TY - JOUR A1 - Munz, Matthias A1 - Oswald, Sascha A1 - Schmidt, Christian T1 - Analysis of riverbed temperatures to determine the geometry of subsurface water flow around in-stream geomorphological structures JF - Journal of hydrology N2 - The analytical evaluation of diurnal temperature variation in riverbed sediments provides detailed information on exchange fluxes between rivers and groundwater. The underlying assumption of the stationary, one-dimensional vertical flow field is frequently violated in natural systems where subsurface water flow often has a significant horizontal component. In this paper, we present a new methodology for identifying the geometry of the subsurface flow field using vertical temperature profiles. The statistical analyses are based on model optimisation and selection and are used to evaluate the shape of vertical amplitude ratio profiles. The method was applied to multiple profiles measured around in-stream geomorphological structures in a losing reach of a gravel bed river. The predominant subsurface flow field was systematically categorised in purely vertical and horizontal (hyporheic, parafluvial) components. The results highlight that river groundwater exchange flux at the head, crest and tail of geomorphological structures significantly deviated from the one-dimensional vertical flow, due to a significant horizontal component. The geometry of the subsurface water flow depended on the position around the geomorphological structures and on the river level. The methodology presented in this paper features great potential for characterising the spatial patterns and temporal dynamics of complex subsurface flow geometries by using measured temperature time series in vertical profiles. (C) 2016 Elsevier B.V. All rights reserved. KW - Temperature time series KW - Amplitude ratio KW - River-groundwater exchange KW - Hyporheic zone KW - In-stream geomorphological structures KW - River restoration Y1 - 2016 U6 - https://doi.org/10.1016/j.jhydrol.2016.05.012 SN - 0022-1694 SN - 1879-2707 VL - 539 SP - 74 EP - 87 PB - Elsevier CY - Amsterdam ER - TY - GEN A1 - Wang, Wei-shi A1 - Oswald, Sascha A1 - Gräff, Thomas A1 - Lensing, Hermann-Josef A1 - Liu, Tie A1 - Strasser, Daniel A1 - Munz, Matthias T1 - Correction: Impact of river reconstruction on groundwater flow during bank filtration assessed by transient three-dimensional modelling of flow and heat transport. - Hydrogeology Journal. - Berlin: Springer. - 28 (2020) , S. 723. - https://doi.org/10.1007/s10040-019-02063-3 T2 - Hydrogeology journal : official journal of the International Association of Hydrogeologists T2 - Erratum: Impact de la reconstruction d’une rivière sur l’écoulement des eaux souterraines via la filtration sur berge évalué par un modèle tridimensionnel en régime transitoire de l’écoulement et du transport de chaleur. - Berlin: Springer. - 28 (2020) , S. 723. - https://doi.org/10.1007/s10040-019-02063-3 T2 - Erratum: Impacto de la restauración de un río en el flujo de agua subterránea durante la filtración en las márgenes, evaluado mediante la modelización tridimensional transitoria del flujo y el transporte de calor. - Berlin: Springer. - 28 (2020) , S. 723. - https://doi.org/10.1007/s10040-019-02063-3 Y1 - 2020 U6 - https://doi.org/10.1007/s10040-020-02221-y SN - 1431-2174 SN - 1435-0157 VL - 28 IS - 7 SP - 2633 EP - 2634 PB - Springer CY - Berlin ; Heidelberg ; New York, NY ER - TY - JOUR A1 - Munz, Matthias A1 - Oswald, Sascha A1 - Schmidt, Christian T1 - Coupled Long-Term Simulation of Reach-Scale Water and Heat Fluxes Across the River-Groundwater Interface for Retrieving Hyporheic Residence Times and Temperature Dynamics JF - Water resources research N2 - Flow patterns in conjunction with seasonal and diurnal temperature variations control ecological and biogeochemical conditions in hyporheic sediments. In particular, hyporheic temperatures have a great impact on many temperature-sensitive microbial processes. In this study, we used 3-D coupled water flow and heat transport simulations applying the HydroGeoSphere code in combination with high-resolution observations of hydraulic heads and temperatures to quantify reach-scale water and heat flux across the river-groundwater interface and hyporheic temperature dynamics of a lowland gravel bed river. The model was calibrated in order to constrain estimates of the most sensitive model parameters. The magnitude and variations of the simulated temperatures matched the observed ones, with an average mean absolute error of 0.7 degrees C and an average Nash Sutcliffe efficiency of 0.87. Our results indicate that nonsubmerged streambed structures such as gravel bars cause substantial thermal heterogeneity within the saturated sediment at the reach scale. Individual hyporheic flow path temperatures strongly depend on the flow path residence time, flow path depth, river, and groundwater temperature. Variations in individual hyporheic flow path temperatures were up to 7.9 degrees C, significantly higher than the daily average (2.8 degrees C), but still lower than the average seasonal hyporheic temperature difference (19.2 degrees C). The distribution between flow path temperatures and residence times follows a power law relationship with exponent of about 0.37. Based on this empirical relation, we further estimated the influence of hyporheic flow path residence time and temperature on oxygen consumption which was found to partly increase by up to 29% in simulations. Y1 - 2017 U6 - https://doi.org/10.1002/2017WR020667 SN - 0043-1397 SN - 1944-7973 VL - 53 SP - 8900 EP - 8924 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Munz, Matthias A1 - Schmidt, Christian T1 - Estimation of vertical water fluxes from temperature time series by the inverse numerical computer program FLUX-BOT JF - Hydrological processes N2 - The application of heat as a hydrological tracer has become a standard method for quantifying water fluxes between groundwater and surface water. The typical application is to estimate vertical water fluxes in the shallow subsurface beneath streams or lakes. For this purpose, time series of temperatures in the surface water and in the sediment are measured and evaluated by a vertical 1D representation of heat transport by advection and conduction. Several analytical solutions exist to calculate the vertical water flux from the measured temperatures. Although analytical solutions can be easily implemented, they are restricted to specific boundary conditions such as a sinusoidal upper temperature boundary. Numerical solutions offer higher flexibility in the selection of the boundary conditions. This, in turn, reduces the effort of data preprocessing, such as the extraction of the diurnal temperature variation from the raw data. Here, we present software to estimate water fluxes based on temperaturesFLUX-BOT. FLUX-BOT is a numerical code written in MATLAB that calculates vertical water fluxes in saturated sediments based on the inversion of measured temperature time series observed at multiple depths. FLUX-BOT applies a centred Crank-Nicolson implicit finite difference scheme to solve the one-dimensional heat advection-conduction equation. FLUX-BOT includes functions for the inverse numerical routines, functions for visualizing the results, and a function for performing uncertainty analysis. We present applications of FLUX-BOT to synthetic and to real temperature data to demonstrate its performance. KW - heat tracing KW - numerical solution KW - surface water groundwater interaction KW - temperature time series KW - vertical water flux Y1 - 2017 U6 - https://doi.org/10.1002/hyp.11198 SN - 0885-6087 SN - 1099-1085 VL - 31 SP - 2713 EP - 2724 PB - Wiley CY - Hoboken ER - TY - JOUR A1 - Wang, Wei-shi A1 - Oswald, Sascha A1 - Gräff, Thomas A1 - Lensing, Hermann Josef A1 - Liu, Tie A1 - Strasser, Daniel A1 - Munz, Matthias T1 - Impact of river reconstruction on groundwater flow during bank filtration assessed by transient three-dimensional modelling of flow and heat transport JF - Hydrogeology journal : official journal of the International Association of Hydrogeologists N2 - Bank filtration (BF) is an established indirect water-treatment technology. The quality of water gained via BF depends on the subsurface capture zone, the mixing ratio (river water versus ambient groundwater), spatial and temporal distribution of subsurface travel times, and subsurface temperature patterns. Surface-water infiltration into the adjacent aquifer is determined by the local hydraulic gradient and riverbed permeability, which could be altered by natural clogging, scouring and artificial decolmation processes. The seasonal behaviour of a BF system in Germany, and its development during and about 6 months after decolmation (canal reconstruction), was observed with a long-term monitoring programme. To quantify the spatial and temporal variation in the BF system, a transient flow and heat transport model was implemented and two model scenarios, 'with' and 'without' canal reconstruction, were generated. Overall, the simulated water heads and temperatures matched those observed. Increased hydraulic connection between the canal and aquifer caused by the canal reconstruction led to an increase of similar to 23% in the already high share of BF water abstracted by the nearby waterworks. Subsurface travel-time distribution substantially shifted towards shorter travel times. Flow paths with travel times <200 days increased by similar to 10% and those with <300 days by 15%. Generally, the periodic temperature signal, and the summer and winter temperature extrema, increased and penetrated deeper into the aquifer. The joint hydrological and thermal effects caused by the canal reconstruction might increase the potential of biodegradable compounds to further penetrate into the aquifer, also by potentially affecting the redox zonation in the aquifer. KW - bank filtration KW - groundwater KW - surface-water relations KW - groundwater modelling Y1 - 2019 U6 - https://doi.org/10.1007/s10040-019-02063-3 SN - 1431-2174 SN - 1435-0157 VL - 28 IS - 2 SP - 723 EP - 743 PB - Springer CY - Berlin ; Heidelberg [u.a.] ER - TY - JOUR A1 - Schreiber, Lisa A1 - Munz, Matthias A1 - Salzmann, Thomas A1 - Oswald, Sascha T1 - Coupled simulation of groundwater and drainage dynamics in a coastal fen T1 - Modellierung der Strömungsdynamik in einem revitalisierten Küstenmoorgebiet an der Ostsee JF - Grundwasser : Zeitschrift der Fachsektion Hydrogeologie in der Deutschen Gesellschaft für Geowissenschaften (FH-DGG) N2 - Coastal wetlands are characterized by continued human influence, e.g. with drainage ditches, coastal dikes or landscape restoration. In addition, it is important to understand the complex interactions with the sea to predict impacts of further development. In the present study the aim was to analyze surface and subsurface flow in a coastal wetland located at the Baltic Sea coastline near Warnemunde (Germany) to quantify water exchange with the Baltic Sea and analyze the effect of a storm flood event on saline intrusion. A 3-D transient groundwater model and a one-dimensional surface water model were set up and calibrated by using hydraulic head measurements. The results indicate that in addition to ditch flow, groundwater discharge to the Baltic Sea often has a significant influence on the overall water budget of the fen. From the transient modelling it became evident that water exchange between groundwater in the fen and the Baltic Sea depends on sea level and very often fluctuates between seaward and landward flow directions on daily to weekly time scales. N2 - Küstennahe Niedermoore wurden durch den Menschen verändert, bspw. durch das Anlegen von Entwässerungsgräben, dem Bau von Küstenschutzdeichen oder aktuell einer Renaturierung. Außerdem ist es wichtig die komplexe Interaktion mit der See zu verstehen, um Aussagen über die zukünftige Entwicklung treffen zu können. In der vorliegenden Studie wurde die ober- und unterirdische Strömung in einem Feuchtgebiet an der mecklenburgischen Ostseeküste nahe Warnemünde (Deutschland) untersucht, um dessen wechselseitigen Austausch mit der Ostsee zu quantifizieren und zu analysieren, wie sich ein Sturmhochwasserereignis auf den Salzeintrag ins Gebiet auswirkt. Hierfür wurde ein dreidimensionales instationäres Grundwassermodell erstellt, mit einem eindimensionalen Modell des Grabensystems gekoppelt und mit Messungen im Gebiet kalibriert und verglichen. Die Ergebnisse zeigen, dass neben der oberirdischen Entwässerung auch der Grundwasserabstrom in Richtung Ostsee eine wesentliche Komponente der Wasserbilanz darstellt. Das Verhalten entlang der Küste wird deutlich durch die Dynamik der Ostseewasserstände geprägt, wobei ein Grundwasserabstrom mit einem Zustrom von Ostseewasser bei hohen Küstenwasserständen innerhalb täglicher bis wöchentlicher Zeitskalen wechselt. KW - numerical modeling KW - Baltic Sea coast KW - groundwater-surface water KW - interaction KW - storm flood KW - salinization KW - Numerische Modellierung KW - Ostseeküste KW - Grundwasser-Oberflächenwasser-Interaktion KW - Sturmhochwasser KW - Versalzung Y1 - 2021 U6 - https://doi.org/10.1007/s00767-021-00486-y SN - 1430-483X SN - 1432-1165 VL - 26 IS - 3 SP - 289 EP - 304 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Munz, Matthias A1 - Krause, Stefan A1 - Tecklenburg, Christina A1 - Binley, Andrew T1 - Reducing monitoring gaps at the aquifer-river interface by modelling groundwater-surface water exchange flow patterns JF - Hydrological processes N2 - This study investigates spatial patterns and temporal dynamics of aquifer-river exchange flow at a reach of the River Leith, UK. Observations of sub-channel vertical hydraulic gradients at the field site indicate the dominance of groundwater up-welling into the river and the absence of groundwater recharge from surface water. However, observed hydraulic heads do not provide information on potential surface water infiltration into the top 0-15 cm of the streambed as these depths are not covered by the existing experimental infrastructure. In order to evaluate whether surface water infiltration is likely to occur outside the 'window of detection', i.e. the shallow streambed, a numerical groundwater model is used to simulate hydrological exchanges between the aquifer and the river. Transient simulations of the successfully validated model (Nash and Sutcliff efficiency of 0.91) suggest that surface water infiltration is marginal and that the possibility of significant volumes of surface water infiltrating into non-monitored shallow streambed sediments can be excluded for the simulation period. Furthermore, the simulation results show that with increasing head differences between river and aquifer towards the end of the simulation period, the impact of streambed topography and hydraulic conductivity on spatial patterns of exchange flow rates decreases. A set of peak flow scenarios with altered groundwater-surface water head gradients is simulated in order to quantify the potential for surface water infiltration during characteristic winter flow conditions following the observation period. The results indicate that, particularly at the beginning of peak flow conditions, head gradients are likely to cause substantial increase in surface water infiltration into the streambed. The study highlights the potential for the improvement of process understanding of hyporheic exchange flow patterns at the stream reach scale by simulating aquifer-river exchange fluxes with a standard numerical groundwater model and a simple but robust model structure and parameterization. Copyright KW - hyporheic zone KW - aquifer-river interface KW - groundwater-surface water exchange KW - MODFLOW Y1 - 2011 U6 - https://doi.org/10.1002/hyp.8080 SN - 0885-6087 VL - 25 IS - 23 SP - 3547 EP - 3562 PB - Wiley-Blackwell CY - Malden ER - TY - JOUR A1 - Munz, Matthias A1 - Oswald, Sascha A1 - Schmidt, C. T1 - Sand box experiments to evaluate the influence of subsurface temperature probe design on temperature based water flux calculation JF - Hydrology and earth system sciences : HESS N2 - Quantification of subsurface water fluxes based on the one dimensional solution to the heat transport equation depends on the accuracy of measured subsurface temperatures. The influence of temperature probe setup on the accuracy of vertical water flux calculation was systematically evaluated in this experimental study. Four temperature probe setups were installed into a sand box experiment to measure temporal highly resolved vertical temperature profiles under controlled water fluxes in the range of +/- 1.3 md(-1). Pass band filtering provided amplitude differences and phase shifts of the diurnal temperature signal varying with depth depending on water flux. Amplitude ratios of setups directly installed into the saturated sediment significantly varied with sand box hydraulic gradients. Amplitude ratios provided an accurate basis for the analytical calculation of water flow velocities, which matched measured flow velocities. Calculated flow velocities were sensitive to thermal properties of saturated sediment and to temperature sensor spacing, but insensitive to thermal dispersivity equal to solute dispersivity. Amplitude ratios of temperature probe setups indirectly installed into piezometer pipes were influenced by thermal exchange processes within the pipes and significantly varied with water flux direction only. Temperature time lags of small sensor distances of all setups were found to be insensitive to vertical water flux. Y1 - 2011 U6 - https://doi.org/10.5194/hess-15-3495-2011 SN - 1027-5606 VL - 15 IS - 11 SP - 3495 EP - 3510 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Barkow, Isolde S. A1 - Oswald, Sascha A1 - Lensing, Hermann Josef A1 - Munz, Matthias T1 - Seasonal dynamics modifies fate of oxygen, nitrate, and organic micropollutants during bank filtration BT - temperature-dependent reactive transport modeling of field data JF - Environmental science and pollution research : official organ of the EuCheMS Division for Chemistry and the Environment, EuCheMS DCE N2 - Bank filtration is considered to improve water quality through microbially mediated degradation of pollutants and is suitable for waterworks to increase their production. In particular, aquifer temperatures and oxygen supply have a great impact on many microbial processes. To investigate the temporal and spatial behavior of selected organic micropollutants during bank filtration in dependence of relevant biogeochemical conditions, we have set up a 2D reactive transport model using MODFLOW and PHT3D under the user interface ORTI3D. The considered 160-m-long transect ranges from the surface water to a groundwater extraction well of the adjacent waterworks. For this purpose, water levels, temperatures, and chemical parameters were regularly measured in the surface water and groundwater observation wells over one and a half years. To simulate the effect of seasonal temperature variations on microbial mediated degradation, we applied an empirical temperature factor, which yields a strong reduction of the degradation rate at groundwater temperatures below 11 degrees C. Except for acesulfame, the considered organic micropollutants are substantially degraded along their subsurface flow paths with maximum degradation rates in the range of 10(-6) mol L-1 s(-1). Preferential biodegradation of phenazone, diclofenac, and valsartan was found under oxic conditions, whereas carbamazepine and sulfamethoxazole were degraded under anoxic conditions. This study highlights the influence of seasonal variations in oxygen supply and temperature on the fate of organic micropollutants in surface water infiltrating into an aquifer. KW - bank filtration KW - aerobic and anaerobic conditions KW - pharmaceuticals and KW - personal care products KW - reactive transport modeling KW - degradation Y1 - 2020 U6 - https://doi.org/10.1007/s11356-020-11002-9 SN - 0944-1344 SN - 1614-7499 VL - 28 IS - 8 SP - 9682 EP - 9700 PB - Springer CY - Heidelberg ER - TY - JOUR A1 - Krause, Stefan A1 - Tecklenburg, Christina A1 - Munz, Matthias A1 - Naden, Emma T1 - Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river JF - Journal of geophysical research : Biogeosciences N2 - Biogeochemical turnover in hyporheic zones is known to have the potential to affect the chemical signature of surface water cycling through shallow streambed sediments. This study investigates the impact of streambed physical properties on the fate of nitrate and dissolved oxygen in groundwater upwelling through the streambed of a lowland river. For analyzing depth-dependent patterns and zonation of nitrogen concentrations, diffuse gel probes in shallow (top 15 cm) streambed sediments have been deployed in a nested setup together with multilevel minipiezometers for streambed sediments of 15-150 cm. Spatial heterogeneity of groundwater upwelling was controlled by patterns of low-conductivity peat and clay strata that caused locally confined conditions, suggesting increased streambed residence times. Nitrate concentrations in the upwelling groundwater changed by up to 68.06 mg L-1 within the top 15 cm of streambed sediments and by up to 107.47 mg L-1 at depths of 15-150 cm, indicating that significant nitrogen turnover was not restricted to shallow streambed sediments. Intensive reduction of nitrate concentrations was found, in particular, in vicinity of low-conductivity streambed strata. The coincidence of confined groundwater upwelling and reduced oxygen concentrations at these locations suggests that increased residence times and associated depletion of dissolved oxygen create conditions favorable for nitrate reduction. Our results highlight that increased nitrogen turnover at aquifer-river interfaces is not necessarily limited to shallow streambed zones, where surface water is mixing with groundwater, but can affect upwelling groundwater in reactive hot spots that extend to greater streambed depths and beyond hyporheic mixing zones. Citation: Krause, S., C. Tecklenburg, M. Munz, and E. Naden (2013), Streambed nitrogen cycling beyond the hyporheic zone: Flow controls on horizontal patterns and depth distribution of nitrate and dissolved oxygen in the upwelling groundwater of a lowland river, Y1 - 2013 U6 - https://doi.org/10.1029/2012JG002122 SN - 0148-0227 VL - 118 IS - 1 SP - 54 EP - 67 PB - American Geophysical Union CY - Washington ER -