Determining the threshold value of surface runoff of South Koel River basin, Eastern India

The present study is an attempt to understand the surface runoff threshold phenomena of the South Koel River basin. The hydrological response unit-specific outputs of the Soil and Water Assessment Tool hydrological model for forest cover, agricultural land, and urban built-up area were used as input datasets for the study. Then, a one-way analysis of covariance model was used to capture the runoff sensitivity to changes in the aforementioned three land use and land cover classes. The results show that the threshold value of forested land, beyond which surface runoff begins to change significantly, is 1.35 km2. Similarly, the threshold value for agricultural land size is found to be 1.30 km2. In contrast, the built-up area exhibited insensitivity to alterations in surface runoff due to its limited coverage and scattered distribution. The findings can be applied for the formulation of effective strategies in water resource management.