Relationship between Runoff Curve Number and PET

Abstract

This paper presents a relationship between the runoff curve number (CN) and mean potential evapotranspiration (PET) using longterm daily rainfall-runoff data. To this end, CNs were derived for different durations from rainfall-runoff data of eight different agro-climatic river basins in India, and these were correlated with PET derived for respective watersheds using the standard Penman-Monteith method. The resulting high coefficient of determination (R2) values, viz, 0.99 for Hemawati and Mohegoan; 0.98 for Haridanagar, Kalu, and Seonath; 0.96 for Manot, Ghodahadho, and Ramganga strongly support the versatility of the derived relationship. This relationship also invokes determination of PET from the available published CN values, and therefore may be quite useful in field applications.