Runoff Curve Numbers for Peat-Dominated Watersheds

Abstract

AbstractThe natural resources conservation service (NRCS) curve number method is widely used to estimate runoff from rainfall events for four hydrological soil groups (A, B, C, and D). However, the NRCS soil groups do not yet include peat soils. Therefore, this study analyzed 59 rainfall-runoff events from two peat-dominated watersheds in Finland (Marjasuo, Royvansuo) and one in Norway (Grualia). The analysis used the United States Army Corps of Engineers Hydrologic Engineering Center Hydrologic Modeling System (HEC-HMS) to calibrate curve numbers and initial abstraction ratios (Ia/S). This gave a mean Ia/S of 0.036, with a mean standard error of 0.003 and 95% confidence interval of 0.030–0.042, which is significantly lower than the value of 0.2 recommended in the NRCS curve number method. The mean curve number was 61, with a mean standard error of 0.9 and 95% confidence interval of 59–63 for the study watersheds. This study confirmed that application of the NRCS curve number method in HEC-HMS required se...