Study of surface evaporation in a semi-arid region

Water resources management plays a significant role in the development of any country. Many areas of the world are arid and semi-arid. The water loss due to evaporation and evapotranspiration is the major problem in these regions. The problem caused by the loss of water stored in lakes and reservoirs for irrigation and domestic use by evaporation during the summer months in these regions is enormous and perennial. In India the estimated area of arid, semiarid and long dry spell regions is about 200,000 km 2 (Ramdas, 1966). The annual water loss due to evaporation with estimated depth of 3 m is of the order of 1.32*10 12 gallons (Verma, 1996) in India. Therefore estimation of evaporation and evapotranspiration are required in the design of reservoirs, irrigation systems, scheduling and frequency of irrigation, water balance and simulation studies and watershed planning and management. In this paper, Pan and Penman methods of estimating surface evaporation at Annamalainagar, TamilNadu, India, were studied and results were compared and presented. The study area is a semi-arid region, plain delta and lightly vegetated with mainly paddy crops. This study undertakes to analyse the methods of estimating evaporation so that suitable values of evaporation can be applied at the time of water management and reservoir operation practices. The regression and correlation analysis was carried out between the Pan and Penman evaporation values. Also Penman evaporation was related to evapotranspiration.