Probabilistic properties of a curve number: A case study for small Polish and Slovak Carpathian Basins

• DOI: 10.1007/s11629-014-3123-0
• Publication Date: 2015-05-30T22:16:55Z
• Authors: Agnieszka Rutkowska; Silvia Kohnová; Kazimierz Banasik; Ján Szolgay; Beata Karabová
• Keywords: 0208 environmental biotechnology; 02 engineering and technology; 6. Clean water

The proper determination of the curve number (CN) in the SCS-CN method reduces errors in predicting runoff volume. In this paper the variability of CN was studied for 5 Slovak and 5 Polish Carpathian catchments. Empirical curve numbers were applied to the distribution fitting. Next, theoretical characteristics of CN were estimated. For 100-CN the Generalized Extreme Value (GEV) distribution was identified as the best fit in most of the catchments. An assessment of the differences between the characteristics estimated from theoretical distributions and the tabulated values of CN was performed. The comparison between the antecedent runoff conditions (ARC) of Hawkins and Hjelmfelt was also completed. The analysis was done for various magnitudes of rainfall. Confidence intervals (CI) were helpful in this evaluation. The studies revealed discordances between the tabulated and estimated CNs. The tabulated CNs were usually lower than estimated values; therefore, an application of the median value and the probabilistic ARC of Hjelmfelt for wet runoff conditions is advisable. For dry conditions the ARC of Hjelmfelt usually better estimated CN than ARC of Hawkins did, but in several catchments neither the ARC of Hawkins nor Hjelmfelt sufficiently depicted the variability in CN.