Due to rapid growth of the world population and increase in water demands for agriculture, industry and urban development, it is necessary to plan for improving water resources management. Recently, more attention has been paid to develop the green areas around the cities, in order to alleviate air pollution and provide better environmental conditions. Allocation of new water sources for landscape development, especially in arid areas, is difficult because of the water shortage. Estimation of evapotrairation of green areas is essential in planning, design and management of irrigation and drainage projects. Potential evapotrairation of common plants in landscapes including two grasses (Lolium perenne and sport (Lolium perenne, Festuca rubra L. and Poa pratensis L.)) and two tree types (Fraxinus rotundifolia and Cupressus arizonica) was estimated using drainage lysimeters, installed in Mahmoudabad Research Center, Isfahan, Iran-during 2004-2005. Three replications were used for each grass or tree. Lysimeters had dimensions of 150×100×120 cm. They were installed in the middle of the experimental field, surrounded by similar grasses or trees to a distance of 30×50 m. The results showed that 8-month water need of these plants was 1834, 1937, 983 and 837 mm for sport grass, Lolilium perenna, Fraxinus rotundifolia and Cupressus arizonica, respectively. The ratio of Lolilium perenna to sport grass evapotrairation was 1.055 for the whole growth period. Mean crop coefficient for Fraxinus rotundifolia was obtained as 0.48, with maximum of 0.77 in August and minimum of 0.2 in April. Mean crop coefficient for Cupressus arizonica was obtained as 0.43, with maximum of 0.58 in July and minimum of 0.3 in April. Also, Class-A Pan evaporation, with coefficient Kp, was determined to be the best method for estimation of reference-rop evapotrairation in Isfahan region. Other methods such as modified Blaney-Criddle, FAO-Radiation, FAO 56-Penman, Turc, FAO 24-Penman, Hargreaves-1985, Penman-Kimberly 1996, Makkink-1957 and Priestly-Taylor ranked next.
