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SENSITIVITY ANALYSES OF CONCEPTUAL AND SEMIDISTRIBUTED HYDROLOGICAL MODELS APPLIED OVER A PILOT BASIN

Silviya Stoyanova

Abstract

Mathematical modelling is a powerful tool when it comes to studying and solving complex hydrological problems ? studying the hydrological regime in a changing environment, hydrological forecasting, flood risk estimation and etc. There are different types of hydrological models depending on their characteristics and an in-depth knowledge is needed to use the most appropriate one for a given purpose, e.g. evaluation, planning, forecasting. Indispensable part of building a trustworthy hydrological model is performing a sensitivity analysis towards identifying those input parameters that make a substantial change in the model output when changed unsubstantially. Input model parameters are the tool for describing the hydrological regime of the system being modelled and a sensitivity analysis shows the most important processes in the study area. In this paper input parameter estimation for surface water modelling is suggested as an approach for identifying the most suitable hydrological model to be used in a pilot basin. For this study the MIKE 11 NAM model and the Soil and Water Assessment Tool were used. MIKE 11 NAM model is a lumped, conceptual, rainfall-runoff model. The Soil and Water Assessment Tool is an open source watershed scale, semi-distributed hydrological model. Sensitivity analysis for the MIKE 11 NAM model was performed towards simulated and observed data manually. The one-factor-at-a-time design method was used and three objective functions were applied: Nash-Sutcliffe coefficient (NSC), correlation coefficient (R?) and sum of the squares of the residuals (SSQ). Sensitivity analysis for the Soil and Water Assessment Tool was also performed towards simulated and observed data using however an automated built-in tool. The Latin-Hypercube One-factor-At-a-Time method (van Griensven et al., 2006) and the sum of the squares of the residuals (SSQ) objective function were applied. The target of this study is to find the sensitive parameters for each of the hydrological models when applied over the pilot basin, thus defining the use of the hydrological models regarding solving certain hydrological problems. Data from the sensitivity analyses has been processed and statistical information, results and conclusions are to be presented in this paper.

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DOI resolver: doi.org/10.5593/sgem2019/3.1/s12.066

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