ENVE-205 Environmental Engineering Hydrology

CHAPTER IV: Evapotranspiration

In this chapter, evaporation from water surfaces and transpiration from plants will be discussed. Relationship of Class A pan measurements to surface water evaporation will be examined.

Study Plan:

· Learning the factors affecting evaporation (Section 4.1).

· Learning the structure of Class A pans (see figure) for evaporation measurements (Section 4.1.1).

· Learning the use of water budget technique for evaporation calculations (Section 4.1.2).

· Learning some empirical formulations for evaporation estimation using climatic data and using the Kohler plots for evaporation determination depending on wind speed, elevation, temperature difference between air and surface water, and measured pan evaporation (Section 4.1.3).

· Discussing the plant transpiration phenomenon and learning some empirical evapotranspiration relations such as Thornthwaite equation and Blaney and Criddle equations (Section 4.2).

· Example problems 4.1.

· Homework problems 1, 2, 3, 5, 6, 8.