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The Use of Asymptotic Functions for Determining Empirical Values of CN Parameter in Selected Catchments of Variable Land Cover

Abstract

The aim of the study was to assess the applicability of asymptotic functions for determining the value of CN parameter as a function of precipitation depth in mountain and upland catchments. The analyses were carried out in two catchments: the Rudawa, left tributary of the Vistula, and the Kamienica, right tributary of the Dunajec. The input material included data on precipitation and flows for a multi-year period 1980–2012, obtained from IMGW PIB in Warsaw. Two models were used to determine empirical values of CN obs parameter as a function of precipitation depth: standard Hawkins model and 2-CN model allowing for a heterogeneous nature of a catchment area.

The study analyses confirmed that asymptotic functions properly described P-CN obs relationship for the entire range of precipitation variability. In the case of high rainfalls, CN obs remained above or below the commonly accepted average antecedent moisture conditions AMCII. The study calculations indicated that the runoff amount calculated according to the original SCS-CN method might be underestimated, and this could adversely affect the values of design flows required for the design of hydraulic engineering projects. In catchments with heterogeneous land cover, the results of CN obs were more accurate when 2-CN model was used instead of the standard Hawkins model. 2-CN model is more precise in accounting for differences in runoff formation depending on retention capacity of the substrate. It was also demonstrated that the commonly accepted initial abstraction coefficient λ = 0.20 yielded too big initial loss of precipitation in the analyzed catchments and, therefore, the computed direct runoff was underestimated. The best results were obtained for λ = 0.05.

Open access
The Importance of Benchmarking in the Innovative Activities of Tourism Enterprises: The Case Study of Lot S.A. Polish Airlines

Abstract

The aim of this article is to identify the importance of benchmarking as a source of innovation in the activities of tourism enterprises through the case study of LOT S.A. Polish Airlines. To expand, the objective was to identify the departments within the company which used benchmarking as a stimulus to create a new or improve an existing offer. The subject was an airline belonging to Star Alliance and 27 employees from selected departments. The study used questionnaires and. with managers of selected departments only, open standardized interviews. Statistical inference methods, including a chi-square test, were applied to analyse the data. Although the introduction of benchmarking in the company’s structure allows for a quick escape route from a cycle of limitation in the company’s own culture and standard behaviour (and the acquisition of knowledge during the process gives rise to new and innovative ideas) the importance of this method in innovative activities did not result in any practical application. A lack of knowledge about benchmarking was noticeable, and an identification of this method with a simple competitive analysis resulted in failures in business activity as well as a lack of creativity in its application.

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