Improved CN-Based Long-Term Hydrologic Simulation Model

AbstractEmploying the advanced soil moisture accounting (ASMA) procedure and the modified subsurface drainage flow concept, a curve number (CN)–based model, named as modified long-term hydrologic simulation advance soil moisture accounting (MLTHS ASMA) model, is proposed to simulate daily flows. Its application to 17 watersheds falling in different agro-climatic zones of India and comparison with the existing long-term hydrologic simulation advance soil moisture accounting (LTHS ASMA) model reveal that the proposed model yields higher efficiency, lower standard error of estimate (SE) and percentage relative error (RE) values for high runoff producing wet watersheds, and lower efficiency for low runoff producing dry watersheds, indicating a very good model response to wet watersheds, and good to satisfactory-to-dry watersheds. On most watersheds, the proposed model performed better than the existing one. In addition, CN parameters for surface and subsurface flows were most sensitive followed by the parameters related with soil characteristics, and the significance of base flow was greater in wet watersheds than in dry watersheds.