On the colour and spin of epistemic error (and what we might do about it)

Abstract. In recent years, a strong debate has emerged in the hydrologic literature regarding how to properly treat nontraditional error residual distributions and quantify parameter and predictive uncertainty. Particularly, there is strong disagreement whether such uncertainty framework should have its roots within a proper statistical (Bayesian) context using Markov chain Monte Carlo (MCMC) simulation techniques, or whether such a framework should be based on a quite different philosophy and implement informal likelihood functions and simplistic search methods to summarize parameter and predictive distributions. This paper is a follow-up of our previous work published in Vrugt and Sadegh (2013) and demonstrates that approximate Bayesian computation (ABC) bridges the gap between formal and informal statistical model-data fitting approaches. The ABC methodology has recently emerged in the fields of biology and population genetics and relaxes the need for an explicit likelihood function in favor of one or multiple different summary statistics that measure the distance of each model simulation to the data. This paper further studies the theoretical and numerical equivalence of formal and informal Bayesian approaches using discharge and forcing data from different watersheds in the United States, in particular generalized likelihood uncertainty estimation (GLUE). We demonstrate that the limits of acceptability approach of GLUE is a special variant of ABC if each discharge observation of the calibration data set is used as a summary diagnostic.

Section: Case Studies: Hydrologic Modelingmentioning

confidence: 99%

Bridging the gap between GLUE and formal statistical approaches: approximate Bayesian computation

Sadegh

Vrugt

2013

“…Also, the use of regional models for solving local issues, as well as the reverse, leads to equifinality problems (Beven, 1989;Beven et al, 2011;Ebel and Loague, 2006;Klemes, 1983;Polus et al, 2011), boundary condition inconsistencies (Noto et al, 2008), or computational burdens (Jolly and Rassam, 2009). The use of local models for solving regional issues entails the same effects Gunduz, 2003, 2006;Wondzell et al, 2009).…”

Section: Up-and Downscaling Stream-aquifer Exchangesmentioning

confidence: 99%

Continental hydrosystem modelling: the concept of nested stream–aquifer interfaces

Flipo

Mouhri

Labarthe

et al. 2014

Abstract. Coupled hydrological-hydrogeological models, emphasising the importance of the stream-aquifer interface, are more and more used in hydrological sciences for pluridisciplinary studies aiming at investigating environmental issues. Based on an extensive literature review, stream-aquifer interfaces are described at five different scales: local [10 cm- . This led us to develop the concept of nested stream-aquifer interfaces, which extends the well-known vision of nested groundwater pathways towards the surface, where the mixing of low frequency processes and high frequency processes coupled with the complexity of geomorphological features and heterogeneities creates hydrological spiralling. This conceptual framework allows the identification of a hierarchical order of the multi-scale control factors of stream-aquifer hydrological exchanges, from the larger scale to the finer scale. The hyporheic corridor, which couples the river to its 3-D hyporheic zone, is then identified as the key component for scaling hydrological processes occurring at the interface. The identification of the hyporheic corridor as the support of the hydrological processes scaling is an important step for the development of regional studies, which is one of the main concerns for water practitioners and resources managers.In a second part, the modelling of the stream-aquifer interface at various scales is investigated with the help of the conductance model. Although the usage of the temperature as a tracer of the flow is a robust method for the assessment of stream-aquifer exchanges at the local scale, there is a crucial need to develop innovative methodologies for assessing stream-aquifer exchanges at the regional scale. After formulating the conductance model at the regional and intermediate scales, we address this challenging issue with the development of an iterative modelling methodology, which ensures the consistency of stream-aquifer exchanges between the intermediate and regional scales.Finally, practical recommendations are provided for the study of the interface using the innovative methodology MIM (Measurements-Interpolation-Modelling), which is graphically developed, scaling in space the three pools of methods needed to fully understand stream-aquifer interfaces at various scales. In the MIM space, stream-aquifer interfaces that can be studied by a given approach are localised. The efficiency of the method is demonstrated with two examples. The first one proposes an upscaling framework, structured around river reaches of ∼ 10-100 m, from the local to the watershed scale. The second example highlights the usefulness of space borne data to improve the assessment of streamaquifer exchanges at the regional and continental scales. We conclude that further developments in modelling and field measurements have to be undertaken at the regional scale to enable a proper modelling of stream-aquifer exchanges from the local to the continental scale.

“…According to Beven (2000Beven ( , 2006a, Beven et al (2011) and, the importance of uniqueness of place and the limitations of hydrological data can, in most cases, make parameter allocation rather difficult, and so we should consider the limitations of current concepts. As mentioned by Beven in his referee comment, in practice we are both model and data limited, and even a perfect model will be limited by inconsistencies in the calibration and prediction data (e.g., Beven and Smith, 2014) -so that the success or failure of a model run with a priori parameter estimates might depend more on the (unknown) errors in the data than on whether the model is a realistic representation of the processes.…”

mentioning

confidence: 99%

HESS Opinions: Advocating process modeling and de-emphasizing parameter estimation

Bahremand

2016

Abstract. Since its origins as an engineering discipline, with its widespread use of "black box" (empirical) modeling approaches, hydrology has evolved into a scientific discipline that seeks a more "white box" (physics-based) modeling approach to solving problems such as the description and simulation of the rainfall-runoff responses of a watershed. There has been much recent debate regarding the future of the hydrological sciences, and several publications have voiced opinions on this subject. This opinion paper seeks to comment and expand upon some recent publications that have advocated an increased focus on process-based modeling while de-emphasizing the focus on detailed attention to parameter estimation. In particular, it offers a perspective that emphasizes a more hydraulic (more physics-based and less empirical) approach to development and implementation of hydrological models.