Estimation of monthly average pet by various methods and its relationship with pan evaporation at Bhagalpur, Bihar

Abstract

Mesh covered pan evaporation at Bhagalpur was correlated with potential evapotranspiration (PET) computed by using empirical methods of FAO-Penmann Monteith (1998), Thornthwaite (1948), Papadakis (1965), Jensen and Haise (1963) and Modified Jenson and Haise (1975). Weather data for 4 years namely 2014-2017 for Bhagalpur was used to compute the potential evapotranspiration by different empirical methods. Linear regression equations were fitted between monthly PET by computed by different individual methods and the measured pan evapotranspiration. Pan evaporation showed good correlation with monthly PET having R2 value of 92.8 for Jensen and Haise, 91.8 for modified Jensen and Haise, 90.8 for FAO-Penmann Monteith and moderate correlation was observed in case of Thorntwaite (58.7) and Papadkais Method (61.4). There exists biasness between estimated and observed pan evaporation. The biasness was positive when pan evaporation was on the higher sides and biasness was negative when the pan evaporation was on the lower side.