scholarly journals Crossing hydrological and geochemical modeling to understand the spatiotemporal variability of water chemistry in a headwater catchment (Strengbach, France)

2020 ◽  
Vol 24 (6) ◽  
pp. 3111-3133 ◽  
Author(s):  
Julien Ackerer ◽  
Benjamin Jeannot ◽  
Frederick Delay ◽  
Sylvain Weill ◽  
Yann Lucas ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Water Chemistry ◽  
Hydrological Model ◽  
Mean Transit Time ◽  
Spatiotemporal Variability ◽  
Flow Lines ◽  
Rock Interaction ◽  
Transit Times ◽  
Reactive Surfaces ◽  
Headwater Catchment

Abstract. Understanding the variability of the chemical composition of surface waters is a major issue for the scientific community. To date, the study of concentration–discharge relations has been intensively used to assess the spatiotemporal variability of the water chemistry at watershed scales. However, the lack of independent estimations of the water transit times within catchments limits the ability to model and predict the water chemistry with only geochemical approaches. In this study, a dimensionally reduced hydrological model coupling surface flow with subsurface flow (i.e., the Normally Integrated Hydrological Model, NIHM) has been used to constrain the distribution of the flow lines in a headwater catchment (Strengbach watershed, France). Then, hydrogeochemical simulations with the code KIRMAT (i.e., KInectic Reaction and MAss Transport) are performed to calculate the evolution of the water chemistry along the flow lines. Concentrations of dissolved silica (H4SiO4) and in basic cations (Na+, K+, Mg2+, and Ca2+) in the spring and piezometer waters are correctly reproduced with a simple integration along the flow lines. The seasonal variability of hydraulic conductivities along the slopes is a key process to understand the dynamics of flow lines and the changes of water transit times in the watershed. The covariation between flow velocities and active lengths of flow lines under changing hydrological conditions reduces the variability of water transit times and explains why transit times span much narrower variation ranges than the water discharges in the Strengbach catchment. These findings demonstrate that the general chemostatic behavior of the water chemistry is a direct consequence of the strong hydrological control of the water transit times within the catchment. Our results also show that a better knowledge of the relations between concentration and mean transit time (C–MTT relations) is an interesting new step to understand the diversity of C–Q shapes for chemical elements. The good match between the measured and modeled concentrations while respecting the water–rock interaction times provided by the hydrological simulations also shows that it is possible to capture the chemical composition of waters using simply determined reactive surfaces and experimental kinetic constants. The results of our simulations also strengthen the idea that the low surfaces calculated from the geometrical shapes of primary minerals are a good estimate of the reactive surfaces within the environment.

scholarly journals Crossing hydrological and geochemical modeling to understand the spatiotemporal variability of water chemistry in an elementary watershed (Strengbach, France)

2019 ◽  
Author(s):  
Julien Ackerer ◽  
Benjamin Jeannot ◽  
Frederick Delay ◽  
Sylvain Weill ◽  
Yann Lucas ◽  
...  
Keyword(s):  
Chemical Composition ◽  
Water Chemistry ◽  
Surface Waters ◽  
Hydrological Model ◽  
Kinetic Constants ◽  
Spatiotemporal Variability ◽  
Flow Lines ◽  
Hydrogeochemical Modeling ◽  
Transit Times ◽  
Reactive Surfaces

Abstract. Understanding the spatiotemporal variability of the chemical composition of surface waters is a major issue for the scientific community, especially given the prospect of significant environmental changes for the next decades. To date, the study of concentration-discharge relationships has been intensively used to assess the spatiotemporal variability of the water chemistry at watershed scales; however, the lack of independent estimations of the water transit times within catchments limits our ability to model and predict the water chemistry with only geochemical approaches. This study demonstrates the potential of coupling mathematical hydrology with hydrogeochemical modeling to better understand the spatiotemporal variability of the composition of surface waters. In a first step, a dimensionally reduced hydrological model coupling surface flow with subsurface flow (i.e., the Normally Integrated Hydrological Model, NIHM) has been used to constrain the distribution of the flow lines that are feeding the springs. In a second step, hydrogeochemical simulations with the code KIRMAT (KInectic Reaction and MAss Transport) have been performed to calculate the evolution of the water chemistry along the flow lines. The results indicate that the concentrations of dissolved silica (H4SiO4) and in basic cations (Na+, K+, Mg2+, and Ca2+) in the spring waters are correctly reproduced with a simple integration along the flow lines. The results also show that the modest variabilities of the flow line distribution and of the flow velocity imply that the water transit times only vary from approximately 1.5 to 3 months from floods to drought events. These findings demonstrate that the chemostatic behavior of the spring chemistry is a direct consequence of the strong hydrological control of the water transit times within the catchment. The good matching between the measured and modeled concentrations while respecting the water-rock interaction times provided by the hydrological simulations also shows that it is possible to capture the chemical composition of waters using simply determined reactive surfaces and standard kinetic constants. The results of our simulation strengthen the idea that the low surfaces calculated from the geometrical shapes of minerals are a good estimate of the reactive surfaces within the natural environment and certainly the one to be used for hydrogeochemical modeling such as that performed in this work, in addition to the use of the experimental kinetic constants for mineral dissolution. Overall, this work shows that the hydrogeochemical functioning of an elementary watershed, such as the Strengbach catchment, is relatively simple. The acquisition and variability of the water chemistry can be explained through process-based modeling approaches and by only formulating few hypotheses on the functioning of the watershed.

scholarly journals Water Quality and Hydrogeochemical Characteristics of Some Karst Water Sources in Apuseni Mountains, Romania

Water ◽  
2021 ◽  
Vol 13 (6) ◽  
pp. 857
Author(s):  
Maria-Alexandra Hoaghia ◽  
Ana Moldovan ◽  
Eniko Kovacs ◽  
Ionut Cornel Mirea ◽  
Marius Kenesz ◽  
...  
Keyword(s):  
Drinking Water ◽  
Water Chemistry ◽  
Major Ions ◽  
Anthropogenic Activities ◽  
Water Sources ◽  
Main Process ◽  
Karst Water ◽  
Rock Interaction ◽  
Apuseni Mountains ◽  
Karst Waters

Human activities and natural factors determine the hydrogeochemical characteristics of karst groundwaters and their use as drinking water. This study assesses the hydrogeochemical characteristics of 14 karst water sources in the Apuseni Mountains (NW Romania) and their potential use as drinking water sources. As shown by the Durov and by the Piper diagrams, the chemical composition of the waters is typical of karst waters as it is dominated by HCO3− and Ca2+, having a circumneutral to alkaline pH and total dissolved solids ranging between 131 and 1092 mg L−1. The relation between the major ions revealed that dissolution is the main process contributing to the water chemistry. Limestone and dolostone are the main Ca and Mg sources, while halite is the main Na and Cl source. The Gibbs diagram confirmed the rock dominance of the water chemistry. The groundwater quality index (GWQI) showed that the waters are of excellent quality, except for two waters that displayed medium and good quality status. The quality of the studied karst waters is influenced by the geological characteristics, mainly by the water–rock interaction and, to a more limited extent, by anthropogenic activities. The investigated karst waters could be exploited as drinking water resources in the study area. The results of the present study highlight the importance of karst waters in the context of good-quality water shortage but also the vulnerability of this resource to anthropogenic influences.

scholarly journals Water–rock interaction and the concentrations of major, trace, and rare earth elements in hydrocarbon-associated produced waters of the United States

2021 ◽  
Author(s):  
Carleton R. Bern ◽  
Justin E. Birdwell ◽  
Aaron M. Jubb
Keyword(s):  
United States ◽  
Rare Earth ◽  
Rare Earth Elements ◽  
Water Chemistry ◽  
Produced Water ◽  
The United States ◽  
Rock Interaction ◽  
Produced Waters ◽  
Water Rock Interaction

Comparisons of hydrocarbon-produced waters from multiple basins and experiments using multiple shales illustrate water–rock interaction influence on produced water chemistry.

Stepwise improvement of hydrological models using satellite-based evaporation and total water storage estimations

2021 ◽  
Author(s):  
Markus Hrachowitz ◽  
Petra Hulsman ◽  
Hubert Savenije
Keyword(s):  
Model Calibration ◽  
Hydrological Model ◽  
Model Development ◽  
Water Storage ◽  
Spatiotemporal Variability ◽  
Model Structure ◽  
Hydrological Models ◽  
Total Water ◽  
Spatiotemporal Model ◽  
Multiple Variables

<p>Hydrological models are often calibrated with respect to flow observations at the basin outlet. As a result, flow predictions may seem reliable but this is not necessarily the case for the spatiotemporal variability of system-internal processes, especially in large river basins. Satellite observations contain valuable information not only for poorly gauged basins with limited ground observations and spatiotemporal model calibration, but also for stepwise model development. This study explored the value of satellite observations to improve our understanding of hydrological processes through stepwise model structure adaption and to calibrate models both temporally and spatially. More specifically, satellite-based evaporation and total water storage anomaly observations were used to diagnose model deficiencies and to subsequently improve the hydrological model structure and the selection of feasible parameter sets. A distributed, process based hydrological model was developed for the Luangwa river basin in Zambia and calibrated with respect to discharge as benchmark. This model was modified stepwise by testing five alternative hypotheses related to the process of upwelling groundwater in wetlands, which was assumed to be negligible in the benchmark model, and the spatial discretization of the groundwater reservoir. Each model hypothesis was calibrated with respect to 1) discharge and 2) multiple variables simultaneously including discharge and the spatiotemporal variability in the evaporation and total water storage anomalies. The benchmark model calibrated with respect to discharge reproduced this variable well, as also the basin-averaged evaporation and total water storage anomalies. However, the evaporation in wetland dominated areas and the spatial variability in the evaporation and total water storage anomalies were poorly modelled. The model improved the most when introducing upwelling groundwater flow from a distributed groundwater reservoir and calibrating it with respect to multiple variables simultaneously. This study showed satellite-based evaporation and total water storage anomaly observations provide valuable information for improved understanding of hydrological processes through stepwise model development and spatiotemporal model calibration.</p>

Reabsorption kinetics of albumin from pleural space of dogs

1988 ◽  
Vol 255 (2) ◽  
pp. H375-H385 ◽  
Author(s):  
M. Miniati ◽  
J. C. Parker ◽  
M. Pistolesi ◽  
J. T. Cartledge ◽  
D. J. Martin ◽  
...  
Keyword(s):  
Control Mechanism ◽  
Mean Transit Time ◽  
Input Function ◽  
Pleural Space ◽  
Frequency Function ◽  
Liquid Pressure ◽  
Physiological Conditions ◽  
Transit Times ◽  
The Mean ◽  
Kinetics Of

The reabsorption of albumin from the pleural space was measured in eight dogs receiving 0.5 ml intrapleural injection of 131I-labeled albumin and a simultaneous intravenous injection of 125I-labeled albumin. Plasma curves for both tracers were obtained over 24 h. The 125I-albumin curve served as input function of albumin for interstitial spaces, including pleura, whereas the 131I-albumin curve represented the output function from pleural space. The frequency function of albumin transit times from pleural space to plasma was obtained by deconvolution of input-output plasma curves. Plasma recovery of 131I-albumin was complete by 24 h, and the mean transit time from pleura to plasma averaged 7.95 +/- 1.57 (SD) h. Albumin reabsorption occurred mainly via lymphatics as indicated by experiments in 16 additional dogs in which their right lymph ducts or thoracic ducts were ligated before intrapleural injection. A pleural lymph flow of 0.020 +/- 0.003 (SD) ml.kg-1.h-1 was estimated, which is balanced by a comparable filtration of fluid into the pleural space. This suggests that, under physiological conditions, the subpleural lymphatics represent an important control mechanism of pleural liquid pressure.

Impulse-response function of splanchnic circulation with model-independent constraints: theory and experimental validation

2003 ◽  
Vol 285 (4) ◽  
pp. G671-G680 ◽  
Author(s):  
Ole L. Munk ◽  
Susanne Keiding ◽  
Ludvik Bass
Keyword(s):  
Portal Vein ◽  
Impulse Response ◽  
Response Function ◽  
Mean Transit Time ◽  
Impulse Response Function ◽  
Parameter Estimates ◽  
Time Activity ◽  
Time Activity Curve ◽  
Transit Times ◽  
Activity Curve

Modeling physiological processes using tracer kinetic methods requires knowledge of the time course of the tracer concentration in blood supplying the organ. For liver studies, however, inaccessibility of the portal vein makes direct measurement of the hepatic dual-input function impossible in humans. We want to develop a method to predict the portal venous time-activity curve from measurements of an arterial time-activity curve. An impulse-response function based on a continuous distribution of washout constants is developed and validated for the gut. Experiments with simultaneous blood sampling in aorta and portal vein were made in 13 anesthetized pigs following inhalation of intravascular [15O]CO or injections of diffusible 3- O-[11C]methylglucose (MG). The parameters of the impulse-response function have a physiological interpretation in terms of the distribution of washout constants and are mathematically equivalent to the mean transit time ( T̄) and standard deviation of transit times. The results include estimates of mean transit times from the aorta to the portal vein in pigs: T̄ = 0.35 ± 0.05 min for CO and 1.7 ± 0.1 min for MG. The prediction of the portal venous time-activity curve benefits from constraining the regression fits by parameters estimated independently. This is strong evidence for the physiological relevance of the impulse-response function, which includes asymptotically, and thereby justifies kinetically, a useful and simple power law. Similarity between our parameter estimates in pigs and parameter estimates in normal humans suggests that the proposed model can be adapted for use in humans.

scholarly journals Diagnostic calibration of a hydrological model in an alpine area

2014 ◽  
Vol 11 (1) ◽  
pp. 1253-1300 ◽  
Author(s):  
Z. He ◽  
F. Tian ◽  
H. C. Hu ◽  
H. V. Gupta ◽  
H. P. Hu
Keyword(s):  
Hydrological Modeling ◽  
Hydrological Model ◽  
Generation Mechanism ◽  
Spatiotemporal Variability ◽  
Model Parameters ◽  
Distributed Hydrological Model ◽  
Runoff Generation ◽  
Alpine Area ◽  
Long Time ◽  
Tailan River Basin

Abstract. Hydrological modeling depends on single- or multiple-objective strategies for parameter calibration using long time sequences of observed streamflow. Here, we demonstrate a diagnostic approach to the calibration of a hydrological model of an alpine area in which we partition the hydrograph based on the dominant runoff generation mechanism (groundwater baseflow, glacier melt, snowmelt, and direct runoff). The partitioning reflects the spatiotemporal variability in snowpack, glaciers, and temperature. Model parameters are grouped by runoff generation mechanism, and each group is calibrated separately via a stepwise approach. This strategy helps to reduce the problem of equifinality and, hence, model uncertainty. We demonstrate the method for the Tailan River basin (1324 km2) in the Tianshan Mountains of China with the help of a semi-distributed hydrological model (THREW).

scholarly journals THE ROLE OF SUBSURFACE FLOW DYNAMIC ON SPATIAL AND TEMPORAL VARIATION OF WATER CHEMISTRY IN A HEADWATER CATCHMENT

2016 ◽  
Vol 8 (1) ◽  
pp. 17
Author(s):  
Tadashi Tanaka
Keyword(s):  
Water Chemistry ◽  
Temporal Variation ◽  
Random Process ◽  
Riparian Zone ◽  
Subsurface Flow ◽  
Solute Concentration ◽  
Spatial And Temporal Variation ◽  
Flow Dynamic ◽  
Headwater Catchment

Variation of water chemistry does not merely occur due to in situ chemical process, but also transport process. The study was carried out to address the role of subsurface flow dynamic on spatial and temporal variation of water chemistry in a headwater catchment. Hydrometric and hydrochemistry measurements were done in transect with nested piezometers, tensiometers, and suction samplers at different depths across hillslope and riparian zone in a 5.2 ha first-order drainage of the Kawakami experimental basin, Nagano, Central Japan from August 2000 to August 2001. Spatial variation of solute concentration was defined by the standard deviation and coefficient of variation of the seasonal observed concentrations. Autocorrelation analysis was performed to define temporal variation of solute concentration. The results showed that spatial variation of water chemistry was mainly influenced by the variation of subsurface flow through the hillslope and riparian zone. Solute concentration in the deep riparian groundwater was almost three times higher than that in the hillslope segment. A prominent downward flow in deep riparian groundwater zone provided transport of solutes to the deeper layer. Time series analysis showed that in the deep riparian groundwater, Ca2+, Mg2+, SO42- and HCO3- concentrations underwent a random process, Na+ concentration of a random process superimposed by a trend process, and SiO2 of a random process superimposed by a periodic process. Near the riparian surface, SO42- concentration was composed of a random process superimposed by a periodic process, whereas other solutes were mainly in a random process. In the hillslope soil water, there was no trend observed for the Na+ concentration, but there were for Ca2+ and Mg2+. The magnitude and direction of subsurface flow across hillslope and riparian zone created transport and deposition processes that changed solute concentration spatially and temporally.

scholarly journals Aggregation in environmental systems: seasonal tracer cycles quantify young water fractions, but not mean transit times, in spatially heterogeneous catchments

2015 ◽  
Vol 12 (3) ◽  
pp. 3059-3103 ◽  
Author(s):  
J. W. Kirchner
Keyword(s):  
Transit Time ◽  
Mean Transit Time ◽  
Strong Nonlinearity ◽  
Isotopic Tracers ◽  
Water Fraction ◽  
Benchmark Tests ◽  
Environmental Systems ◽  
Transit Times ◽  
Event Based ◽  
The Relationship

Abstract. Environmental heterogeneity is ubiquitous, but environmental systems are often analyzed as if they were homogeneous instead, resulting in aggregation errors that are rarely explored and almost never quantified. Here I use simple benchmark tests to explore this general problem in one specific context: the use of seasonal cycles in chemical or isotopic tracers (such as Cl−, δ18O, or δ2H) to estimate timescales of storage in catchments. Timescales of catchment storage are typically quantified by the mean transit time, meaning the average time that elapses between parcels of water entering as precipitation and leaving again as streamflow. Longer mean transit times imply greater damping of seasonal tracer cycles. Thus, the amplitudes of tracer cycles in precipitation and streamflow are commonly used to calculate catchment mean transit times. Here I show that these calculations will typically be wrong by several hundred percent, when applied to catchments with realistic degrees of spatial heterogeneity. This aggregation bias arises from the strong nonlinearity in the relationship between tracer cycle amplitude and mean travel time. I propose an alternative storage metric, the young water fraction in streamflow, defined as the fraction of runoff with transit times of less than roughly 0.2 years. I show that this young water fraction (not to be confused with event-based "new water" in hydrograph separations) is accurately predicted by seasonal tracer cycles within a precision of a few percent, across the entire range of mean transit times from almost zero to almost infinity. Importantly, this relationship is also virtually free from aggregation error. That is, seasonal tracer cycles also accurately predict the young water fraction in runoff from highly heterogeneous mixtures of subcatchments with strongly contrasting transit time distributions. Thus, although tracer cycle amplitudes yield biased and unreliable estimates of catchment mean travel times in heterogeneous catchments, they can be used reliably to estimate the fraction of young water in runoff.

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