8-Relative significance of various factors in lake evaporation - A case study using principal component analysis

Abstract

Evaporation in lakes is influenced by various factors such as temperature, radiation, atmospheric pressure, wind, sunshine hours, relative humidity, water quality etc. However, relative significance of the various factors in the process of lake evaporation is not known. There are hardly any reported studies on this aspects. The present study has been carried out for Pichhola Lake which is located in Udaipur in the state of Rajasthan in India. The major objective of the study is to identify some of the important variables that influence the process of lake evaporation and their relative significance for the process. A multivariate statistical technique namely principal component analysis has been used for the purpose. Five years of daily data (2002-2006) relating to eight variables viz. maximum temperature, minimum temperature, mean temperature, maximum relative humidity, minimum relative humidity, mean relative humidity, bright sunshine hours and wind were analyzed for the study. The results of study indicate that three factors having dominance of temperature, relative humidity and wind respectively, control the evaporation from the lake. Out of the three the first two factors are very significant as they explain about 85 percent of the total variance in the original data. The first factor explains about 39 % and the second factor explains about 45 percent of the total variance. The three factors together explain about 97 percent of the total variance. Detailed analysis of the principal factors based on varimax factor rotation technique brings out the fact that lake evaporation is a combined effect of temperature, relative humidity (vapour pressure) and wind, with temperature and relative humidity (vapour pressure) being relatively highly significant than the wind. The study is useful in understanding the process of lake evaporation in a better way.