Simulating the Influence of Crop Cultivation Practices and Slope Gradients on Curve Number and Runoff Generation in Semi-arid Flat Catchments

An experiment was conducted over three years (2019–2021) at the Junagadh Agricultural University campus farm during the monsoon season. Thirteen treatments were examined in standard runoff-soil erosion measurement plots, including various bed slopes (0.50, 0.75, and 1.00%), crops (groundnut and cotton), and cultivation practices (along and across the slope), along with a control plot. Rainfall and runoff events were measured separately for each treatment. The curve number (CN) was estimated using the soil conservation service curve number (SCS-CN) model based on average antecedent moisture. The results showed higher runoff depth and coefficient in along-the-slope cultivation practices and steeper slopes. Cotton crops exhibited higher runoff depth compared to groundnut crops. The study highlighted lower CN values in across-the-slope cultivation for both crops. The derived CN values will aid in estimating runoff by the SCS model for cotton and groundnut crops across various land slopes. The proposed model, establishing a relationship between average CN and slope, demonstrated remarkable accuracy with R2, Nash–Sutcliffe efficiency, and root mean square error values approaching unity. Despite a slight underestimation (negative bias), the model provided reliable predictions. These findings have far-reaching implications, offering valuable insights for researchers and policymakers in designing effective soil and water conservation measures for flat micro-catchment areas. The study significantly advances the understanding of runoff generation and enhances the precision of runoff prediction models. © The Institution of Engineers (India) 2024.