ENVE-205 Environmental Engineering Hydrology

CHAPTER III: Precipitation

In this chapter, precipitation and the factors effective on its formation, such as meteorology, weather systems, and microphysical properties are presented. Interpretation and quantification of precipitation data are discussed. Some average watershed precipitation calculation techniques are presented. Extrapolation of point measurements to watersheds through rational equation is discussed. The use of intensity-duration-frequency (IDF) curves is presented.

Study Plan:

· Learning the basic definition of meteorology and concepts of atmosphere, water vapor, solar energy, wind, and temperature (Section 3.1).

· Learning the structures of major weather systems such as convective storms, orographic storms, cyclonic storms, and tropical cyclones (Section 3.2).

· Learning the precipitation formation mechanism, precipitation classification, water quality of precipitation, and eutrophication phenomenon (Section 3.3).

· Learning some precipitation measurement techniques and missing data treatment methods such as arithmetic average and normal-ratio methods (Sections 3.4.1, 3.4.4).

· Learning the concepts of hyetograph formation, cumulative rainfall diagram, duration determination of a precipitation event, and dimensionless cumulative rainfall diagram (Section 3.5).

· Learning the isohyetal, Thiessen, and arithmetic average methods for average watershed precipitation calculations (Section 3.6).

· Learning the use of rational equation for extrapolation of point measurements to areal watershed calculations (Section 3.7).

· Learning the formation and use of intensity-duration-frequency (IDF) curves (Section 3.8).

· Example problems 3.1, 3.2, 3.3, 3.4.

· Homework problems 1, 2, 3, 4, 5, 6, 8, 9, 11, 12, 14, 15, 16, 18, 22, 25.