HS3.5 | Advances in Diagnostics, Inversion, Sensitivity, Uncertainty Analysis, and Hypothesis Testing of Earth and Environmental Systems Models
Advances in Diagnostics, Inversion, Sensitivity, Uncertainty Analysis, and Hypothesis Testing of Earth and Environmental Systems Models
Co-organized by ESSI1/NP5
Convener: Juliane Mai | Co-conveners: Cristina PrietoECSECS, Hoshin Gupta, Uwe Ehret, Thomas Wöhling, Anneli Guthke, Wolfgang Nowak, Tobias Karl David WeberECSECS
| Tue, 25 Apr, 08:30–10:15 (CEST)
Room 3.29/30
Posters on site
| Attendance Tue, 25 Apr, 10:45–12:30 (CEST)
Hall A
Posters virtual
| Attendance Tue, 25 Apr, 10:45–12:30 (CEST)
vHall HS
Orals |
Tue, 08:30
Tue, 10:45
Tue, 10:45
Proper characterization of uncertainty remains a major research and operational challenge in Environmental Sciences, and is inherent to many aspects of modelling impacting model structure development; parameter estimation; an adequate representation of the data (inputs data and data used to evaluate the models); initial and boundary conditions; and hypothesis testing. To address this challenge, methods for a) uncertainty analysis (UA) that seek to identify, quantify and reduce the different sources of uncertainty, as well as propagating them through a system/model, and b) the closely-related methods for sensitivity analysis (SA) that evaluate the role and significance of uncertain factors (in the functioning of systems/models), have proved to be very helpful.

This session invites contributions that discuss advances, both in theory and/or application, in methods for SA/UA applicable to all Earth and Environmental Systems Models (EESMs), which embraces all areas of hydrology, such as classical hydrology, subsurface hydrology and soil science.

Topics of interest include (but are not limited to):
1) Novel methods for effective characterization of sensitivity and uncertainty
2) Analyses of over-parameterised models enabled by AI/ML techniques
3) Single- versus multi-criteria SA/UA
4) Novel approaches for parameter estimation, data inversion and data assimilation
5) Novel methods for spatial and temporal evaluation/analysis of models
6) The role of information and error on SA/UA (e.g., input/output data error, model structure error, parametric error, regionalization error in environments with no data etc.)
7) The role of SA in evaluating model consistency and reliability
8) Novel approaches and benchmarking efforts for parameter estimation
9) Improving the computational efficiency of SA/UA (efficient sampling, surrogate modelling, parallel computing, model pre-emption, model ensembles, etc.)

Orals: Tue, 25 Apr | Room 3.29/30

Chairpersons: Juliane Mai, Thomas Wöhling, Cristina Prieto
On-site presentation
Jesús Carrera and Jordi Petchamé

Numerous methods exist to gain insight on a model performance. Sensitivity analysis (SA) tools provide information on how a model output depends on model parameters. It is widely argued that SA is an essential tool for assessing model uncertainty. Here, I review global SA using Variogram Analysis of Response Surfaces (VARS), variance-based methods (Sobol' indices) and polynomial chaos expansion. For the comparison, we use a set of denitrification models, which are needed to assess the fate of nitrate, a global challenge. For each of the models, we assess the uncertainty and reliability of predictions, and the use of SA tools in designing experiments to reduce model uncertainty.

How to cite: Carrera, J. and Petchamé, J.: A comparison of sensitivity analysis methods and their value for comparing denitrification models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13589, https://doi.org/10.5194/egusphere-egu23-13589, 2023.

On-site presentation
Björn Guse, Anna Herzog, Stephan Thober, Diana Spieler, Lieke Melsen, Jens Kiesel, Maria Staudinger, Paul Wagner, Ralf Loritz, Sebastian Müller, Michael Stölzle, Larissa Scholz, Justine Berg, Tobias Pilz, Uwe Ehret, Doris Düthmann, Tobias Houska, Sandra Pool, and Larisa Tarasova and the other members of the DFG Scientific network IMPRO

Temporal sensitivity analyses can be used to detect dominant model parameters at different time steps (e.g. daily or monthly) providing insights on their temporal patterns and reflecting the temporal variability in dominant hydrological processes. However, hydrological processes do not only vary in time under different hydrometeorological conditions, but also the time scales of implemented processes are different. Here, the impact of different time scales (e.g. daily vs. monthly) on sensitivity patterns is investigated.

A temporal parameter sensitivity analysis is applied to three hydrological models (HBV, mHM and SWAT) for nine catchments in Germany. These catchments represent the variability of landscapes in Germany and are dominated by different runoff generation processes. In addition to discharge, further model fluxes and states such as evapotranspiration or soil moisture are used as target variables for the sensitivity analysis.

To analyse the impact of different time scales, two approaches are compared. In a first approach, daily simulated time series are used for the sensitivity analysis and aggregated then to monthly averaged sensitivities (Post-Agg). In a second approach, the simulated time series is first aggregated to a monthly time series and than used as input for the sensitivity analysis (Pre-Agg).

Our analysis shows that monthly averaged sensitivity patterns of different model outputs vary between Post- and Pre-Aggregation approach. Model parameters that are related to fast-reacting runoff processes, e.g. surface runoff or fast subsurface flow, are more sensitive when using daily time series for the sensitivity analysis (Post-Agg). In contrast, model parameters related processes with longer time scales such as snowmelt or evapotranspiration are more emphasized in monthly time series (Pre-Agg). These differences in the sensitivity results between Post-Agg and Pre-Agg are in particularly pronounced when using the integrated value of discharge as the target variable. Instead, the differences are smaller when applying the sensitivity analysis directly to represent model fluxes.

Moreover, our analysis shows changes in dominant parameters along a north-south gradient which can be explained by the physiographic characteristics of the catchments. The differences in the sensitivity results between the models can be related to the different model structures.

Based on our analysis, we recommend to either using model outputs of the major hydrological variables or different time scales for the sensitivity analysis to derive the maximum information from the diagnostic model analysis and to understand how model parameters describe hydrological systems.

How to cite: Guse, B., Herzog, A., Thober, S., Spieler, D., Melsen, L., Kiesel, J., Staudinger, M., Wagner, P., Loritz, R., Müller, S., Stölzle, M., Scholz, L., Berg, J., Pilz, T., Ehret, U., Düthmann, D., Houska, T., Pool, S., and Tarasova, L. and the other members of the DFG Scientific network IMPRO: Time-varying sensitivity analysis across different hydrological model structures, variables and time scales, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-8423, https://doi.org/10.5194/egusphere-egu23-8423, 2023.

On-site presentation
Yadu Pokhrel, Ahmed Elkouk, Lifeng Luo, Liz Payton, Ben Livneh, and Yifan Cheng

Understanding how land surface models (LSMs) partition precipitation into evapotranspiration and runoff under changing climate is key to improved future hydrologic predictions. This sensitivity is rarely tuned in land models, as evidenced by prevalent biases in the sensitivity of simulated runoff to precipitation and temperature change compared to observational estimates. Here, using the Community Land Model (CLM5) over the Colorado River basin (CRB), we investigate what the informative model parameters for runoff sensitivities are and how their choices affect the sensitivities under changing temperature and precipitation. We focus on the headwater region of the CRB, motivated by inconsistent model estimates of runoff sensitivities in the region and the critical need to better understand runoff changes to address the ongoing water crises in the CRB. In each headwater basin, a set of informative parameters were identified through parameter perturbations using “one at a time” method within an adaptive surrogate-based model optimization scheme (ASMO). Results of perturbations highlight that different parameter sets with similar performance (with respect to water-year discharge) provide very different runoff sensitivities to temperature and precipitation during the 1951-2010 period. Additionally, both precipitation and temperature sensitivities of runoff show sensitivity to similar parameters across the region. The most sensitive parameters control the conductance-photosynthesis relationship, soil surface resistance for direct evaporation, the partitioning of runoff into the surface and the subsurface component, and soil hydraulic properties. We show how the importance of each parameter varies through the parameter space and derive parameter estimates by maximizing the “fit to observed sensitivities” within the ASMO scheme. Our results provide key insights regarding parameters optimization to improve long-term hydrologic sensitivities in LSMs.

How to cite: Pokhrel, Y., Elkouk, A., Luo, L., Payton, L., Livneh, B., and Cheng, Y.: Impact of Model Parameters on Runoff Sensitivities in the Community Land Model: A Study on the Upper Colorado River Basin, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10644, https://doi.org/10.5194/egusphere-egu23-10644, 2023.

On-site presentation
Etienne Gaborit, Daniel Princz, Juliane Mai, Hongren Shen, Bryan Tolson, and Vincent Fortin

As part of the Great-Lakes Runoff Inter-comparison Project (GRIP-GL; Mai et al., 2022), which aims at comparing the performances of different hydrologic models over the Great-Lakes when calibrating them using the same meteorological inputs and geophysical databases, the GEM-Hydro hydrologic model used at Environment and Climate Change Canada (ECCC) to perform operational hydrologic forecasts was calibrated using different strategies. Following the calibration work related to GRIP-GL, progress has been achieved with regard to improving the calibration of the GEM-Hydro model.

The work presented here focuses on improvements achieved with regard to calibrating the GEM-Hydro model, compared to the default version of the model and to the performances obtained during the GRIP-GL project. For various reasons explained, the GEM-Hydro calibration performed as part of GRIP-GL was suboptimal. The general calibration framework remains the same as in GRIP-GL, for example by using the MESH-SVS-Raven model to speed-up simulation times and transferring the calibrated parameters into GEM-Hydro afterwards, by relying on global calibrations for each of the 6 Great-Lakes subdomains, etc. However, several important changes have been made compared to the work performed in GRIP-GL, like a new approach to represent the effect of Tile Drains, changing the set of flow stations used for calibration, revising the objective function, etc.

The proposed calibration methodology updates significantly improve GEM-Hydro streamflow performance across the Great-Lakes domain and in addition also improve or maintain similar performance levels as the default version of the model, with respect to auxiliary variables and surface fluxes: snow, soil moisture, evapotranspiration, 2m air temperature and dew point. Indeed, the model relies on 40m atmospheric forcings for wind speed, temperature and humidity, and simulates its own 2m atmospheric variables. To achieve this, it was necessary to constrain some parameter interval values during calibration, in order to prevent the calibration algorithm to choose physically-irrelevant parameter values that could allow to improve streamflow performances while degrading other hydrologic variables, due to equifinality.


Mai, J., Shen, H., Tolson, B. A., Gaborit, E., Arsenault, R., Craig, J. R., Fortin, V., Fry, L. M., Gauch, M., Klotz, D., Kratzert, F., O'Brien, N., Princz, D. G., Rasiya Koya, S., Roy, T., Seglenieks, F., Shrestha, N. K., Temgoua, A. G. T., Vionnet, V., and Waddell, J. W. (2022). The Great Lakes Runoff Intercomparison Project Phase 4: The Great Lakes (GRIP-GL). Hydrol. Earth Syst. Sci., 26, 3537–3572. Highlight paper. Accepted Jun 10, 2022.  https://doi.org/10.5194/hess-26-3537-2022

How to cite: Gaborit, E., Princz, D., Mai, J., Shen, H., Tolson, B., and Fortin, V.: On the elaboration of a robust calibration strategy for the large-scale GEM-Hydro model, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-6986, https://doi.org/10.5194/egusphere-egu23-6986, 2023.

On-site presentation
Jefferson S. Wong, Fuad Yassin, and James S. Famiglietti

Due to the lack of accurate representation of hydrological processes and parameter measurements, physically-based hydrological models consist of many parameters requiring calibration to historical observations so that reliable hydrological inference can be obtained. With the increasing data availability from various sources (e.g., satellite remote sensing, climate model reanalysis), additional information on different water balance components (e.g., soil moisture, groundwater storage, etc.) are used to constrain and validate hydrological models, resulting in better model performance and parameter identifiability. However, given the emergence of multiple datasets for various water budget components, and their differences in temporal and spatial resolutions, the uncertainties in these datasets, when used together in driving and evaluating hydrological models, could introduce potential inconsistencies in water balance estimation and lead to a non-closure problem, which could result in potentially biased parameter and water balance component estimates in hydrological modelling.

This study addresses this issue by examining the impact of inconsistent water balance component data on model performance and exploring the importance of hydrologically consistent data for robust hydrological inference. The assessment is done using a Canadian Hydrologic-Land Surface Models named MESH in the Saskatchewan River basin, Canada over the period of 2002 to 2016. Seven precipitation datasets, seven evapotranspiration products, one source of water storage data – GRACE from three different centers using spherical harmonic and mass concentration approaches – and observed discharge data from hydrometric stations are selected as the input and evaluation data. A reference water balance dataset is developed to optimally combine all available data sources for each water balance component and to obtain water balance closure though a constrained Kalman filter data assimilation technique. The MESH model is rerun with this reference dataset and results are assessed and compared to different combinations of input and evaluation data. Preliminary results reveal great variations of model performance in the water balance components when using different combinations of input and evaluation data and results of using the reference dataset is expected to have less biased water balance component estimates. This study aims to highlight the necessity of using a set of hydrologically consistent data before any model runs and model evaluation.

How to cite: Wong, J. S., Yassin, F., and Famiglietti, J. S.: Does hydrologically consistent data improve model performance? The importance of closing the water balance of input and evaluation data, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16924, https://doi.org/10.5194/egusphere-egu23-16924, 2023.

On-site presentation
Timo Houben, Mariaines Di-Dato, Christian Siebert, Thomas Kalbacher, Thomas Fischer, and Sabine Attinger

Groundwater resources are heavily exploited to supply domestic, industrial and agricultural water consumption. Climate and societal changes and associated higher abstraction will alter the subsurface storage in terms of quantity and quality in currently unpredictable ways. In order to ensure sustainable groundwater management, we must evaluate the intrinsic and spatially variable vulnerability of aquifers in terms of water quality issues and the resilience of groundwater volumes to external perturbations such as severe droughts in connection with intensive irrigation. For this purpose, physically based numerical groundwater models are of great importance, especially on the regional scale. The equations applied in these models must be fed with the hydrogeological parameters: The transmissivity T and the storativity S.

Both parameters are typically obtained through time consuming and cost intensive hydrogeological in-situ tests or by laboratory analysis of core samples from point information (drillings and wells), resulting in parameters with limited transferability to regional settings. Instead, we propose to determine the parameters by spectral analysis of groundwater level fluctuations using (semi-)analytical solutions for the frequency domain. We developed a fully automatized workflow, taking groundwater level and recharge time series together with little information about the geometry of the aquifer to derive T and S as well as tc (the characteristic response time). While the first two will be used for hydrogeological modelling, the latter can serve as an indication to assess the resilience of the groundwater system directly without additional modelling attempts. The methodology was tested with great success in simplified numerical environments and was applied to real groundwater time series in southern Germany. The response times and the storativities could be robustly estimated while the transmissivities inherit quantifiable uncertainties. Depending on the hydrogeological regime, the parameters represented effective and regional estimates.

How to cite: Houben, T., Di-Dato, M., Siebert, C., Kalbacher, T., Fischer, T., and Attinger, S.: Spectral analysis of groundwater level time series reveals hydrogeological parameters, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5635, https://doi.org/10.5194/egusphere-egu23-5635, 2023.

On-site presentation
Saket Pande and Mehdi Moayeri

The applications of statistical learning theory (SLT) in hydrology have been either in the form of Support Vector Machines and other complexity regularized machine learning algorithms that learn and predict input-output patterns such as rainfall-runoff time series or of identifying optimal complexity of low order models such as k nearest neighbour models to predict hydrological time series such as streamflow. The regularization of model complexity offers a way to identify minimal complexity of a model to accurately predict a time series of interest. However such applications often assume that the modelled residual are independent of each other. This limits its application to conceptual hydrological models where residuals are often auto-correlated. This paper applies recent results of risk bounds for time series forecasting and SLT approaches to dynamical system identification to conceptual hydrological models, offering a means to identify optimal complexity of conceptual models and complexity regularised streamflow predictions based on it.

Basins from CAMELS data set are used to demonstrate the effect of regularizing the problem of hydrological model calibration on streamflow prediction over unseen data. SAC-SMA and SIXPAR (a lower order version of SACSMA) are used as model examples. Preliminary results show that prediction uncertainty bounds are narrower if regularization does not improve the performance of a calibrated model over unseen data. This effect is stronger in drier basins than in humid ones. Also, as expected, this effect is stronger when training data size is small and holds for both SACSMA and SIXPAR. 

How to cite: Pande, S. and Moayeri, M.: Complexity-based robust hydrologic prediction: extension of statistical learning theory to conceptual hydrological models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-16039, https://doi.org/10.5194/egusphere-egu23-16039, 2023.

On-site presentation
Hossein Kavianihamedani, Julianne Quinn, and Jared Smith


Hydrologic models often are used to estimate streamflows at ungauged locations for infrastructure planning. These models can contain a multitude of parameters that themselves need to be estimated through calibration. Yet multiple sets of parameter values may perform nearly equally well in simulating flows at gauged sites, making these parameters highly uncertain. Markov Chain Monte Carlo (MCMC) algorithms can quantify parameter uncertainties; however, this can be computationally expensive for hydrological models. Thus, it is important to select an MCMC algorithm that is effective (converges to the true posterior parameter distribution), efficient (fast), reliable (consistent across random seeds) and controllable (insensitive to the algorithms hyperparameters). These characteristics can be assessed through algorithm diagnostics, but current MCMC diagnostics mostly focus on evaluating convergence of an individual search process, not diagnosing general problems of the algorithms. Therefore, additional diagnostics are required to represent algorithms sensitivity to their hyperparameters and to compare their performance across problems.

Here, we propose new diagnostics to assess the effectiveness, efficiency, reliability and controllability of four MCMC algorithms: Adaptive Metropolis, Sequential Monte Carlo, Hamiltonian Monte Carlo, and DREAM(ZS). The diagnostic method builds off of diagnostics used to assess the performance of Multi-Objective Evolutionary Algorithms (MOEAs), and allows us to evaluate the sensitivity of the algorithms to their hyper-parameterization and compare their performance on multiple metrics, such as the Gelman-Rubin diagnostic and Wasserstein distance from the true posterior. We illustrate our diagnostics using the simple Hydrological Model (HYMOD) and several analytical test problems. This allows us to see which algorithms perform well on problems with different characteristics (e.g. known vs. unknown posterior shapes, uni- vs. multi-modality, low- vs. high-dimensionality). Since posterior shapes and modality are often unknown for hydrological problems, it is important to calibrate them with an MCMC algorithm that is robust across a wide variety of posterior shapes, and our new diagnostics allow for this identification.

How to cite: Kavianihamedani, H., Quinn, J., and Smith, J.: New Diagnostic Assessment of MCMC Algorithms Effectiveness, Efficiency, Reliability, and Controllability in Calibrating Hydrological Models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10326, https://doi.org/10.5194/egusphere-egu23-10326, 2023.

On-site presentation
Giuseppe Brunetti, Jiri Simunek, Thomas Wöhling, and Christine Stumpp

Bayesian inference has become the most popular approach to uncertainty assessment in vadose zone hydrological modeling. By combining prior information with observations and model predictions, it became popular among hydrologists as it enables them to infer parameter posterior distributions, verify model adequacy, and assess the model's predictive uncertainty. In particular, the posterior distribution is frequently the variable of interest for modelers as it describes the epistemic uncertainty of model parameters conditioned on measurements. Gradient-free Markov-Chain Monte Carlo (MCMC) ensemble samplers based on Differential Evolution (DE) or Affine Invariant (AI) strategies have been used to approximate the posterior distribution, which is frequently anisotropic and correlated in vadose zone-related problems. However, a rigorous benchmark of different MCMC algorithms to provide guidelines for their application in vadose zone hydrological model calibration is still missing. In this study, we elucidate the behavior of MCMC ensemble samplers by performing an in-depth comparison of four samplers that use AI moves or DE-based strategies to approximate the target density. Two Rosenbrock distributions, and one synthetic and one actual case study focusing on the inverse estimation of soil hydraulic parameters using HYDRUS-1D, are used to compare algorithms in different dimensions. The analysis reveals that AI-based samplers are immune to affine transformations of the target density, which instead double the autocorrelation time for DE-based samplers. This behavior is reiterated in the synthetic scenario, for which AI-based algorithms outperform DE-based strategies. However, this performance gain disappears when the number of soil parameters increases from 7 to 16, with both samplers exhibiting poor acceptance rates, which are not improved by increasing the number of chains from 50 to 200 or by mixing different strategies.

How to cite: Brunetti, G., Simunek, J., Wöhling, T., and Stumpp, C.: Pitfalls and Opportunities in the Use of Markov-Chain Monte Carlo Ensemble Samplers for Vadose Zone Model Calibration, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-11129, https://doi.org/10.5194/egusphere-egu23-11129, 2023.

On-site presentation
Hui Zou, Lucy Marshall, and Ashish Sharma

Understanding the origin of errors in model predictions is a critical element in hydrologic model calibration and uncertainty estimation. While there exist a variety of plausible error sources, only one measure of the total residual error can be ascertained when the observed response is known. Here we show that collecting extra information a priori to characterise the data error before calibration can assist in improved model calibration and uncertainty estimation. A new model calibration strategy using the satellite metadata information is proposed as a means to inform the model prior, and subsequently to decompose data error from total residual error. This approach, referred to as Bayesian ecohydrological error model (BEEM), is first examined in a synthetic setting to establish its validity, and then applied to three real catchments across Australia. Results show that 1) BEEM is valid in a synthetic setting, as it can perfectly ascertain the true underlying error; 2) in real catchments the model error is reduced when utilizing the observation error variance as added error contributing to total error variance, while the magnitude of total residual error is more robust when utilizing metadata about the data quality proportionality as the basis for assigning total error variance ; 3) BEEM improves model calibration by estimating the model error appropriately and estimating the uncertainty interval more precisely. Overall, our work demonstrates a new approach to collect prior error information in satellite metadata and reveals the potential for fully utilizing metadata about error sources in uncertainty estimation.

How to cite: Zou, H., Marshall, L., and Sharma, A.: Characterising errors using satellite metadata for eco-hydrological modelling, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-5100, https://doi.org/10.5194/egusphere-egu23-5100, 2023.

Posters on site: Tue, 25 Apr, 10:45–12:30 | Hall A

Chairpersons: Juliane Mai, Thomas Wöhling, Uwe Ehret
Cristina Prieto, Le Vine Nataliya, Kavetski Dmitri, Fenicia Fabrizio, Scheidegger Andreas, and Vitolo Claudia

Modelling hydrological processes in ungauged catchments is a major challenge in environmental sciences and engineering. An ungauged catchment is a catchment that lacks streamflow data suitable for traditional modelling methods. Predicting streamflow in ungauged catchments requires some form of extrapolation ("regionalisation") from other "similar" catchments, with variables of interest being flow "indices" or "signatures", such as quantiles of the flow duration curve, etc.

Another major question in hydrology is the estimation of model structure that reflects the hydrological processes relevant to the catchment of interest. This question is intimately tied to process representation. To paraphrase a common saying, all models are wrong, but some model mechanisms (process representations) might be useful. Our previous study contributed a Bayesian framework for the identification of individual model mechanisms from streamflow data.

In this study we extend the mechanism identification method to operate in ungauged basins based on regionalized flow indices. Candidate mechanisms and model structures are generated, and then the "dominant" (more a posterior probable) model mechanisms are identified using statistical hypothesis testing. As part of the derivation, it is assumed that the error in the regionalization of flow indices dominates the structural error of the hydrological model.

The proposed method is illustrated with real data and synthetic experiments based on 92 catchments from northern Spain, from which 16 catchments are treated as ungauged. We use 624 model structures from the flexible hydrological model framework FUSE. Flow indices are regionalised using random forest regression in principal component (PC) space; we select the first 4 leading indices in PC space. The case study set up includes an experiments using real data (where the true mechanisms are unknown) and a set of synthetic experiments with different error levels (where the “true” mechanisms are known).

Across the real and synthetic experiments, routing is usually among the most identifiable processes, whereas the least identifiable processes are percolation and unsaturated zone processes. The precision, i.e. the probability of making an identification (whether correct or not), remains stable at around 25%. In the synthetic experiments we can calculate the (conditional) reliability of the identification method, i.e. the probability that, when the method makes an identification, the true mechanism is identified. The conditional reliability varies from 60% to 95% depending on the magnitude of the combined regionalization and hydrological error. Our study contributes perspectives on hydrological mechanism identification under data-scarce conditions; we discus limitations and opportunities for improvement.


Prieto, C., N. Le Vine, D. Kavetski, F. Fenicia, A. Scheidegger, and C. Vitolo (2022) An Exploration of Bayesian Identification of Dominant Hydrological Mechanisms in Ungauged Catchments, Water Resources Research, 58(3), e2021WR030705, doi: https://doi.org/10.1029/2021WR030705.

How to cite: Prieto, C., Nataliya, L. V., Dmitri, K., Fabrizio, F., Andreas, S., and Claudia, V.: Towards identification of dominant hydrological mechanisms in ungauged catchments, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3933, https://doi.org/10.5194/egusphere-egu23-3933, 2023.

Rezgar Arabzadeh, Jonathan Romero-Cuellar, Robert Chlumsky, James Craig, and Bryan Tolson

This abstract introduces a recipe for an adaptive general likelihood function and its application in the Bayesian epistemology of model parameters and structure uncertainty. The proposed methodology focuses on a special class of likelihood function, hereinafter mentioned as adaptive general likelihood function (AGL), which require a minimum priori assumptions/knowledge about the model residuals. The goal of the AGL is to characterize the model residuals independently from the inference framework in order to avoid incorrectly posterior estimation as a result of jointly inferencing of model and error model parameters. Mathematically, AGL is structured with a mixture of gaussian distributions joined with a first order autoregressive model, account for error model shape and autocorrelation respectively. To assess the AGL application, it is benchmarked with a formal likelihood function formulated by Schoups and Vrugt (2010) and evaluated for 24 Camels basins where the blended model has been deterministically applied with success (Chlumsky et al. 2022). Both approaches are compared with the residual’s empirical distributions using various statistical tests. The model used here is a blended hydrologic model introduced by Mai et al., (2021) which is a class of hydrologic models constructed by averaging (blending) various process options at the process flux level. This blending means calibration of the model functions to identify traditionally calibrated model process parameters as well as the weights utilized to average multiple process options. The model is deployed in the Raven hydrologic framework (Craig et al., 2020) and simultaneously both processes weights and parameters were calibrated deterministically for both high flows and low flows using PADDS algorithm (Asadzadeh and Tolson, 2013). This multi-objective calibration yields a suite of sample of calibrated blended models which is then utilized for error model development and testing. The tests results indicated a statistically comparable performance for both methods for t-distributed residuals highly skewed and long-tailed residual errors which are apparent in many hydrologic model residuals. Finally, to disjoin the epistemic Bayesian inference framework from the error model parameters, an epsilon-support vector regression (eps-SVR) is deterministically trained as a surrogate model to map the structural/parametric variability to residual error model parameters. The eps-SVR calibration performance metrics indicated high quality of surrogate for training set indicating promising performance.

How to cite: Arabzadeh, R., Romero-Cuellar, J., Chlumsky, R., Craig, J., and Tolson, B.: Adaptive Surrogate Likelihood Function for Blended Hydrologic Models, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-15689, https://doi.org/10.5194/egusphere-egu23-15689, 2023.

Model validation in natural hazard forecasting requires an unambiguous hierarchy of uncertainties
Warner Marzocchi and Thomas Jordan
Zoe Li, Pengxiao Zhou, and Maysara Ghaith

There are significant uncertainties associated with the estimates of model parameters in hydrological and environmental modeling. Such uncertainties could propagate within a modeling framework, leading to considerable deviation of the predicted value from its real value. Quantifying the uncertainties associated with model parameters could be computationally exhaustive and is still a daunting challenge to hydrological and environmental engineers. In this study, a series of Polynomial Chaos Expansion (PCE) methods, which have a significant advantage in computational efficiency, is developed to assess the propagation of parameter uncertainty. The proposed approaches were applied to two hydrological/environmental modeling case studies. The uncertainty quantification results will be compared with those from the traditional Monte Carlo simulation technique, to demonstrate the effectiveness and efficiency of the proposed approaches. This work will provide an efficient and reliable alternative to assess the impacts of the parameter uncertainties in hydrological and environmental modeling.

How to cite: Li, Z., Zhou, P., and Ghaith, M.: Uncertainty Quantification in Hydrological and Environmental Modeling based on Polynomial Chaos Expansion, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10510, https://doi.org/10.5194/egusphere-egu23-10510, 2023.

Claire Lauvernet, Claudio Paniconi, Emilie Rouzies, Laura Gatel, and Antoine Caisson

In small agricultural catchments over Europe, intensive use of pesticides leads to widespread contamination of rivers and groundwater, largely due to hydraulic transfers of these reactive solutes from plots to rivers. These transfers must be better understood and described in the watershed in order to be able to propose best management practices adapted to the catchment and to reduce its contamination. The physically based model CATHY simulates interactions between surface and subsurface hydrology and reactive solute transport. However, the high sensitivity of pesticide transfers to spatially heterogeneous soil properties induces uncertainty that should be quantified and reduced. In situ data on pesticides in a catchment are usually rare and not continuous in time and space. Likewise, satellite imagery can provide spatial observations of hydrologic variables but not generally of pesticide fluxes and concentrations, and at limited scale and time frequency. The objective of this work is to combine these 3 types of information (model, in situ data, images) and their associated errors with data assimilation methods, in order to reduce pesticide and hydrological variable uncertainties. The sensitivity to spatial density and temporal frequency of the data will be evaluated, as well as the coupled data assimilation efficiency, i.e., the effect of assimilating hydrological data on pesticide-related variables. The methods will be developed using a Python package, and compared/evaluated on twin experiments using virtual data that are however generated over a real vineyard catchment, in Beaujolais, France, in order to ensure realism of the experiments, data, and associated errors.

How to cite: Lauvernet, C., Paniconi, C., Rouzies, E., Gatel, L., and Caisson, A.: Combining water and pesticide data with coupled surface/subsurface hydrological modeling to reduce its uncertainty., EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13104, https://doi.org/10.5194/egusphere-egu23-13104, 2023.

The Estimation Model of Groundwater Hydrogeological Parameters Combining Groundwater Level Signal Analysis
Tzu-Yu Yeh and Yuan-Chien Lin
Rao Ali Javed, Timo Houben, Thomas Kalbacher, and Sabine Attinger

Common in-situ methods like pumping tests, slug tests and laboratory analysis reveal aquifer parameters (that is the transmissivity and storativity) that are localized and specific to the measurement location. A need for regionally valid aquifer parameters arises when setting up regional scale physically based groundwater models. The models would help water resource managers to plan and predict the quality and quantity of groundwater resources, thus supports decision making as well as sustainable fresh water supply. A study from Houben et al. 2022 indicate that regional aquifer parameters can be obtained by analysing the frequency content of groundwater level time-series. Their work builds upon a semi-analytical solution for the groundwater head spectrum stochastically derived from the Boussinesq equation evoking the Dupuit assumptions. They found that the solution can be used to infer the transmissivity and storativity from groundwater level fluctuations and validated their hypothesis in simplified numerical environments of different complexity.

In this work, we extended the numerical experiments and applied the semi-analytical solution in homogeneous and heterogeneous 2D (x-y-plane) aquifers as well as in a complex numerical 2D (x-y-plane) model of the upper Danube catchment. We tested the hypothesis that certain locations can reveal regional aquifer parameters. In a homogeneous simulated model, the semi-analytical solution reveals effectively the model input parameters which serves as a proof-of-concept. In a heterogeneous numerical model, the obtained parameters show the complex interplay between zones of different permeability. The effects of high permeable zones can be observed on the low permeable zones which are further apart and vice versa. The obtained parameters were in the range of the model input parameters and followed the trend of the input parameters along the direction of flow. In the model of the upper Danube the obtained parameters were systematically larger than the input parameters. The shift in the obtained parameters was attributed to a violation of the assumptions of the semi-analytical solution. Thus, the complexity of model leads to a breakdown of the semi-analytical solution in some areas. Analyses on a sub-catchment scale revealed that when the assumptions of the analytical solution are met, the obtained parameters reflect the effective parameters.

How to cite: Javed, R. A., Houben, T., Kalbacher, T., and Attinger, S.: Investigating the spectral analysis of groundwater level fluctuations in a numerical model of the upper Danube catchment in Germany, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-10001, https://doi.org/10.5194/egusphere-egu23-10001, 2023.

Mariaines Di Dato, Timo Houben, and Sabine Attinger

During dry periods, river flow comprises baseflow, which typically generates from shallow aquifers. Understanding how such aquifers respond to climate events is key to managing environmental issues related to water supply or water quality. A typical indicator of groundwater response to climate events is the characteristic response time, which indicates the rate of depletion of shallow aquifers.

The traditional method to infer the characteristic response time analyzes the slope of the hydrograph recession curve. Such a method does not account for stormwater contribution in recession analysis, thereby assuming that the catchment is dry and the only contribution to discharge originates from groundwater. As a consequence, the recession analysis might underestimate the groundwater response time, owing to the presence of faster discharge components, i.e. surface runoff or interflow, in the falling limbs.

In this work, we propose an alternative methodology to calculate the characteristic response time, which is determined by analyzing the behavior of the baseflow time series in the frequency domain. The aquifer can be conceptualized as a low-pass filter, which smooths the high-fluctuating components in the recharge signal. Such behavior causes a cut-off frequency in the baseflow spectrum, which corresponds to the aquifer characteristic time. We applied this approach to several gauging stations in Germany, whose humid climate is ideal to compare the results with the classical recession analysis.

We observed that spectral analysis yields characteristic response times systematically larger than the ones calculated with recession analysis. On average there is a factor of two between the estimates provided by the two methods. Overall our study emphasizes careful consideration of the estimation of groundwater response times, especially in humid and sub-humid river basins.

How to cite: Di Dato, M., Houben, T., and Attinger, S.: Estimating groundwater response time in humid climate by using spectral analysis, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-3891, https://doi.org/10.5194/egusphere-egu23-3891, 2023.

Niels Schuetze, Corina Hauffe, Sofie Pahner, Clara Brandes, Kan Lei, and Mellentin Udo

Catchments in Saxony differ regarding their physiographic characteristics (topography, geomorphology, geology, land use, soils, etc.) and their climatic boundaries. Both factors influence the flow behavior and the water balance components of catchments. How sensitive the water balance of catchments responds to current and future changes in the climatic boundary conditions is difficult to predict for each catchment and is associated with significant uncertainties. In Saxony, the pronounced drought in groundwater and surface water from 2018 to 2020 led to considerable regional problems in water supply and quality.

Schwarze et al. (2017) already investigated trends of the observed discharge and variables derived by hydrograph separation (e.g. baseflow) in a sensitivity study. In this presentation, we show the results of an extension of this analysis with current observation data until 2020. The following research questions are investigated: (i) Are catchments in Saxony already responding to changing climatic conditions? (ii) Which regions show the most significant changes in discharge behavior relative to other water balance components? (iii) What are the factors and drivers of changes in the water balance in Saxonian Catchments?

The study is based only on observational data for precipitation, temperature, and discharge in the period of 1961 to 2020 in Saxony. Break point analysis, hydrograph separation, and sensitivity analysis of hydrological signatures are performed for different sets of climate periods to quantify changes and elasticity of the water balance components. As a result, a decreasing trend for the mean flow can be seen for almost all 88 investigated and undisturbed catchments in Saxony. This trend is more pronounced in the mountainous regions than in the lowland of Saxony. Despite the slight increase in the mean annual precipitation, the temperature rise of about one °C from 1991-2020 compared to 1961-1990 in all catchments leads to an increasing evapotranspiration, reduced discharge, and groundwater recharge.



Schwarze, R., Wagner, M. and Röhm, P. (2017). Adaptation strategies to climate change - Analysis of the sensitivity of water balance variables of Saxon gauge catchments with respect to the increased temperature level from 1988 onwards compared to the reference state of 1961-1987. Ed.: Saxon State Office for Environment, Agriculture and Geology (LfULG), 2017.

How to cite: Schuetze, N., Hauffe, C., Pahner, S., Brandes, C., Lei, K., and Udo, M.: Sensitivity analysis of water balance components under climate change in Saxony, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-13981, https://doi.org/10.5194/egusphere-egu23-13981, 2023.

Posters virtual: Tue, 25 Apr, 10:45–12:30 | vHall HS

Chairpersons: Juliane Mai, Thomas Wöhling, Wolfgang Nowak
Qinzhuo Liao

Reservoir simulations often require statistical predictions to quantify production uncertainty or assess potential risks. Most existing uncertainty quantification procedures aim to decompose the input random field into independent random variables if the correlation scale is small compared to the domain size. In this work, we develop a K-means-based aggregation model, for efficiently estimating multiphase flow performance in multiple geological realizations. This approach performs a number of single-phase flow simulations and uses K-means clustering to select only a few representatives on which multiphase flow simulations are performed. In addition, an empirical model is then employed to describe the relationship between the single-phase solution and the multiphase solution using these representatives. Finally, the multiphase solution in all realizations can be easily predicted using empirical models. The method is applicable to both 2D and 3D synthetic models and has been shown to perform well in the trusted interval of productivity, and probability distribution as indicated by the cumulative density function. It is able to capture a large number of ensemble statistical realizations of Monte Carlo simulation results with significantly reduced computational cost.

How to cite: Liao, Q.: Clustering aggregation model for statistical forecasting of multiphase flow problems, EGU General Assembly 2023, Vienna, Austria, 23–28 Apr 2023, EGU23-973, https://doi.org/10.5194/egusphere-egu23-973, 2023.