The Revised Curve Number Rainfall–Runoff Methodology for an Improved Runoff Prediction

The Curve Number (CN) rainfall–runoff model is a widely used method for estimating the amount of rainfall and runoff, but its accuracy in predicting runoff has been questioned globally due to failure produce precise predictions. was developed by United States Department Agriculture (USDA) Soil Conservation Services (SCS) 1954, data documentation about development are incomplete, making it difficult reassess validity. originally using 1954 dataset plotted USDA on log–log scale graph, with proposed linear correlation between two key variables (Ia S), given Ia = 0.2S. However, instead antilog equation power form S0.2) simplification, 0.2S formulate current SCS-CN model. To date, researchers have not challenged this potential oversight. This study reevaluated CN testing reliability performance from Malaysia, China, Greece. results showed that can be formulated improved S?. Nash–Sutcliffe efficiency (E) indexes ranged 0.786 0.919, while Kling–Gupta Efficiency (KGE) 0.739 0.956. S ratios (Ia/S) were range [0.009, 0.171], which line worldwide reported ratio mostly 5% or lower nowhere near value 0.2 (20%) suggested SCS.