ABSTRACT
The hydrologic characteristics of an arid or semi-arid region are determined largely by its climate, geology, and geography. The climatic factors that establish the hydrologic features of these regions include the amount and distribution of precipitation and the effects of wind, temperature, and humidity on evaporation and evapotranspiration. Meteorology plays an important role in hydrologic problems such as determining probable maximum precipitation conditions for spillway design, forecasting precipitation for reservoir operation, and determining probable maximum winds over water surfaces (used for evaluating the resulting waves in connection with the design of dams and levees). Obviously, a hydrologist should have some understanding of the meteorological processes that determine a regional climate. The general features of climatology and climate change are discussed in this chapter.
