oxide formation associated with periphyton from the N‐rich stream was immediate and linear (52.1 µ mol N 2 O m ⁻² h ⁻¹ ) in the dark, anaerobic chamber (50 kPa C 2 H 2 ). In the corresponding light, aerobic chamber (50 kPa C 2 H 2 ), N 2 O production was inhibited by 82% (9.3 µ mol N 2 O m ⁻² h ⁻¹ ). Nitrous oxide formation was not associated with periphyton from the pristine stream incubated in situ, either with or without NO ³ ⁻ amendment.
Denitrification estimates made with undisrupted periphyton communities at in situ temperature and nutrient concentrations (40‐L chambers) were less variable than estimates made with periphyton “scrapings” in small flasks (room temperature). The calculated diel periphyton‐associated denitrification rate based on a 14‐h light‐10‐h dark day was 651 µ mol N 2 O m ⁻² d ⁻¹ . The data suggest denitrification within periphyton mats may contribute toward removal of NO ³ ⁻ from N‐rich fluvial environments.
We address the ecological ramifications of variation in hydrologic interaction between streams and alluvial aquifers in catchments with alluvium derived from parent materials of contrasting geologic composition. We present a conceptual model in which solute retention in streams results from hydrologic retention (increased water residence time resulting from surface-groundwater exchange), biological nutrient cycling, and chemical processes. Solute injection experiments were done in study catchments comprised of sandstone- siltstone (site l), volcanic tuff (site 2), and granite-gneiss (site 3). Distribution of an injected conservative tracer (Br) illustrated that rate and extent of surface-water penetration into the alluvial aquifer increased across study catchments as was predicted from increasing alluvial hydraulic conductivity. Concurrently, groundwater inputs at baseflow represented between 13 and 57% of aboveground discharge at upstream transects, indicating bidirectional hydrologic exchange along the study reaches. N : P ratios in surface water ranged from 4 to 16, suggesting strong biotic demand for inorganic N. Coinjection of NaBr and NaNO, revealed longest nitrate uptake length (S,) at site 1, intermediate S, at site 2, and shortest uptake length at site 3. Modeling of transient hydrologic solute storage revealed that S, correlated with hydraulic storage, suggesting an important role for subsurface processes in total nitrate retention.
An experimental injection was performed to study the transport of stream water solutes under conditions of significant interaction with streambed sediments in a mountain pool-and-riffle stream. Experiments were conducted in Little Lost Man Creek, Humboldt County, California, in a period of low flow duringwhich only a part of the bank-full channel held active surface flow. The injection of chloride and several trace cations lasted 20 days. In this report we discuss the results of the first 24 hours of the injection and survey the results of the first 10 days. Solute-streambed interactions of two types were observed. First, the physical transport of the conservative tracer, chloride, was affected by intergravel flow and stagnant watt, zones created by the bed relief. Second, the transport of the cations (strontium, potassium, and lithium) was appreciably modified by sorption onto streambed sediment. In the stream the readily observable consequence of the solute-streambed interactions was an attenuation of the dissolved concentration of each of the tracers. The attenuation in the stream channel occurred concurrently with the storage of tracers in the streambed via both physical and chemical processes. All tracers were subsequently present in shallow wells dug several meters from the wetted part of the channel. Sediment samples collected approximately 3 weeks after the start of the injection contained increased concentrations of the injected cations.
Addition of dry hickory and maple leaves, enclosed in nylon mesh, for 30 hr to a recirculating stream increased dissolved organic carbon (DOC) levels nearly 10‐fold. Bacterial populations which developed rapidly decomposed labile organic carbon and nitrogen compounds in the leaf leachate within 72 hr. Bacteriologically labile and refractory dissolved organic carbon fractions, with T½ decomposition rates of 2 and 80 days, respectively, were present in the leachate. Most refractory dissolved organic nitrogen compounds persisted unmodified for at least 24 days. The processing capacity of woodland streams for natural dissolved organic compounds is much greater than previously believed.
Nutrient cycling in streams occurs in conjunction with downstream transport as spatially distributed process that has been termed spiralling. The intensity of reutilization of nutrients as they pass downstream can be quantified in terms of the length of stream required for a nutrient atom to complete one (abstract) cycle; this distance is termed the spiralling length. The model for steady-state spiralling of a limiting nutrient predicts that most of the downstream transport of nutrient occurs in particulate or unavailable form when nutrient limitation is severe; in this case, transportability of particulates is a major determinant of spiralling length. On the other hand, when nutrient limitation is moderated by density-dependent mechanisms, transport in the dissolved phase dominates, and transportability of particles has little influence on spiralling length. The potential role of invertebrate consumers in controlling spiralling was investigated by considering their influence on regeneration, transportability, and uptake of nutrients. Functional processes of grazing and filter feeding appear most likely to shorten spiralling length when nutrient limitation is severe, while the process of shredding is more likely to shorten spiralling length when nutrient limitation is weak. In some cases there may be levels of consumer activity at which spiralling length is minimized.
