DBPapers
DOI: 10.5593/sgem2017H/33/S12.010

ASSESSMENT OF THE UNCERTAINTIES OF THE VALUES OF A HYDROLOGIC MODEL PARAMETERS TAKING INTO ACCOUNT TWO CALIBRATION APPROACHES

P. Sleziak, J. Szolgay, K. Hlavcova, J. Parajka
Thursday 23 November 2017 by Libadmin2017

References: 17th International Multidisciplinary Scientific GeoConference SGEM 2017, www.sgemviennagreen.org, SGEM2017 Vienna GREEN Conference Proceedings, ISBN 978-619-7408-27-0 / ISSN 1314-2704, 27 - 29 November, 2017, Vol. 17, Issue 33, 75-82 pp; DOI: 10.5593/sgem2017H/33/S12.010

ABSTRACT

Reliable estimates of water balance components are important for solving various tasks in water management, such as hydropower management, flood forecasting, etc. It is well known that the modeling of the water balance components is associated with several problems, e.g., uncertainty in inputs, model parameters and model structure. Considering various data sources in the parameter estimation process can be a good way to improve model consistency and also to reduce parameter uncertainty.
The objective of this study is to assess the value of additional information in multi-objective calibration in terms of uncertainties of the values of the model parameters. We are particularly interested in investigating how the uncertainty of parameter values changes when moving from the single-calibration approach to the multi-calibration approach. This study was performed in two large groups of Austrian catchments (i.e., catchments with a dominant snow and soil moisture regime) that were delineated by a parameter sensitive study. For the modeling purposes a lumped conceptual rainfall-runoff model (TUW model) was used. This model was calibrated between 1981 – 1990 and 2001 – 2010 using two objective functions, i.e., the single-objective function (termed SINGLE) that involves only values from one measured process (i.e., runoff) and multi-objective function (termed MULTI) that involves values from two measured processes (i.e., runoff and snow cover). The parameter uncertainty was assessed by the coefficient of determination (r2). We found that the parameters with smaller uncertainties of the values in both calibration approaches are, e.g., the fast storage coefficient (k1) and the percolation rate (Cperc). To the contrary, the parameters with larger uncertainties of the values are, e.g., the threshold air temperatures (Tr, Tm).
Subsequently, we investigated how the uncertainty of parameter values changes when moving from the SINGLE to the MULTI approach. The results showed that the r2 increases only for parameters related to the snow module of the TUW model. (i.e., degree-day meld parameter DDF, threshold temperatures Tr and Ts). This means that, if snow data are used in calibration (the MULTI approach) it is mainly the snow component of the model that could be improved. Some of the comparisons of the uncertainties of the values of the model parameters are discussed in conclusion.

Keywords: TUW model, parameter uncertainty, multi-objective calibration, Austria